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【redis的学习与使用】

食用级别：初级 & 中级

学习视频：狂神

redis定义与介绍：

Redis基于内存运行并支持持久化的NoSQL数据库，也被称为数据结构服务器

string 是 redis 最基本的类型，一个 key 对应一个 value。

string 类型是二进制安全的。意思是 redis 的 string 可以包含任何数据。比如jpg图片或者序列化的对象。

string 类型是 Redis 最基本的数据类型，string 类型的值最大能存储 512MB。

Redis默认使用6379通信端口。

redis特点：

性能优秀，数据在内存中，读写速度非常快，支持并发 10W QPS。
单进程单线程，是线程安全的，采用 IO 多路复用机制。
丰富的数据类型，支持字符串（strings）、散列/哈希（hashes）、列表（lists）、集合（sets）、有序集合zset（sorted sets）等。
支持数据持久化。

可以将内存中数据保存在磁盘中，重启时加载。
主从复制，哨兵，高可用。
可以用作分布式锁。
可以作为消息中间件使用，支持发布订阅。

参考：https://www.cnblogs.com/it-deepinmind/p/14252804.html

为什么可以用redis作为mysql的缓存配合使用：

因为mysql存储在磁盘里，redis存储在内存里，redis既可以用来做持久存储，也可以做缓存，而目前大多数公司的存储都是mysql + redis，mysql作为主存储，redis作为辅助存储被用作缓存，加快访问读取的速度，提高性能

（个人理解：组原里应该提过，内存的读取速度是远远快于磁盘的，但是全用内存又成本太高，所以采用这样一种内外结合的方式，需要注重性能的地方使用redis，不需要的用mysql即可）

这同样解释了为什么redis不使用多线程（不过现在的redis6已结开始支持多线程了），它是基于内存操作的，和CPU没有什么关系，多线程也不会让其效率得到提升，可能还会出现各种问题。

至于它为什么这么快：一个是语言原因，redis是C开发的，C的速度很快，一个就是没有多线程导致的复杂处理情景

redis6.0——新特性之一：多线程

redis6多线程只是用来处理网络数据的读写和协议解析上，底层数据操作还是单线程
执行命令仍然是单线程，之所以这么设计是不想因为多线程而变得复杂，需要去控制key、lua、事务、LPUSH/LPOP等等的并发问题
官网上提到，某场景下使用多线程可以提高一倍的效率（自身没有用到redis6，所以只是提一句，redis6的特性来源网络，好多一样的，我也不知道谁参考谁。。）

为什么要用redis：

这个主要是要考虑性能和并发，高并发下，大量请求访问（冲击）数据库，会导致访问异常，redis可以作为缓冲。还有上面说的，整体上可以拉高一些读取速度。

另外redis还可以作为消息中间件（消息发布与订阅等等）

总结来说：三个作用：缓存，数据库，中间件

redis的一些命令行操作：

java的redis缓存操作其实也和命令行大同小异，这里先了解一下命令行下的各种操作：

redis默认有16个数据库，一般都会默认存在第一个数据库，我们可以通过select来切换数据库

keys * 操作查看当前所有的key，比如3库中的"name"，然后可以通过get name 来获取“name”的value值

清空操作：flushall或者flushdb，注意，这些是清空数据库而不是界面，，和mysql很不一样的（当然大部分人都没有相关的权限，不然.....）

EXISTS name　　　如果key存在则返回1

move name 　　　　移除key

 利用expire设置KEY过期时间 ，10s ，ttl可查看剩余时间；

type name 查看key【name】的数据类型

setex 可以设置键值并同时设置key的过期时间

 mset可以批量创建；同理，mget可以批量获取keys；

setnx：与set不同的是，setnx k1 v1 的时候若k1已经存在则报错，不存在则正常创建；

msetnx：批量创建，具有原子性，也就是一致性，比方说，msetnx k1 v1 k4 v4 其中k1已存在，k4不存在，所以批量创建会失败，只要有一个已存在就会整体失败。

 getset操作：先查询后更新，查不到会返回null，但是更新操作会生效，如上图；

除了String类型，List，set，hash，zset 这四种类型是最常用的：

【List】

 redis中list 可以左插入或是右插入（类似于队列），比如 有这样一排座位，只从左侧开始，1号队友先坐了左数第一个座位，但是一会儿二号又来了，没办法，1号只能往右边挪一个位置，所以这样子，如图，list 中最左边的元素应该是最后一个插入的；Pop操作也很好理解，可以左右出列 。同样，右插，rpush同理（注意，是没有rrange这种东西的）；

lindex 操作获取list中的某个特定下标对应的元素

 Llen list 操作 #获取list长度

删除特定的值：

　　List与set不同，是可以允许重复值存在的，所以利用 lrem 可以移除多个value

图中数字很多，可能没有辨识度，但是当你输入的时候redis会有提示的，比如：

如图，我remove了两个特定value“3”，精确匹配

trim 截取操作， 如图，我截取了0到1 ，即前两个值（左数）

ropolpush list otherlist 　　移除list的最后一个元素（最右），存入一个新list中

同样的，如果列表下标存在值，可以对此下标进行 lset操作，进行value更新；

　　　　可以通过 linsert 来实现插入，通过before和after来控制插入位置

【set】

set里面的插入操作为sadd

查询集合成员：smembers

取交集 sdiff ; 取并集 sunion;

【hash】

和String操作类似，只不过用K-V取代了V

hset 添加

hget 获取

hmset　　set多个k-v

hmget　　get多个k-v

hgetall　　获取所有

hdel　　　删除指定的hash key(对应的value会自动被删除)

hkeys　　获取所有的keys

hvals　　获取所有的values

【zset】即sortset

同set，有zadd

以及有序排列

当元素存在时zadd则起到更新的作用；

这里面zrangebyscore 的score是redis自带的

也可以限定范围进行排序

【geospatial地理位置】

　　同时geo也是一种特殊数据类型。

　　通过geoadd可以给一个key添加多个位置节点（注意是先经度后维度）

　　利用geodist：计算两个位置节点之间的距离

　　georadius：根据用户给定的经纬度坐标来获取指定范围内的地理位置集合，注意距离 10 km 的数字和单位中间间隔一个空格

　　geopos 用于从给定的 key 里返回所有指定名称(member)的位置（经度和纬度），不存在的返回 nil。

　　georadius 以给定的经纬度为中心，返回键包含的位置元素当中，与中心的距离不超过给定最大距离的所有位置元素。

　　georadiusbymember 和 GEORADIUS 命令一样，都可以找出位于指定范围内的元素，但是 georadiusbymember 的中心点是由给定的位置元素决定的，而不是使用经度和纬度来决定中心点。

　　geohash：返回一个或多个位置对象的 geohash 值。

　　测试demo如下：

[root@iZbp1hwh629hd4xz80i1z0Z bin]# redis-cli -p 6379
127.0.0.1:6379> geoadd china:city 116.9038723847656 39.66750041446214 beijing
(integer) 1
127.0.0.1:6379> geoadd china:city 91.13775 29.65262 lasa
(integer) 1
127.0.0.1:6379> geodist testkey beijing lasa
(nil)
127.0.0.1:6379> geoadd testkey  116.9038723847656 39.66750041446214 beijing
(integer) 1
127.0.0.1:6379> geoadd testkey  91.13775 29.65262 lasa
(integer) 1
127.0.0.1:6379> geodist testkey beijing lasa
"2594695.6553"
127.0.0.1:6379> georadius testkey 116 39 10km
(error) ERR wrong number of arguments for 'georadius' command
127.0.0.1:6379> georadius testkey 116 39 100km
(error) ERR wrong number of arguments for 'georadius' command
127.0.0.1:6379> georadius testkey 116 39 10 km
(empty list or set)
127.0.0.1:6379> georadius testkey 116 39 100 km withdist
(empty list or set)
127.0.0.1:6379> geoadd testkey  117 39 tianjin
(integer) 1
127.0.0.1:6379> geodist testkey beijing tianjin
"74702.7948"
127.0.0.1:6379> georadius testkey 117 39 10 km withdist
1) 1) "tianjin"
   2) "0.0002"
127.0.0.1:6379> georadius testkey 117 39 100 km withdist
1) 1) "tianjin"
   2) "0.0002"
2) 1) "beijing"
   2) "74.7027"
127.0.0.1:6379> georadius testkey 117 39 20 km withdist
1) 1) "tianjin"
   2) "0.0002"
127.0.0.1:6379> geopos testkey beijing nonexisting
1) 1) "116.90387338399887085"
   2) "39.66750025860940099"
2) (nil)
127.0.0.1:6379> georadius testkey 117 38.8 20 km withdist
(empty list or set)
127.0.0.1:6379> georadius testkey 117 38.8 200 km withdist
1) 1) "tianjin"
   2) "22.2452"
2) 1) "beijing"
   2) "96.8436"
127.0.0.1:6379> georadiusbymember testkey beijing  200 km withdist
1) 1) "tianjin"
   2) "74.7028"
2) 1) "beijing"
   2) "0.0000"
127.0.0.1:6379> geohash testkey beijing lasa
1) "wx51sjnzcw0"
2) "wj2b9yh7p20"
127.0.0.1:6379>

PS：根据百度地图-工具箱-测距来计算，拉萨-北京距离为2558600米，和redis计算结果2594695.6553，大致相同，数据不同可能是坐标原点取值不同？

【Hyperloglog——统计基数利器】

　　 Hyperloglog也是一种特殊的数据类型。

　　适用于需要计算大量不同特征数据个数的需求，比如统计不同用户访问网站，多个人访问同一个网站，只需要计入一次；传统方法是利用set存储统计，而Hyperloglog 的优势就是不存储，只计算，这样就节省了很多内存空间。

　　测试代码：

127.0.0.1:6379> pfadd pfkey zoe louis nick coach zoey zoe
(integer) 1
127.0.0.1:6379> pfcount pfkey
(integer) 5
127.0.0.1:6379>

【Bitmap】

　　一种redis 的特殊数据类型。

　　是用0,1二进制对立方式来存储记录的，例如记录一周内的打卡与否：

　　示例如下：

127.0.0.1:6379> setbit bitkey 1  1
(integer) 0
127.0.0.1:6379> setbit bitkey 2 0
(integer) 0
127.0.0.1:6379> setbit bitkey 3 1
(integer) 0
127.0.0.1:6379> setbit bitkey 4 1
(integer) 0
127.0.0.1:6379> getbit bitkey 3
(integer) 1
127.0.0.1:6379> bitcount bitkey 
(integer) 3
127.0.0.1:6379> bitcount bitkey 1 3
(integer) 0
127.0.0.1:6379> bitcount bitkey [1 3]
(error) ERR value is not an integer or out of range
127.0.0.1:6379> bitcount bitkey 1 3
(integer) 0
127.0.0.1:6379> bitcount bitkey 0 2
(integer) 3
127.0.0.1:6379> bitcount bitkey 1 2
(integer) 0
127.0.0.1:6379>

　　值得注意的是，bitcount 指令是统计字节数组中对应1的个数，拿上面bitkey中的数据为例，目前下标 0,1,2,3 四个位置上存有数据，

　　第一个元素存储是1，即对应 01000000 （除去第一位后的第一个置为1），1,2,3同理，存储后如下：01011000 。

　　所谓指令 bitcount bitkey 1 3 ，是统计 01011000 00000000 00000000 00000000 这四个部分对应第二个到第四个有多少个1 ，结果是0；

　　而 bitcount bitkey 0 2，是统计上面四个中的前三个 01011000 00000000 00000000 有几个1，结果是 3个；

　　当然，就结果而言，可以理解为使用bitcount keyname 可直接统计内存中元素为1 的个数。

【redis的基本事务操作】

　　redis一个事务可以一次执行多个命令，或者说是一组，然后这一组命令都会被序列化，事务执行过程中，命令会顺序执行（exec前均不会执行）。

　　其有如下三个性质：

批量操作在发送 EXEC 命令前被放入队列缓存。
收到 EXEC 命令后进入事务执行，事务中任意命令执行失败，其余的命令依然被执行（且无回滚操作）。
在事务执行过程，其他客户端提交的命令请求不会插入到事务执行命令序列中。

　　PS：单个 Redis 命令的执行是原子性的，但 Redis 没有在事务上增加任何维持原子性的机制，所以 Redis 事务的执行并不是原子性的，事务可以理解为一个打包的批量执行脚本，但批量指令并非原子化的操作，中间某条指令的失败不会导致前面已做指令的回滚，也不会造成后续的指令不做。

　　（数据库事务的原子性：一个事务包含多个操作，这些操作要么全部执行，要么全都不执行。实现事务的原子性，要支持回滚操作，在某个操作失败后，回滚到事务执行之前的状态，也就是说）。

　 PS： redis事务也木有隔离级别的概念，（也就是没有数据脏读，重复读，幻读等危险），因为这一些列命令都是顺序执行的，而且 执行事务EXEC 这个操作后才会依次执行这一组命令。

　　redis 事务命令：

multi :事务开始
命令入队
exec：事务执行

　　测试：

127.0.0.1:6379> multi
OK
127.0.0.1:6379> set l4d1 zoey
QUEUED
127.0.0.1:6379> set l4d3 rochelle
QUEUED
127.0.0.1:6379> get l4d3
QUEUED
127.0.0.1:6379> set l4d4 zoe
QUEUED
127.0.0.1:6379> exec
1) OK
2) OK
3) "rochelle"
4) OK
127.0.0.1:6379> 

#取消事务执行

127.0.0.1:6379> multi
OK
127.0.0.1:6379> set k1 v1
QUEUED
127.0.0.1:6379> discard
OK
127.0.0.1:6379>

注意：在事务中输入命令队列时如果出现编译型异常，会导致exec时全部命令无法执行；而语法错误，比如对字符串进行加减操作时，只是错误语句无法执行而已：

实例：

127.0.0.1:6379> flushdb
OK
127.0.0.1:6379> clear
127.0.0.1:6379> set k1 "wang"
OK
127.0.0.1:6379> multi
OK
127.0.0.1:6379> incr k1
QUEUED
127.0.0.1:6379> set k2 v2
QUEUED
127.0.0.1:6379> get k2
QUEUED
127.0.0.1:6379> exec
1) (error) ERR value is not an integer or out of range
2) OK
3) "v2"
127.0.0.1:6379>

【乐观锁与悲观锁】

　　乐观锁：默认认为不会出现问题，不加锁，会在更新数据时区判断一下此期间数据是否有人修改

　　悲观锁：过于悲观，认为总有刁民要造反，无论什么行为都会加锁，此举大大影响性能

　　redis采用watch 命令来监控事务数据，当事务执行完成后监控会自动取消：

　　测试案例：

　　开启两个命令行窗口模仿并行操作：

　　如果开启监控watch后（可以通过unwatch解锁），执行事务前，通过另一个窗口（线程）去对监控变量进行操作变更，那么原窗口执行事务时就会出现错误，无法执行事务内命令。

最后，倘若事务执行失败，就先进行解锁，然后再加锁（watch）监控，然后开启事务，观察加减操作后（比如+1-1）变量值是否还是监控时的值，若相同，肯定是可以执行成功的。

redis在linux的benchmark 测试【压力测试】

redis-server kconfig/redis.conf 　　#开启服务

redis-cli -p 6379　　#然后建立连接

进入redis相关目录下

运行：redis-benchmark -h localhost -p 6379 -c 100 -n 100000 -t set 是特指测试set命令

redis-benchmark -h localhost -p 6379 -c 100 -n 100000 是测试全部命令,get、set、incr、lpush等

测试结果数据：

====== SET ======
100000 requests completed in 2.10 seconds
100 parallel clients　　　　　　#100个并发客户端
3 bytes payload　　　　　　　#每次写入3个字节
keep alive: 1　　　　　　　　#一台服务器处理（单机性能）

12.59% <= 1 milliseconds
93.36% <= 2 milliseconds
99.42% <= 3 milliseconds
99.54% <= 8 milliseconds
99.55% <= 9 milliseconds
99.57% <= 11 milliseconds
99.60% <= 12 milliseconds
99.82% <= 13 milliseconds
99.95% <= 14 milliseconds
99.95% <= 15 milliseconds
99.97% <= 16 milliseconds
100.00% <= 16 milliseconds　　　　
47596.38 requests per second　　　//10w条请求用时 2.1s左右，平均 每秒处理47596.38 条请求


[root@iZbp1hwh629hd4xz80i1z0Z bin]# redis-benchmark -h localhost -p 6379 -c 100 -n 100000
====== PING_INLINE ======
100000 requests completed in 2.12 seconds
100 parallel clients
3 bytes payload
keep alive: 1

12.79% <= 1 milliseconds
92.15% <= 2 milliseconds
99.29% <= 3 milliseconds
99.37% <= 4 milliseconds
99.38% <= 6 milliseconds
99.43% <= 7 milliseconds
99.51% <= 8 milliseconds
99.52% <= 9 milliseconds
99.60% <= 11 milliseconds
99.62% <= 12 milliseconds
99.79% <= 13 milliseconds
99.90% <= 23 milliseconds
99.92% <= 24 milliseconds
100.00% <= 25 milliseconds
47103.16 requests per second

====== PING_BULK ======
100000 requests completed in 2.06 seconds
100 parallel clients
3 bytes payload
keep alive: 1

16.59% <= 1 milliseconds
94.58% <= 2 milliseconds
99.16% <= 3 milliseconds
99.36% <= 4 milliseconds
99.39% <= 6 milliseconds
99.41% <= 7 milliseconds
99.49% <= 9 milliseconds
99.55% <= 10 milliseconds
99.57% <= 11 milliseconds
99.58% <= 12 milliseconds
99.83% <= 13 milliseconds
99.90% <= 18 milliseconds
99.95% <= 19 milliseconds
100.00% <= 19 milliseconds
48496.61 requests per second

====== SET ======
100000 requests completed in 2.12 seconds
100 parallel clients
3 bytes payload
keep alive: 1

13.89% <= 1 milliseconds
93.75% <= 2 milliseconds
99.59% <= 3 milliseconds
99.62% <= 12 milliseconds
99.78% <= 13 milliseconds
99.96% <= 18 milliseconds
99.98% <= 40 milliseconds
100.00% <= 41 milliseconds
100.00% <= 41 milliseconds
47214.35 requests per second

====== GET ======
100000 requests completed in 1.95 seconds
100 parallel clients
3 bytes payload
keep alive: 1

20.61% <= 1 milliseconds
97.57% <= 2 milliseconds
99.48% <= 3 milliseconds
99.51% <= 4 milliseconds
99.51% <= 7 milliseconds
99.57% <= 8 milliseconds
99.61% <= 11 milliseconds
99.64% <= 12 milliseconds
99.74% <= 13 milliseconds
99.86% <= 14 milliseconds
99.93% <= 18 milliseconds
100.00% <= 18 milliseconds
51282.05 requests per second

====== INCR ======
100000 requests completed in 2.10 seconds
100 parallel clients
3 bytes payload
keep alive: 1

14.50% <= 1 milliseconds
91.14% <= 2 milliseconds
99.37% <= 3 milliseconds
99.47% <= 4 milliseconds
99.50% <= 5 milliseconds
99.54% <= 7 milliseconds
99.60% <= 10 milliseconds
99.62% <= 11 milliseconds
99.62% <= 12 milliseconds
99.79% <= 13 milliseconds
99.81% <= 18 milliseconds
99.85% <= 19 milliseconds
99.90% <= 20 milliseconds
99.97% <= 21 milliseconds
100.00% <= 21 milliseconds
47528.52 requests per second

====== LPUSH ======
100000 requests completed in 2.21 seconds
100 parallel clients
3 bytes payload
keep alive: 1

9.98% <= 1 milliseconds
88.18% <= 2 milliseconds
99.11% <= 3 milliseconds
99.24% <= 7 milliseconds
99.27% <= 8 milliseconds
99.41% <= 9 milliseconds
99.44% <= 11 milliseconds
99.45% <= 12 milliseconds
99.67% <= 13 milliseconds
99.90% <= 19 milliseconds
99.91% <= 20 milliseconds
99.97% <= 21 milliseconds
100.00% <= 21 milliseconds
45269.35 requests per second

====== RPUSH ======
100000 requests completed in 2.02 seconds
100 parallel clients
3 bytes payload
keep alive: 1

15.92% <= 1 milliseconds
96.00% <= 2 milliseconds
99.51% <= 3 milliseconds
99.66% <= 4 milliseconds
99.70% <= 5 milliseconds
99.75% <= 6 milliseconds
99.76% <= 7 milliseconds
99.80% <= 10 milliseconds
99.80% <= 12 milliseconds
99.92% <= 13 milliseconds
99.98% <= 15 milliseconds
100.00% <= 15 milliseconds
49627.79 requests per second

====== LPOP ======
100000 requests completed in 2.00 seconds
100 parallel clients
3 bytes payload
keep alive: 1

15.61% <= 1 milliseconds
97.48% <= 2 milliseconds
99.55% <= 3 milliseconds
99.57% <= 6 milliseconds
99.60% <= 12 milliseconds
99.74% <= 13 milliseconds
99.78% <= 15 milliseconds
99.81% <= 16 milliseconds
99.95% <= 17 milliseconds
99.96% <= 18 milliseconds
100.00% <= 19 milliseconds
100.00% <= 19 milliseconds
50075.11 requests per second

====== RPOP ======
100000 requests completed in 2.09 seconds
100 parallel clients
3 bytes payload
keep alive: 1

13.32% <= 1 milliseconds
94.35% <= 2 milliseconds
99.27% <= 3 milliseconds
99.30% <= 5 milliseconds
99.32% <= 6 milliseconds
99.41% <= 7 milliseconds
99.51% <= 8 milliseconds
99.53% <= 9 milliseconds
99.53% <= 10 milliseconds
99.63% <= 11 milliseconds
99.68% <= 12 milliseconds
99.91% <= 13 milliseconds
100.00% <= 13 milliseconds
47824.00 requests per second

====== SADD ======
100000 requests completed in 2.09 seconds
100 parallel clients
3 bytes payload
keep alive: 1

12.97% <= 1 milliseconds
93.52% <= 2 milliseconds
99.49% <= 3 milliseconds
99.52% <= 4 milliseconds
99.53% <= 5 milliseconds
99.57% <= 6 milliseconds
99.63% <= 12 milliseconds
99.75% <= 13 milliseconds
99.80% <= 15 milliseconds
99.82% <= 16 milliseconds
99.90% <= 17 milliseconds
99.90% <= 21 milliseconds
99.96% <= 22 milliseconds
100.00% <= 22 milliseconds
47869.79 requests per second

====== HSET ======
100000 requests completed in 1.94 seconds
100 parallel clients
3 bytes payload
keep alive: 1

17.82% <= 1 milliseconds
98.41% <= 2 milliseconds
99.39% <= 3 milliseconds
99.41% <= 8 milliseconds
99.47% <= 9 milliseconds
99.56% <= 10 milliseconds
99.59% <= 11 milliseconds
99.62% <= 12 milliseconds
99.79% <= 13 milliseconds
99.90% <= 14 milliseconds
99.91% <= 15 milliseconds
99.99% <= 16 milliseconds
100.00% <= 16 milliseconds
51493.30 requests per second

====== SPOP ======
100000 requests completed in 2.03 seconds
100 parallel clients
3 bytes payload
keep alive: 1

16.54% <= 1 milliseconds
96.18% <= 2 milliseconds
99.56% <= 3 milliseconds
99.58% <= 4 milliseconds
99.59% <= 5 milliseconds
99.68% <= 8 milliseconds
99.68% <= 12 milliseconds
99.85% <= 13 milliseconds
99.96% <= 14 milliseconds
99.96% <= 18 milliseconds
100.00% <= 18 milliseconds
49333.99 requests per second

====== LPUSH (needed to benchmark LRANGE) ======
100000 requests completed in 2.08 seconds
100 parallel clients
3 bytes payload
keep alive: 1

13.43% <= 1 milliseconds
92.89% <= 2 milliseconds
99.31% <= 3 milliseconds
99.41% <= 4 milliseconds
99.48% <= 5 milliseconds
99.53% <= 9 milliseconds
99.54% <= 11 milliseconds
99.57% <= 12 milliseconds
99.78% <= 13 milliseconds
99.91% <= 19 milliseconds
99.98% <= 20 milliseconds
100.00% <= 21 milliseconds
48192.77 requests per second

====== LRANGE_100 (first 100 elements) ======
100000 requests completed in 3.56 seconds
100 parallel clients
3 bytes payload
keep alive: 1

0.06% <= 1 milliseconds
26.58% <= 2 milliseconds
77.57% <= 3 milliseconds
97.64% <= 4 milliseconds
99.14% <= 5 milliseconds
99.42% <= 6 milliseconds
99.50% <= 7 milliseconds
99.50% <= 13 milliseconds
99.55% <= 14 milliseconds
99.65% <= 15 milliseconds
99.70% <= 17 milliseconds
99.72% <= 18 milliseconds
99.81% <= 19 milliseconds
99.91% <= 20 milliseconds
99.99% <= 21 milliseconds
100.00% <= 21 milliseconds
28089.89 requests per second

====== LRANGE_300 (first 300 elements) ======
100000 requests completed in 7.86 seconds
100 parallel clients
3 bytes payload
keep alive: 1

0.03% <= 1 milliseconds
2.37% <= 2 milliseconds
10.40% <= 3 milliseconds
30.75% <= 4 milliseconds
50.12% <= 5 milliseconds
67.33% <= 6 milliseconds
82.46% <= 7 milliseconds
91.40% <= 8 milliseconds
95.38% <= 9 milliseconds
96.98% <= 10 milliseconds
97.60% <= 11 milliseconds
97.93% <= 12 milliseconds
98.15% <= 13 milliseconds
98.35% <= 14 milliseconds
98.55% <= 15 milliseconds
98.81% <= 16 milliseconds
99.03% <= 17 milliseconds
99.21% <= 18 milliseconds
99.37% <= 19 milliseconds
99.48% <= 20 milliseconds
99.57% <= 21 milliseconds
99.64% <= 22 milliseconds
99.73% <= 23 milliseconds
99.81% <= 24 milliseconds
99.86% <= 25 milliseconds
99.90% <= 26 milliseconds
99.94% <= 27 milliseconds
99.96% <= 28 milliseconds
99.97% <= 29 milliseconds
99.98% <= 30 milliseconds
100.00% <= 31 milliseconds
100.00% <= 31 milliseconds
12727.50 requests per second

====== LRANGE_500 (first 450 elements) ======
100000 requests completed in 10.73 seconds
100 parallel clients
3 bytes payload
keep alive: 1

0.00% <= 1 milliseconds
0.62% <= 2 milliseconds
2.95% <= 3 milliseconds
8.97% <= 4 milliseconds
23.15% <= 5 milliseconds
39.01% <= 6 milliseconds
53.01% <= 7 milliseconds
64.53% <= 8 milliseconds
75.86% <= 9 milliseconds
85.40% <= 10 milliseconds
91.68% <= 11 milliseconds
95.22% <= 12 milliseconds
96.73% <= 13 milliseconds
97.27% <= 14 milliseconds
97.53% <= 15 milliseconds
97.86% <= 16 milliseconds
98.25% <= 17 milliseconds
98.57% <= 18 milliseconds
98.83% <= 19 milliseconds
99.05% <= 20 milliseconds
99.30% <= 21 milliseconds
99.54% <= 22 milliseconds
99.72% <= 23 milliseconds
99.83% <= 24 milliseconds
99.87% <= 25 milliseconds
99.90% <= 26 milliseconds
99.93% <= 27 milliseconds
99.94% <= 31 milliseconds
99.95% <= 32 milliseconds
99.97% <= 33 milliseconds
99.98% <= 34 milliseconds
99.99% <= 35 milliseconds
100.00% <= 37 milliseconds
9319.67 requests per second

====== LRANGE_600 (first 600 elements) ======
100000 requests completed in 14.06 seconds
100 parallel clients
3 bytes payload
keep alive: 1

0.00% <= 1 milliseconds
0.29% <= 2 milliseconds
1.28% <= 3 milliseconds
3.29% <= 4 milliseconds
8.50% <= 5 milliseconds
19.00% <= 6 milliseconds
32.82% <= 7 milliseconds
46.16% <= 8 milliseconds
56.29% <= 9 milliseconds
64.70% <= 10 milliseconds
72.87% <= 11 milliseconds
80.98% <= 12 milliseconds
87.44% <= 13 milliseconds
92.01% <= 14 milliseconds
94.46% <= 15 milliseconds
95.70% <= 16 milliseconds
96.51% <= 17 milliseconds
97.17% <= 18 milliseconds
97.67% <= 19 milliseconds
98.00% <= 20 milliseconds
98.36% <= 21 milliseconds
98.71% <= 22 milliseconds
98.95% <= 23 milliseconds
99.17% <= 24 milliseconds
99.29% <= 25 milliseconds
99.37% <= 26 milliseconds
99.43% <= 27 milliseconds
99.53% <= 28 milliseconds
99.63% <= 29 milliseconds
99.72% <= 30 milliseconds
99.79% <= 31 milliseconds
99.82% <= 32 milliseconds
99.86% <= 33 milliseconds
99.87% <= 34 milliseconds
99.89% <= 35 milliseconds
99.90% <= 36 milliseconds
99.93% <= 37 milliseconds
99.96% <= 38 milliseconds
99.97% <= 39 milliseconds
99.98% <= 41 milliseconds
99.99% <= 42 milliseconds
99.99% <= 43 milliseconds
100.00% <= 43 milliseconds
7111.36 requests per second

====== MSET (10 keys) ======
100000 requests completed in 2.39 seconds
100 parallel clients
3 bytes payload
keep alive: 1

0.24% <= 1 milliseconds
76.53% <= 2 milliseconds
97.89% <= 3 milliseconds
98.92% <= 4 milliseconds
99.15% <= 5 milliseconds
99.22% <= 6 milliseconds
99.26% <= 7 milliseconds
99.27% <= 8 milliseconds
99.30% <= 9 milliseconds
99.46% <= 11 milliseconds
99.55% <= 12 milliseconds
99.65% <= 13 milliseconds
99.67% <= 14 milliseconds
99.73% <= 15 milliseconds
99.75% <= 16 milliseconds
99.86% <= 17 milliseconds
99.94% <= 23 milliseconds
99.97% <= 24 milliseconds
100.00% <= 24 milliseconds
41858.52 requests per second

View Code

在Java中的简单使用（radis缓存操作）：

先交代redis支持的常用数据类型：string，set，hash，list，sortsets；

并且其可通过哨兵和自动分区提高可用性（非入门，暂时不可食用）

Java操作Redis需要jedis的jar包（当前最新以及到3.7.0了）

如果需要使用Redis连接池的话，还需commons-pool-x.x.x.jar包

现在java如果想redis整合springboot，那么基本上都是用lettuce替换jedis

部分知识点参考：https://www.cnblogs.com/it-deepinmind/p/14252804.html

先简单了解下Jedis ：

　　测试demo导入依赖：

       <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>3.3.0</version>
        </dependency>
        <!--json转换依赖 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>   
　　　 　<dependency>
    　　　　<groupId>org.projectlombok</groupId>
    　　　　<artifactId>lombok</artifactId>
    　　　　<version>1.18.2</version>
　　　　</dependency>

　　　　<dependency>
   　　 　　<groupId>org.slf4j</groupId>
    　　　　<artifactId>slf4j-simple</artifactId>
    　　　　<version>1.7.25</version>
    　　　　<scope>compile</scope>
　　　　</dependency>

　　事实上在java中的命令都是我们所熟知的，在redis基础中以及学习过了：

　　【测试连接】测试我阿里云学生机的redis是否能连接：

        Jedis jedis = new Jedis("120.26.yy.xxx",6379);
        System.out.println(jedis.ping());
        log.info("PONG~~"+jedis.ping());

如果ping操作遇到报错：Exception in thread "main" redis.clients.jedis.exceptions.JedisDataException: DENIED Redis is runnin.....

可能只是远程连接redis被拒，我们可以将受保护模式选项设置为“no”，为了让服务器开始从外部接受连接（进入redis的src目录下）

[root@iZbp1hwh629hd4xz80i1z0Z ~]# cd /usr/local/bin
[root@iZbp1hwh629hd4xz80i1z0Z bin]# ./redis-cli
127.0.0.1:6379> config set protected-mode "no"
OK
127.0.0.1:6379>

　　【测试简单事务】

      //jedis.flushDB();
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("gender", "female");
        jsonObject.put("name", "ZOE");
        JSONObject json = new JSONObject();
        json.put("gender","male");
        json.put("name","Ellis");
        // 开启事务
        Transaction multi = jedis.multi();
        String result = jsonObject.toJSONString();
        String resultMirror = json.toJSONString();
        // jedis.watch(result)
        try {
            multi.set("user1", result);
            multi.set("user2", resultMirror);
            // 执行事务
            multi.exec();
        }catch (Exception e){
            // 放弃事务
            multi.discard();
        } finally {
            // 关闭连接
            System.out.println(jedis.get("user1"));
            System.out.println(jedis.get("user2"));
            jedis.close();
        }

输出结果：

{"gender":"female","name":"ZOE"}
{"gender":"male","name":"Ellis"}

Springboot集成Redis

　　springboot2.x后，原来使用的 Jedis 被 lettuce （[ˈletɪs]）替换（2.x内很多redis配置的相关类jedis的资源都默认不存在，所以推荐使用lettuce）。

　　引入依赖：以及springboot相关依赖（略）

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <!-- https://mvnrepository.com/artifact/io.lettuce/lettuce-core -->
        <dependency>
            <groupId>io.lettuce</groupId>
            <artifactId>lettuce-core</artifactId>
            <version>6.0.2.RELEASE</version>
        </dependency>

　　观察一下spring的自动配置特性：

　　位置如下：

　　请看 RedisAutoConfiguration 类，里面有两个默认的模板方法，我们可以自行重写覆盖的，方法名如下

RedisTemplate
StringRedisTemplate

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.boot.autoconfigure.data.redis;

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnClass({RedisOperations.class})
@EnableConfigurationProperties({RedisProperties.class})
@Import({LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class})
public class RedisAutoConfiguration {
    public RedisAutoConfiguration() {
    }

    @Bean
    @ConditionalOnMissingBean(
        name = {"redisTemplate"}
    )
    @ConditionalOnSingleCandidate(RedisConnectionFactory.class)
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<Object, Object> template = new RedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

    @Bean
    @ConditionalOnMissingBean
    @ConditionalOnSingleCandidate(RedisConnectionFactory.class)
    public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory redisConnectionFactory) {
        StringRedisTemplate template = new StringRedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }
}

测试代码：

@SpringBootTest
class RedisBootApplicationTests {

    @Autowired
    private RedisTemplate redisTemplate;

    @Test
    void contextLoads() {
        // redisTemplate 操作不同的数据类型，api和我们的指令是一样的
        // opsForValue 操作字符串 类似String
        // opsForList 操作List 类似List
        // opsForHah

        // 除了基本的操作，我们常用的方法都可以直接通过redisTemplate操作，比如事务和基本的CRUD

        // 获取连接对象
/*        RedisConnection connection = redisTemplate.getConnectionFactory().getConnection();
        connection.flushDb();
        connection.flushAll();*/
        //字符串类型的k-v
        redisTemplate.opsForValue().set("mylove","eggplant");
        System.out.println(redisTemplate.opsForValue().get("mylove"));

    }

}

但是我去用redis终端打开时发现木有这个key：

百度后发现原因：因为Template中set值时会先调用序列化器将键和值都序列化为byte字节数组放入redis数据库中，在客户端除非get后的key为“mylove”使用同样的序列化器序列化后的值，否则取不到值。

解决办法有两个：

　　方法一：在set操作前声明序列化类型

        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new StringRedisSerializer());

　　方法二：声明模板变量时指定泛型

    @Autowired
    private RedisTemplate<String,String> redisTemplate;

另外，如果value是中文的话，序列化后redis终端查询时会显示奇怪的乱码：

　　解决办法：启动cli时多加一个参数就行了，redis-cli --raw这种方式

如果存储对象的话建议把实体类对象转化为json传，代码如下：

　　redisConfig：模板配置类：

package com.wang.demo.utils;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
@Configuration
public class redisConfig {
    @Bean
    @SuppressWarnings("all")
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
        // 我们为了自己开发方便，一般直接使用 <String, Object>
        RedisTemplate<String, Object> template = new RedisTemplate<String,Object>();
        template.setConnectionFactory(factory);
        // Json序列化配置
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(om);
        // String 的序列化
        StringRedisSerializer stringRedisSerializer = new  StringRedisSerializer();
        // key采用String的序列化方式
        template.setKeySerializer(stringRedisSerializer);
        // hash的key也采用String的序列化方式
        template.setHashKeySerializer(stringRedisSerializer);
        // value序列化方式采用jackson
        template.setValueSerializer(jackson2JsonRedisSerializer);
        // hash的value序列化方式采用jackson
        template.setHashValueSerializer(jackson2JsonRedisSerializer);
        template.afterPropertiesSet();
        return template;
    }
}

　　测试类：

    @Test
    public void test()throws JsonProcessingException {
        User user = new User("克里斯",8);
        ObjectMapper mapper = new ObjectMapper();
        //调用writeValueAsString，将指定的对象转换成json
        String jsonUser = mapper.writeValueAsString(user);
        System.out.println("jsonUser"+jsonUser);
        redisTemplate.opsForValue().set("user",jsonUser);
        redisTemplate.opsForValue().set("bookName","雪中悍刀行");

        System.out.println(redisTemplate.opsForValue().get("bookName"));
        System.out.println(redisTemplate.opsForValue().get("user"));
    }

　　注意User要写个对应的构造方法，不然小心value获取不到

redis 配置文件

　　如果找不到配置文件位置，可以在根目录下使用whereis 文件名指令

　输入vim xxx进入vim，输入a进入vim中文本编辑，按esc退出编辑，继续输入 :wq 可以退出vim回到控制台。

　　PS： redis配置文件中大小写不敏感，注意 gb和g是不一样的，类似于 1k是1000,1kb是2的10次方byte=1024 byte

　　其中比较重要的一部分配置参数如下：

# Redis configuration file example.

#
#
bind 127.0.0.1 #绑定ip

protected-mode yes

# Accept connections on the specified port, default is 6379 (IANA #815344).
# If port 0 is specified Redis will not listen on a TCP socket.
port 6379

# TCP listen() backlog.
#
# In high requests-per-second environments you need an high backlog in order
# to avoid slow clients connections issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
tcp-backlog 511

# Unix socket.
#
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /tmp/redis.sock
# unixsocketperm 700

# Close the connection after a client is idle for N seconds (0 to disable)
timeout 0

# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 300 seconds, which is the new
# Redis default starting with Redis 3.2.1.
tcp-keepalive 300

################################# GENERAL #####################################

# By default Redis does not run as a daemon. Use 'yes' if you need it.
# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
daemonize yes

# If you run Redis from upstart or systemd, Redis can interact with your
# supervision tree. Options:
#   supervised no      - no supervision interaction
#   supervised upstart - signal upstart by putting Redis into SIGSTOP mode
#   supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET
#   supervised auto    - detect upstart or systemd method based on
#                        UPSTART_JOB or NOTIFY_SOCKET environment variables
# Note: these supervision methods only signal "process is ready."
#       They do not enable continuous liveness pings back to your supervisor.
supervised no

# If a pid file is specified, Redis writes it where specified at startup
# and removes it at exit.
#
# When the server runs non daemonized, no pid file is created if none is
# specified in the configuration. When the server is daemonized, the pid file
# is used even if not specified, defaulting to "/var/run/redis.pid".
#
# Creating a pid file is best effort: if Redis is not able to create it
# nothing bad happens, the server will start and run normally.
pidfile /var/run/redis_6379.pid

# Specify the server verbosity level.
# This can be one of:
# debug (a lot of information, useful for development/testing)
# verbose (many rarely useful info, but not a mess like the debug level)
# notice (moderately verbose, what you want in production probably)
# warning (only very important / critical messages are logged)
loglevel notice

# Specify the log file name. Also the empty string can be used to force
# Redis to log on the standard output. Note that if you use standard
# output for logging but daemonize, logs will be sent to /dev/null
logfile ""

# To enable logging to the system logger, just set 'syslog-enabled' to yes,
# and optionally update the other syslog parameters to suit your needs.
# syslog-enabled no

# Specify the syslog identity.
# syslog-ident redis

# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# syslog-facility local0

# Set the number of databases. The default database is DB 0, you can select
# a different one on a per-connection basis using SELECT <dbid> where
# dbid is a number between 0 and 'databases'-1
databases 16

# By default Redis shows an ASCII art logo only when started to log to the
# standard output and if the standard output is a TTY. Basically this means
# that normally a logo is displayed only in interactive sessions.
#
# However it is possible to force the pre-4.0 behavior and always show a
# ASCII art logo in startup logs by setting the following option to yes.
always-show-logo yes

################################ SNAPSHOTTING  ################################
#
# Save the DB on disk:
#
#   save <seconds> <changes>
#
#   Will save the DB if both the given number of seconds and the given
#   number of write operations against the DB occurred.
#
#   In the example below the behaviour will be to save:
#   after 900 sec (15 min) if at least 1 key changed
#   after 300 sec (5 min) if at least 10 keys changed
#   after 60 sec if at least 10000 keys changed
#
#   Note: you can disable saving completely by commenting out all "save" lines.
#
#   It is also possible to remove all the previously configured save
#   points by adding a save directive with a single empty string argument
#   like in the following example:
#
#   save ""

save 900 1
save 300 10
save 60 10000

# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
# disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.
stop-writes-on-bgsave-error yes

# Compress string objects using LZF when dump .rdb databases?
# For default that's set to 'yes' as it's almost always a win.
# If you want to save some CPU in the saving child set it to 'no' but
# the dataset will likely be bigger if you have compressible values or keys.
rdbcompression yes

# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.
rdbchecksum yes

# The filename where to dump the DB
dbfilename dump.rdb

# The working directory.
#
# The DB will be written inside this directory, with the filename specified
# above using the 'dbfilename' configuration directive.
#
# The Append Only File will also be created inside this directory.
#
# Note that you must specify a directory here, not a file name.
dir ./

################################# REPLICATION #################################

# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#
# 1) Redis replication is asynchronous, but you can configure a master to
#    stop accepting writes if it appears to be not connected with at least
#    a given number of slaves.
# 2) Redis slaves are able to perform a partial resynchronization with the
#    master if the replication link is lost for a relatively small amount of
#    time. You may want to configure the replication backlog size (see the next
#    sections of this file) with a sensible value depending on your needs.
# 3) Replication is automatic and does not need user intervention. After a
#    network partition slaves automatically try to reconnect to masters
#    and resynchronize with them.
#
# slaveof <masterip> <masterport>

# If the master is password protected (using the "requirepass" configuration
# directive below) it is possible to tell the slave to authenticate before
# starting the replication synchronization process, otherwise the master will
# refuse the slave request.
#
# masterauth <master-password>

# When a slave loses its connection with the master, or when the replication
# is still in progress, the slave can act in two different ways:
#
# 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
#    still reply to client requests, possibly with out of date data, or the
#    data set may just be empty if this is the first synchronization.
#
# 2) if slave-serve-stale-data is set to 'no' the slave will reply with
#    an error "SYNC with master in progress" to all the kind of commands
#    but to INFO and SLAVEOF.
#
slave-serve-stale-data yes

# You can configure a slave instance to accept writes or not. Writing against
# a slave instance may be useful to store some ephemeral data (because data
# written on a slave will be easily deleted after resync with the master) but
# may also cause problems if clients are writing to it because of a
# misconfiguration.
#
# Since Redis 2.6 by default slaves are read-only.
#
# Note: read only slaves are not designed to be exposed to untrusted clients
# on the internet. It's just a protection layer against misuse of the instance.
# Still a read only slave exports by default all the administrative commands
# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
# security of read only slaves using 'rename-command' to shadow all the
# administrative / dangerous commands.
slave-read-only yes

# Replication SYNC strategy: disk or socket.
#
# -------------------------------------------------------
# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
# -------------------------------------------------------
#
# New slaves and reconnecting slaves that are not able to continue the replication
# process just receiving differences, need to do what is called a "full
# synchronization". An RDB file is transmitted from the master to the slaves.
# The transmission can happen in two different ways:
#
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
#                 file on disk. Later the file is transferred by the parent
#                 process to the slaves incrementally.
# 2) Diskless: The Redis master creates a new process that directly writes the
#              RDB file to slave sockets, without touching the disk at all.
#
# With disk-backed replication, while the RDB file is generated, more slaves
# can be queued and served with the RDB file as soon as the current child producing
# the RDB file finishes its work. With diskless replication instead once
# the transfer starts, new slaves arriving will be queued and a new transfer
# will start when the current one terminates.
#
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple slaves
# will arrive and the transfer can be parallelized.
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better.
repl-diskless-sync no

# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the slaves.
#
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5

# Slaves send PINGs to server in a predefined interval. It's possible to change
# this interval with the repl_ping_slave_period option. The default value is 10
# seconds.
#
# repl-ping-slave-period 10

# The following option sets the replication timeout for:
#
# 1) Bulk transfer I/O during SYNC, from the point of view of slave.
# 2) Master timeout from the point of view of slaves (data, pings).
# 3) Slave timeout from the point of view of masters (REPLCONF ACK pings).
#
# It is important to make sure that this value is greater than the value
# specified for repl-ping-slave-period otherwise a timeout will be detected
# every time there is low traffic between the master and the slave.
#
# repl-timeout 60

# Disable TCP_NODELAY on the slave socket after SYNC?
#
# If you select "yes" Redis will use a smaller number of TCP packets and
# less bandwidth to send data to slaves. But this can add a delay for
# the data to appear on the slave side, up to 40 milliseconds with
# Linux kernels using a default configuration.
#
# If you select "no" the delay for data to appear on the slave side will
# be reduced but more bandwidth will be used for replication.
#
# By default we optimize for low latency, but in very high traffic conditions
# or when the master and slaves are many hops away, turning this to "yes" may
# be a good idea.
repl-disable-tcp-nodelay no

# Set the replication backlog size. The backlog is a buffer that accumulates
# slave data when slaves are disconnected for some time, so that when a slave
# wants to reconnect again, often a full resync is not needed, but a partial
# resync is enough, just passing the portion of data the slave missed while
# disconnected.
#
# The bigger the replication backlog, the longer the time the slave can be
# disconnected and later be able to perform a partial resynchronization.
#
# The backlog is only allocated once there is at least a slave connected.
#
# repl-backlog-size 1mb

# After a master has no longer connected slaves for some time, the backlog
# will be freed. The following option configures the amount of seconds that
# need to elapse, starting from the time the last slave disconnected, for
# the backlog buffer to be freed.
#
# Note that slaves never free the backlog for timeout, since they may be
# promoted to masters later, and should be able to correctly "partially
# resynchronize" with the slaves: hence they should always accumulate backlog.
#
# A value of 0 means to never release the backlog.
#
# repl-backlog-ttl 3600

# The slave priority is an integer number published by Redis in the INFO output.
# It is used by Redis Sentinel in order to select a slave to promote into a
# master if the master is no longer working correctly.
#
# A slave with a low priority number is considered better for promotion, so
# for instance if there are three slaves with priority 10, 100, 25 Sentinel will
# pick the one with priority 10, that is the lowest.
#
# However a special priority of 0 marks the slave as not able to perform the
# role of master, so a slave with priority of 0 will never be selected by
# Redis Sentinel for promotion.
#
# By default the priority is 100.
slave-priority 100

# It is possible for a master to stop accepting writes if there are less than
# N slaves connected, having a lag less or equal than M seconds.
#
# The N slaves need to be in "online" state.
#
# The lag in seconds, that must be <= the specified value, is calculated from
# the last ping received from the slave, that is usually sent every second.
#
# This option does not GUARANTEE that N replicas will accept the write, but
# will limit the window of exposure for lost writes in case not enough slaves
# are available, to the specified number of seconds.
#
# For example to require at least 3 slaves with a lag <= 10 seconds use:
#
# min-slaves-to-write 3
# min-slaves-max-lag 10
#
# Setting one or the other to 0 disables the feature.
#
# By default min-slaves-to-write is set to 0 (feature disabled) and
# min-slaves-max-lag is set to 10.

# A Redis master is able to list the address and port of the attached
# slaves in different ways. For example the "INFO replication" section
# offers this information, which is used, among other tools, by
# Redis Sentinel in order to discover slave instances.
# Another place where this info is available is in the output of the
# "ROLE" command of a master.
#
# The listed IP and address normally reported by a slave is obtained
# in the following way:
#
#   IP: The address is auto detected by checking the peer address
#   of the socket used by the slave to connect with the master.
#
#   Port: The port is communicated by the slave during the replication
#   handshake, and is normally the port that the slave is using to
#   list for connections.
#
# However when port forwarding or Network Address Translation (NAT) is
# used, the slave may be actually reachable via different IP and port
# pairs. The following two options can be used by a slave in order to
# report to its master a specific set of IP and port, so that both INFO
# and ROLE will report those values.
#
# There is no need to use both the options if you need to override just
# the port or the IP address.
#
# slave-announce-ip 5.5.5.5
# slave-announce-port 1234

################################## SECURITY ###################################

# Require clients to issue AUTH <PASSWORD> before processing any other
# commands.  This might be useful in environments in which you do not trust
# others with access to the host running redis-server.
#
# This should stay commented out for backward compatibility and because most
# people do not need auth (e.g. they run their own servers).
#
# Warning: since Redis is pretty fast an outside user can try up to
# 150k passwords per second against a good box. This means that you should
# use a very strong password otherwise it will be very easy to break.
#
# requirepass foobared

# Command renaming.
#
# It is possible to change the name of dangerous commands in a shared
# environment. For instance the CONFIG command may be renamed into something
# hard to guess so that it will still be available for internal-use tools
# but not available for general clients.
#
# Example:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# It is also possible to completely kill a command by renaming it into
# an empty string:
#
# rename-command CONFIG ""
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to slaves may cause problems.

################################### CLIENTS ####################################

# Set the max number of connected clients at the same time. By default
# this limit is set to 10000 clients, however if the Redis server is not
# able to configure the process file limit to allow for the specified limit
# the max number of allowed clients is set to the current file limit
# minus 32 (as Redis reserves a few file descriptors for internal uses).
#
# Once the limit is reached Redis will close all the new connections sending
# an error 'max number of clients reached'.
#
# maxclients 10000

############################## MEMORY MANAGEMENT ################################

# Set a memory usage limit to the specified amount of bytes.
# When the memory limit is reached Redis will try to remove keys
# according to the eviction policy selected (see maxmemory-policy).
#
# If Redis can't remove keys according to the policy, or if the policy is
# set to 'noeviction', Redis will start to reply with errors to commands
# that would use more memory, like SET, LPUSH, and so on, and will continue
# to reply to read-only commands like GET.
#
# This option is usually useful when using Redis as an LRU or LFU cache, or to
# set a hard memory limit for an instance (using the 'noeviction' policy).
#
# WARNING: If you have slaves attached to an instance with maxmemory on,
# the size of the output buffers needed to feed the slaves are subtracted
# from the used memory count, so that network problems / resyncs will
# not trigger a loop where keys are evicted, and in turn the output
# buffer of slaves is full with DELs of keys evicted triggering the deletion
# of more keys, and so forth until the database is completely emptied.
#
# In short... if you have slaves attached it is suggested that you set a lower
# limit for maxmemory so that there is some free RAM on the system for slave
# output buffers (but this is not needed if the policy is 'noeviction').
#
# maxmemory <bytes>

# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select among five behaviors:
#
# volatile-lru -> Evict using approximated LRU among the keys with an expire set.
# allkeys-lru -> Evict any key using approximated LRU.
# volatile-lfu -> Evict using approximated LFU among the keys with an expire set.
# allkeys-lfu -> Evict any key using approximated LFU.
# volatile-random -> Remove a random key among the ones with an expire set.
# allkeys-random -> Remove a random key, any key.
# volatile-ttl -> Remove the key with the nearest expire time (minor TTL)
# noeviction -> Don't evict anything, just return an error on write operations.
#
# LRU means Least Recently Used
# LFU means Least Frequently Used
#
# Both LRU, LFU and volatile-ttl are implemented using approximated
# randomized algorithms.
#
# Note: with any of the above policies, Redis will return an error on write
#       operations, when there are no suitable keys for eviction.
#
#       At the date of writing these commands are: set setnx setex append
#       incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd
#       sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby
#       zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby
#       getset mset msetnx exec sort
#
# The default is:
#
# maxmemory-policy noeviction

# LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can tune it for speed or
# accuracy. For default Redis will check five keys and pick the one that was
# used less recently, you can change the sample size using the following
# configuration directive.
#
# The default of 5 produces good enough results. 10 Approximates very closely
# true LRU but costs more CPU. 3 is faster but not very accurate.
#
# maxmemory-samples 5

############################# LAZY FREEING ####################################

# Redis has two primitives to delete keys. One is called DEL and is a blocking
# deletion of the object. It means that the server stops processing new commands
# in order to reclaim all the memory associated with an object in a synchronous
# way. If the key deleted is associated with a small object, the time needed
# in order to execute the DEL command is very small and comparable to most other
# O(1) or O(log_N) commands in Redis. However if the key is associated with an
# aggregated value containing millions of elements, the server can block for
# a long time (even seconds) in order to complete the operation.
#
# For the above reasons Redis also offers non blocking deletion primitives
# such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and
# FLUSHDB commands, in order to reclaim memory in background. Those commands
# are executed in constant time. Another thread will incrementally free the
# object in the background as fast as possible.
#
# DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled.
# It's up to the design of the application to understand when it is a good
# idea to use one or the other. However the Redis server sometimes has to
# delete keys or flush the whole database as a side effect of other operations.
# Specifically Redis deletes objects independently of a user call in the
# following scenarios:
#
# 1) On eviction, because of the maxmemory and maxmemory policy configurations,
#    in order to make room for new data, without going over the specified
#    memory limit.
# 2) Because of expire: when a key with an associated time to live (see the
#    EXPIRE command) must be deleted from memory.
# 3) Because of a side effect of a command that stores data on a key that may
#    already exist. For example the RENAME command may delete the old key
#    content when it is replaced with another one. Similarly SUNIONSTORE
#    or SORT with STORE option may delete existing keys. The SET command
#    itself removes any old content of the specified key in order to replace
#    it with the specified string.
# 4) During replication, when a slave performs a full resynchronization with
#    its master, the content of the whole database is removed in order to
#    load the RDB file just transfered.
#
# In all the above cases the default is to delete objects in a blocking way,
# like if DEL was called. However you can configure each case specifically
# in order to instead release memory in a non-blocking way like if UNLINK
# was called, using the following configuration directives:

lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
slave-lazy-flush no

############################## APPEND ONLY MODE ###############################

# By default Redis asynchronously dumps the dataset on disk. This mode is
# good enough in many applications, but an issue with the Redis process or
# a power outage may result into a few minutes of writes lost (depending on
# the configured save points).
#
# The Append Only File is an alternative persistence mode that provides
# much better durability. For instance using the default data fsync policy
# (see later in the config file) Redis can lose just one second of writes in a
# dramatic event like a server power outage, or a single write if something
# wrong with the Redis process itself happens, but the operating system is
# still running correctly.
#
# AOF and RDB persistence can be enabled at the same time without problems.
# If the AOF is enabled on startup Redis will load the AOF, that is the file
# with the better durability guarantees.
#
# Please check http://redis.io/topics/persistence for more information.

appendonly no

# The name of the append only file (default: "appendonly.aof")

appendfilename "appendonly.aof"

# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting for more data in the output buffer. Some OS will really flush
# data on disk, some other OS will just try to do it ASAP.
#
# Redis supports three different modes:
#
# no: don't fsync, just let the OS flush the data when it wants. Faster.
# always: fsync after every write to the append only log. Slow, Safest.
# everysec: fsync only one time every second. Compromise.
#
# The default is "everysec", as that's usually the right compromise between
# speed and data safety. It's up to you to understand if you can relax this to
# "no" that will let the operating system flush the output buffer when
# it wants, for better performances (but if you can live with the idea of
# some data loss consider the default persistence mode that's snapshotting),
# or on the contrary, use "always" that's very slow but a bit safer than
# everysec.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use "everysec".

# appendfsync always
appendfsync everysec
# appendfsync no

# When the AOF fsync policy is set to always or everysec, and a background
# saving process (a background save or AOF log background rewriting) is
# performing a lot of I/O against the disk, in some Linux configurations
# Redis may block too long on the fsync() call. Note that there is no fix for
# this currently, as even performing fsync in a different thread will block
# our synchronous write(2) call.
#
# In order to mitigate this problem it's possible to use the following option
# that will prevent fsync() from being called in the main process while a
# BGSAVE or BGREWRITEAOF is in progress.
#
# This means that while another child is saving, the durability of Redis is
# the same as "appendfsync none". In practical terms, this means that it is
# possible to lose up to 30 seconds of log in the worst scenario (with the
# default Linux settings).
#
# If you have latency problems turn this to "yes". Otherwise leave it as
# "no" that is the safest pick from the point of view of durability.

no-appendfsync-on-rewrite no

# Automatic rewrite of the append only file.
# Redis is able to automatically rewrite the log file implicitly calling
# BGREWRITEAOF when the AOF log size grows by the specified percentage.
#
# This is how it works: Redis remembers the size of the AOF file after the
# latest rewrite (if no rewrite has happened since the restart, the size of
# the AOF at startup is used).
#
# This base size is compared to the current size. If the current size is
# bigger than the specified percentage, the rewrite is triggered. Also
# you need to specify a minimal size for the AOF file to be rewritten, this
# is useful to avoid rewriting the AOF file even if the percentage increase
# is reached but it is still pretty small.
#
# Specify a percentage of zero in order to disable the automatic AOF
# rewrite feature.

auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

# An AOF file may be found to be truncated at the end during the Redis
# startup process, when the AOF data gets loaded back into memory.
# This may happen when the system where Redis is running
# crashes, especially when an ext4 filesystem is mounted without the
# data=ordered option (however this can't happen when Redis itself
# crashes or aborts but the operating system still works correctly).
#
# Redis can either exit with an error when this happens, or load as much
# data as possible (the default now) and start if the AOF file is found
# to be truncated at the end. The following option controls this behavior.
#
# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
# the Redis server starts emitting a log to inform the user of the event.
# Otherwise if the option is set to no, the server aborts with an error
# and refuses to start. When the option is set to no, the user requires
# to fix the AOF file using the "redis-check-aof" utility before to restart
# the server.
#
# Note that if the AOF file will be found to be corrupted in the middle
# the server will still exit with an error. This option only applies when
# Redis will try to read more data from the AOF file but not enough bytes
# will be found.
aof-load-truncated yes

# When rewriting the AOF file, Redis is able to use an RDB preamble in the
# AOF file for faster rewrites and recoveries. When this option is turned
# on the rewritten AOF file is composed of two different stanzas:
#
#   [RDB file][AOF tail]
#
# When loading Redis recognizes that the AOF file starts with the "REDIS"
# string and loads the prefixed RDB file, and continues loading the AOF
# tail.
#
# This is currently turned off by default in order to avoid the surprise
# of a format change, but will at some point be used as the default.
aof-use-rdb-preamble no

################################ LUA SCRIPTING  ###############################

# Max execution time of a Lua script in milliseconds.
#
# If the maximum execution time is reached Redis will log that a script is
# still in execution after the maximum allowed time and will start to
# reply to queries with an error.
#
# When a long running script exceeds the maximum execution time only the
# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
# used to stop a script that did not yet called write commands. The second
# is the only way to shut down the server in the case a write command was
# already issued by the script but the user doesn't want to wait for the natural
# termination of the script.
#
# Set it to 0 or a negative value for unlimited execution without warnings.
lua-time-limit 5000

################################ REDIS CLUSTER  ###############################
#
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however
# in order to mark it as "mature" we need to wait for a non trivial percentage
# of users to deploy it in production.
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#
# Normal Redis instances can't be part of a Redis Cluster; only nodes that are
# started as cluster nodes can. In order to start a Redis instance as a
# cluster node enable the cluster support uncommenting the following:
#
# cluster-enabled yes

# Every cluster node has a cluster configuration file. This file is not
# intended to be edited by hand. It is created and updated by Redis nodes.
# Every Redis Cluster node requires a different cluster configuration file.
# Make sure that instances running in the same system do not have
# overlapping cluster configuration file names.
#
# cluster-config-file nodes-6379.conf

# Cluster node timeout is the amount of milliseconds a node must be unreachable
# for it to be considered in failure state.
# Most other internal time limits are multiple of the node timeout.
#
# cluster-node-timeout 15000

# A slave of a failing master will avoid to start a failover if its data
# looks too old.
#
# There is no simple way for a slave to actually have an exact measure of
# its "data age", so the following two checks are performed:
#
# 1) If there are multiple slaves able to failover, they exchange messages
#    in order to try to give an advantage to the slave with the best
#    replication offset (more data from the master processed).
#    Slaves will try to get their rank by offset, and apply to the start
#    of the failover a delay proportional to their rank.
#
# 2) Every single slave computes the time of the last interaction with
#    its master. This can be the last ping or command received (if the master
#    is still in the "connected" state), or the time that elapsed since the
#    disconnection with the master (if the replication link is currently down).
#    If the last interaction is too old, the slave will not try to failover
#    at all.
#
# The point "2" can be tuned by user. Specifically a slave will not perform
# the failover if, since the last interaction with the master, the time
# elapsed is greater than:
#
#   (node-timeout * slave-validity-factor) + repl-ping-slave-period
#
# So for example if node-timeout is 30 seconds, and the slave-validity-factor
# is 10, and assuming a default repl-ping-slave-period of 10 seconds, the
# slave will not try to failover if it was not able to talk with the master
# for longer than 310 seconds.
#
# A large slave-validity-factor may allow slaves with too old data to failover
# a master, while a too small value may prevent the cluster from being able to
# elect a slave at all.
#
# For maximum availability, it is possible to set the slave-validity-factor
# to a value of 0, which means, that slaves will always try to failover the
# master regardless of the last time they interacted with the master.
# (However they'll always try to apply a delay proportional to their
# offset rank).
#
# Zero is the only value able to guarantee that when all the partitions heal
# the cluster will always be able to continue.
#
# cluster-slave-validity-factor 10

# Cluster slaves are able to migrate to orphaned masters, that are masters
# that are left without working slaves. This improves the cluster ability
# to resist to failures as otherwise an orphaned master can't be failed over
# in case of failure if it has no working slaves.
#
# Slaves migrate to orphaned masters only if there are still at least a
# given number of other working slaves for their old master. This number
# is the "migration barrier". A migration barrier of 1 means that a slave
# will migrate only if there is at least 1 other working slave for its master
# and so forth. It usually reflects the number of slaves you want for every
# master in your cluster.
#
# Default is 1 (slaves migrate only if their masters remain with at least
# one slave). To disable migration just set it to a very large value.
# A value of 0 can be set but is useful only for debugging and dangerous
# in production.
#
# cluster-migration-barrier 1

# By default Redis Cluster nodes stop accepting queries if they detect there
# is at least an hash slot uncovered (no available node is serving it).
# This way if the cluster is partially down (for example a range of hash slots
# are no longer covered) all the cluster becomes, eventually, unavailable.
# It automatically returns available as soon as all the slots are covered again.
#
# However sometimes you want the subset of the cluster which is working,
# to continue to accept queries for the part of the key space that is still
# covered. In order to do so, just set the cluster-require-full-coverage
# option to no.
#
# cluster-require-full-coverage yes

# In order to setup your cluster make sure to read the documentation
# available at http://redis.io web site.

########################## CLUSTER DOCKER/NAT support  ########################

# In certain deployments, Redis Cluster nodes address discovery fails, because
# addresses are NAT-ted or because ports are forwarded (the typical case is
# Docker and other containers).
#
# In order to make Redis Cluster working in such environments, a static
# configuration where each node knows its public address is needed. The
# following two options are used for this scope, and are:
#
# * cluster-announce-ip
# * cluster-announce-port
# * cluster-announce-bus-port
#
# Each instruct the node about its address, client port, and cluster message
# bus port. The information is then published in the header of the bus packets
# so that other nodes will be able to correctly map the address of the node
# publishing the information.
#
# If the above options are not used, the normal Redis Cluster auto-detection
# will be used instead.
#
# Note that when remapped, the bus port may not be at the fixed offset of
# clients port + 10000, so you can specify any port and bus-port depending
# on how they get remapped. If the bus-port is not set, a fixed offset of
# 10000 will be used as usually.
#
# Example:
#
# cluster-announce-ip 10.1.1.5
# cluster-announce-port 6379
# cluster-announce-bus-port 6380

################################## SLOW LOG ###################################

# The Redis Slow Log is a system to log queries that exceeded a specified
# execution time. The execution time does not include the I/O operations
# like talking with the client, sending the reply and so forth,
# but just the time needed to actually execute the command (this is the only
# stage of command execution where the thread is blocked and can not serve
# other requests in the meantime).
#
# You can configure the slow log with two parameters: one tells Redis
# what is the execution time, in microseconds, to exceed in order for the
# command to get logged, and the other parameter is the length of the
# slow log. When a new command is logged the oldest one is removed from the
# queue of logged commands.

# The following time is expressed in microseconds, so 1000000 is equivalent
# to one second. Note that a negative number disables the slow log, while
# a value of zero forces the logging of every command.
slowlog-log-slower-than 10000

# There is no limit to this length. Just be aware that it will consume memory.
# You can reclaim memory used by the slow log with SLOWLOG RESET.
slowlog-max-len 128

################################ LATENCY MONITOR ##############################

# The Redis latency monitoring subsystem samples different operations
# at runtime in order to collect data related to possible sources of
# latency of a Redis instance.
#
# Via the LATENCY command this information is available to the user that can
# print graphs and obtain reports.
#
# The system only logs operations that were performed in a time equal or
# greater than the amount of milliseconds specified via the
# latency-monitor-threshold configuration directive. When its value is set
# to zero, the latency monitor is turned off.
#
# By default latency monitoring is disabled since it is mostly not needed
# if you don't have latency issues, and collecting data has a performance
# impact, that while very small, can be measured under big load. Latency
# monitoring can easily be enabled at runtime using the command
# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
latency-monitor-threshold 0

############################# EVENT NOTIFICATION ##############################

# Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at http://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key "foo" stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH __keyspace@0__:foo del
# PUBLISH __keyevent@0__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
#  K     Keyspace events, published with __keyspace@<db>__ prefix.
#  E     Keyevent events, published with __keyevent@<db>__ prefix.
#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
#  $     String commands
#  l     List commands
#  s     Set commands
#  h     Hash commands
#  z     Sorted set commands
#  x     Expired events (events generated every time a key expires)
#  e     Evicted events (events generated when a key is evicted for maxmemory)
#  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
#
#  The "notify-keyspace-events" takes as argument a string that is composed
#  of zero or multiple characters. The empty string means that notifications
#  are disabled.
#
#  Example: to enable list and generic events, from the point of view of the
#           event name, use:
#
#  notify-keyspace-events Elg
#
#  Example 2: to get the stream of the expired keys subscribing to channel
#             name __keyevent@0__:expired use:
#
#  notify-keyspace-events Ex
#
#  By default all notifications are disabled because most users don't need
#  this feature and the feature has some overhead. Note that if you don't
#  specify at least one of K or E, no events will be delivered.
notify-keyspace-events ""

############################### ADVANCED CONFIG ###############################

# Hashes are encoded using a memory efficient data structure when they have a
# small number of entries, and the biggest entry does not exceed a given
# threshold. These thresholds can be configured using the following directives.
hash-max-ziplist-entries 512
hash-max-ziplist-value 64

# Lists are also encoded in a special way to save a lot of space.
# The number of entries allowed per internal list node can be specified
# as a fixed maximum size or a maximum number of elements.
# For a fixed maximum size, use -5 through -1, meaning:
# -5: max size: 64 Kb  <-- not recommended for normal workloads
# -4: max size: 32 Kb  <-- not recommended
# -3: max size: 16 Kb  <-- probably not recommended
# -2: max size: 8 Kb   <-- good
# -1: max size: 4 Kb   <-- good
# Positive numbers mean store up to _exactly_ that number of elements
# per list node.
# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size),
# but if your use case is unique, adjust the settings as necessary.
list-max-ziplist-size -2

# Lists may also be compressed.
# Compress depth is the number of quicklist ziplist nodes from *each* side of
# the list to *exclude* from compression.  The head and tail of the list
# are always uncompressed for fast push/pop operations.  Settings are:
# 0: disable all list compression
# 1: depth 1 means "don't start compressing until after 1 node into the list,
#    going from either the head or tail"
#    So: [head]->node->node->...->node->[tail]
#    [head], [tail] will always be uncompressed; inner nodes will compress.
# 2: [head]->[next]->node->node->...->node->[prev]->[tail]
#    2 here means: don't compress head or head->next or tail->prev or tail,
#    but compress all nodes between them.
# 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail]
# etc.
list-compress-depth 0

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happen to be integers in radix 10 in the range
# of 64 bit signed integers.
# The following configuration setting sets the limit in the size of the
# set in order to use this special memory saving encoding.
set-max-intset-entries 512

# Similarly to hashes and lists, sorted sets are also specially encoded in
# order to save a lot of space. This encoding is only used when the length and
# elements of a sorted set are below the following limits:
zset-max-ziplist-entries 128
zset-max-ziplist-value 64

# HyperLogLog sparse representation bytes limit. The limit includes the
# 16 bytes header. When an HyperLogLog using the sparse representation crosses
# this limit, it is converted into the dense representation.
#
# A value greater than 16000 is totally useless, since at that point the
# dense representation is more memory efficient.
#
# The suggested value is ~ 3000 in order to have the benefits of
# the space efficient encoding without slowing down too much PFADD,
# which is O(N) with the sparse encoding. The value can be raised to
# ~ 10000 when CPU is not a concern, but space is, and the data set is
# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
hll-sparse-max-bytes 3000

# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
# order to help rehashing the main Redis hash table (the one mapping top-level
# keys to values). The hash table implementation Redis uses (see dict.c)
# performs a lazy rehashing: the more operation you run into a hash table
# that is rehashing, the more rehashing "steps" are performed, so if the
# server is idle the rehashing is never complete and some more memory is used
# by the hash table.
#
# The default is to use this millisecond 10 times every second in order to
# actively rehash the main dictionaries, freeing memory when possible.
#
# If unsure:
# use "activerehashing no" if you have hard latency requirements and it is
# not a good thing in your environment that Redis can reply from time to time
# to queries with 2 milliseconds delay.
#
# use "activerehashing yes" if you don't have such hard requirements but
# want to free memory asap when possible.
activerehashing yes

# The client output buffer limits can be used to force disconnection of clients
# that are not reading data from the server fast enough for some reason (a
# common reason is that a Pub/Sub client can't consume messages as fast as the
# publisher can produce them).
#
# The limit can be set differently for the three different classes of clients:
#
# normal -> normal clients including MONITOR clients
# slave  -> slave clients
# pubsub -> clients subscribed to at least one pubsub channel or pattern
#
# The syntax of every client-output-buffer-limit directive is the following:
#
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
#
# A client is immediately disconnected once the hard limit is reached, or if
# the soft limit is reached and remains reached for the specified number of
# seconds (continuously).
# So for instance if the hard limit is 32 megabytes and the soft limit is
# 16 megabytes / 10 seconds, the client will get disconnected immediately
# if the size of the output buffers reach 32 megabytes, but will also get
# disconnected if the client reaches 16 megabytes and continuously overcomes
# the limit for 10 seconds.
#
# By default normal clients are not limited because they don't receive data
# without asking (in a push way), but just after a request, so only
# asynchronous clients may create a scenario where data is requested faster
# than it can read.
#
# Instead there is a default limit for pubsub and slave clients, since
# subscribers and slaves receive data in a push fashion.
#
# Both the hard or the soft limit can be disabled by setting them to zero.
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60

# Redis calls an internal function to perform many background tasks, like
# closing connections of clients in timeout, purging expired keys that are
# never requested, and so forth.
#
# Not all tasks are performed with the same frequency, but Redis checks for
# tasks to perform according to the specified "hz" value.
#
# By default "hz" is set to 10. Raising the value will use more CPU when
# Redis is idle, but at the same time will make Redis more responsive when
# there are many keys expiring at the same time, and timeouts may be
# handled with more precision.
#
# The range is between 1 and 500, however a value over 100 is usually not
# a good idea. Most users should use the default of 10 and raise this up to
# 100 only in environments where very low latency is required.
hz 10

# When a child rewrites the AOF file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
aof-rewrite-incremental-fsync yes

# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good
# idea to start with the default settings and only change them after investigating
# how to improve the performances and how the keys LFU change over time, which
# is possible to inspect via the OBJECT FREQ command.
#
# There are two tunable parameters in the Redis LFU implementation: the
# counter logarithm factor and the counter decay time. It is important to
# understand what the two parameters mean before changing them.
#
# The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis
# uses a probabilistic increment with logarithmic behavior. Given the value
# of the old counter, when a key is accessed, the counter is incremented in
# this way:
#
# 1. A random number R between 0 and 1 is extracted.
# 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1).
# 3. The counter is incremented only if R < P.
#
# The default lfu-log-factor is 10. This is a table of how the frequency
# counter changes with a different number of accesses with different
# logarithmic factors:
#
# +--------+------------+------------+------------+------------+------------+
# | factor | 100 hits   | 1000 hits  | 100K hits  | 1M hits    | 10M hits   |
# +--------+------------+------------+------------+------------+------------+
# | 0      | 104        | 255        | 255        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 1      | 18         | 49         | 255        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 10     | 10         | 18         | 142        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 100    | 8          | 11         | 49         | 143        | 255        |
# +--------+------------+------------+------------+------------+------------+
#
# NOTE: The above table was obtained by running the following commands:
#
#   redis-benchmark -n 1000000 incr foo
#   redis-cli object freq foo
#
# NOTE 2: The counter initial value is 5 in order to give new objects a chance
# to accumulate hits.
#
# The counter decay time is the time, in minutes, that must elapse in order
# for the key counter to be divided by two (or decremented if it has a value
# less <= 10).
#
# The default value for the lfu-decay-time is 1. A Special value of 0 means to
# decay the counter every time it happens to be scanned.
#
# lfu-log-factor 10
# lfu-decay-time 1

########################### ACTIVE DEFRAGMENTATION #######################
#
# WARNING THIS FEATURE IS EXPERIMENTAL. However it was stress tested
# even in production and manually tested by multiple engineers for some
# time.
#
# What is active defragmentation?
# -------------------------------
#
# Active (online) defragmentation allows a Redis server to compact the
# spaces left between small allocations and deallocations of data in memory,
# thus allowing to reclaim back memory.
#
# Fragmentation is a natural process that happens with every allocator (but
# less so with Jemalloc, fortunately) and certain workloads. Normally a server
# restart is needed in order to lower the fragmentation, or at least to flush
# away all the data and create it again. However thanks to this feature
# implemented by Oran Agra for Redis 4.0 this process can happen at runtime
# in an "hot" way, while the server is running.
#
# Basically when the fragmentation is over a certain level (see the
# configuration options below) Redis will start to create new copies of the
# values in contiguous memory regions by exploiting certain specific Jemalloc
# features (in order to understand if an allocation is causing fragmentation
# and to allocate it in a better place), and at the same time, will release the
# old copies of the data. This process, repeated incrementally for all the keys
# will cause the fragmentation to drop back to normal values.
#
# Important things to understand:
#
# 1. This feature is disabled by default, and only works if you compiled Redis
#    to use the copy of Jemalloc we ship with the source code of Redis.
#    This is the default with Linux builds.
#
# 2. You never need to enable this feature if you don't have fragmentation
#    issues.
#
# 3. Once you experience fragmentation, you can enable this feature when
#    needed with the command "CONFIG SET activedefrag yes".
#
# The configuration parameters are able to fine tune the behavior of the
# defragmentation process. If you are not sure about what they mean it is
# a good idea to leave the defaults untouched.

# Enabled active defragmentation
# activedefrag yes

# Minimum amount of fragmentation waste to start active defrag
# active-defrag-ignore-bytes 100mb

# Minimum percentage of fragmentation to start active defrag
# active-defrag-threshold-lower 10

# Maximum percentage of fragmentation at which we use maximum effort
# active-defrag-threshold-upper 100

# Minimal effort for defrag in CPU percentage
# active-defrag-cycle-min 25

# Maximal effort for defrag in CPU percentage
# active-defrag-cycle-max 75

View Code

当修改配置文件后需要重新load一下配置文件，不然会报错：连接请求被拒，举例如下

[root@iZbp1hwh629hd4xz80i1z0Z bin]# redis-cli -p 6379
Could not connect to Redis at 127.0.0.1:6379: Connection refused
Could not connect to Redis at 127.0.0.1:6379: Connection refused
not connected> 
not connected> 
[root@iZbp1hwh629hd4xz80i1z0Z bin]# redis-server /etc/redis/6379.conf
4769:C 16 Dec 16:18:24.321 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4769:C 16 Dec 16:18:24.321 # Redis version=4.0.6, bits=64, commit=00000000, modified=0, pid=4769, just started
4769:C 16 Dec 16:18:24.321 # Configuration loaded
[root@iZbp1hwh629hd4xz80i1z0Z bin]# redis-cli -p 6379

着重说一下security的参数：

127.0.0.1:6379> ping
PONG
127.0.0.1:6379> config get requirepass # 获取redis的密码
1) "requirepass"
2) ""
127.0.0.1:6379> config set requirepass "123456" # 设置redis的密码
OK
127.0.0.1:6379> config get requirepass # 发现所有的命令都没有权限了
(error) NOAUTH Authentication required.
127.0.0.1:6379> ping
(error) NOAUTH Authentication required.
127.0.0.1:6379> auth 123456 # 使用密码进行登录！
OK
127.0.0.1:6379> config get requirepass
1) "requirepass"
2) "123456"

注意，设置密码后每次登录redis后想要操作必须要输入auth yourpassword 才行；

持久化RDB操作

　　RDB：redis datebase，因为redis是内存数据库，不进行持久化的数据会断电丢失

　　在指定的时间间隔内将内存中的数据集快照写入磁盘，也就是行话讲的Snapshot快照，它恢复时是将快照文件直接读到内存里。

　　Redis会单独创建一个子进程来进行持久化，会先将数据写入到一个临时文件中，待持久化过程都结束了，再用这个临时文件替换上次持久化好的文件。整个过程中，主进程是不进行任何IO操作的。这就确保了极高的性能。如果需要进行大规模数据的恢复，且对于数据恢复的完整性不是非常敏感，那RDB方式要比AOF方式更加的高效。RDB的缺点是最后一次持久化后的数据可能丢失。我们默认的就是RDB，一般情况下不需要修改这个配置！

有时候在生产环境我们会将这个文件进行备份！

rdb保存的文件是dump.rdb 都是在我们的配置文件中快照中进行配置的！

触发机制

1、save的规则满足的情况下，会自动触发rdb规则
2、执行 flushall 命令，也会触发我们的rdb规则！
3、退出redis，也会产生 rdb 文件
备份就自动生成一个 dump.rdb

　前面提到过，rdb条件在配置文件中有相关配置，示例如下：

save 30 3
# 如果30s内，如果至少进行了3次 key修改，就进行持久化操作，生成rdb文件

　删除rdb文件：

rm -rf dump.rdb  #删除rdb文件

恢复rdb文件

只需要将rdb文件放在我们redis启动目录就可以，redis启动的时候会自动检查dump.rdb 恢复其中的数据！

优点：

1、适合大规模的数据恢复！
2、对数据的完整性要求不高！
缺点：

1、需要一定的时间间隔进程操作！如果redis因意外宕机了，这个最后一次修改数据就没有的了！
2、创建进程的时候，会占用一定的内容空间！！

AOF——Append Only File

　　简单来说就是以日志的形式将我们的所有命令都记录下来（记录写操作，不记录读操作），恢复的时候就把这个文件全部在执行一遍

　　默认是在关闭的，可以配置文件中修改

appendonly no

# The name of the append only file (default: "appendonly.aof")

appendfilename "appendonly.aof"

　　一般的，rdb持久化就可以满足保存数据的需求，不需要用到aof

redis发布订阅（公众号订阅，微博关注等）

　　Redis 发布订阅(pub/sub)是一种消息通信模式：发送者(pub)发送消息，订阅者(sub)接收消息。

假设频道 channel1 ，以及订阅这个频道的三个客户端 —— client1，2

序号	命令及描述
1	PSUBSCRIBE pattern [pattern ...] 订阅一个或多个符合给定模式的频道。
2	PUBSUB subcommand [argument [argument ...]] 查看订阅与发布系统状态。
3	PUBLISH channel message 将信息发送到指定的频道。
4	PUNSUBSCRIBE [pattern [pattern ...]] 退订所有给定模式的频道。
5	SUBSCRIBE channel [channel ...] 订阅给定的一个或多个频道的信息。
6	UNSUBSCRIBE [channel [channel ...]] 指退订给定的频道。

当有新消息通过 PUBLISH 命令发送给频道 channel1 时，这个消息就会被发送给订阅它的三个客户端：

窗口1,2均为订阅端，订阅频道1： channel1，用窗口3作为发送端：代码如下

窗口1：
127.0.0.1:6379> subscribe channel1 
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "channel1"
3) (integer) 1

窗口2：
127.0.0.1:6379> subscribe channel1 
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "channel1"
3) (integer) 1

窗口3：
127.0.0.1:6379> publish channel1 welcome!
(integer) 2
127.0.0.1:6379> 

窗口3的发送端 发送后的1,2均收到消息
127.0.0.1:6379> subscribe channel1 
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "channel1"
3) (integer) 1
1) "message"
2) "channel1"
3) "welcome!"

PS：redis订阅的缺点是：

如果一个客户端订阅了频道，但自己读取消息的速度却不够快的话，那么不断积压的消息会使redis输出缓冲区的体积变得越来越大，这可能使得redis本身的速度变慢，甚至直接崩溃。
这和数据传输可靠性有关，如果在订阅方断线，那么他将会丢失所有在短线期间发布者发布的消息。

redis 主从复制

　　主从复制，是指将一台Redis服务器的数据，复制到其他的Redis服务器。前者称为主节点（Master/Leader）,后者称为从节点（Slave/Follower），数据的复制是单向的！只能由主节点复制到从节点（主节点以写为主、从节点以读为主）。

默认情况下，每台Redis服务器都是主节点，一个主节点可以有0个或者多个从节点，但每个从节点只能由一个主节点。

　　作用：
　　　　数据冗余：主从复制实现了数据的热备份，是持久化之外的一种数据冗余的方式。
　　　　故障恢复：当主节点故障时，从节点可以暂时替代主节点提供服务（实现紧急故障恢复），是一种服务冗余的方式
　　　　负载均衡：在主从复制的基础上，配合读写分离，由主节点进行写操作，从节点进行读操作，分担服务器的负载；尤其是在多读少写的场景下，通过多个从节点　　　　　　分担负载，提高并发量。
　　　　高可用基石：主从复制还是哨兵和集群能够实施的基础。
　　用集群的原因：
　　　　单台服务器难以负载大量的请求
　　　　单台服务器故障率高，系统崩坏概率大
　　　　单台服务器内存容量有限。

　　主从图对应如下：（master主：以写为主，slave从：以读为主）

环境配置
　　需要模拟多个服务，所以我们需要配置多个文件：

#先查看redis 当前库的基础信息
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0 #可以看到没有从机
master_replid:6e310ed1cfa7504bc8d16ee2fba0b6f1456fabf3
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
127.0.0.1:6379>

由于担心我可怜的学生机服务器能不能撑住，所以测试从机数量设为2：

操作流程大致如下：

[root@iZbp1hwh629hd4xz80i1z0Z etc]# vim redis79.conf
[root@iZbp1hwh629hd4xz80i1z0Z etc]# vim redis80.conf
[root@iZbp1hwh629hd4xz80i1z0Z etc]# vim redis81.conf
[root@iZbp1hwh629hd4xz80i1z0Z etc]# redis-server redis79.conf

[root@iZbp1hwh629hd4xz80i1z0Z ~]# ps -ef|grep redis
root      2676     1  0 13:32 ?        00:00:00 redis-server 127.0.0.1:6381
root      5569  4001  0 13:33 pts/7    00:00:00 grep --color=auto redis
root     25964     1  0 13:30 ?        00:00:00 redis-server 127.0.0.1:6379
root     28305     1  0 13:31 ?        00:00:00 redis-server 127.0.0.1:6380

默认情况下，每台Redis服务器都是主节点，如下：

[root@iZbp1hwh629hd4xz80i1z0Z etc]# redis-cli -p 6379
127.0.0.1:6379> auth 123456
(error) ERR Client sent AUTH, but no password is set
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0
master_replid:707c5916fa326b0e87834068cf4327db20f1a79d
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
127.0.0.1:6379>

现在分配从机就好：

可以理解为从机“认主”，配置80,81为从机，79位主机：

现在在窗口2运行客户端6380：

[root@iZbp1hwh629hd4xz80i1z0Z etc]# redis-cli -p 6380
127.0.0.1:6380> slaveof 127.0.0.1 6379
OK
127.0.0.1:6380> info replication
# Replication
role:slave
master_host:127.0.0.1
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:14
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:be7144093698e5f64b2b5ebf34ebf6f9af4be9e3
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:14
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:14
127.0.0.1:6380>

发现本机已变成从机，同理，配置窗口3：从机6381，配置好后观察主机配置：

127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=127.0.0.1,port=6380,state=online,offset=266,lag=0
slave1:ip=127.0.0.1,port=6381,state=online,offset=266,lag=0
master_replid:be7144093698e5f64b2b5ebf34ebf6f9af4be9e3
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:266
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:266
127.0.0.1:6379>

已经拥有两台从机了！

当然，实际应当用配置文件中的replicaof ip port 来配置主从关系~

验证主机写，从机读 ：

127.0.0.1:6380> keys * #从机读取主机的key
1) "k1"
127.0.0.1:6380> set k2 v2
(error) READONLY You can't write against a read only slave.
127.0.0.1:6380>

验证主机宕机，从机情况：

step1：shutdown 主机服务，查看当前进程：

step2：配置从机81为主机：

127.0.0.1:6381> slaveof no one
OK
127.0.0.1:6381> info replication
# Replication
role:master
connected_slaves:0
master_replid:db65d6dce86c29cd2d54ec8d5621e6aed0bf1ac5
master_replid2:be7144093698e5f64b2b5ebf34ebf6f9af4be9e3
master_repl_offset:976
second_repl_offset:977
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:253
repl_backlog_histlen:724
127.0.0.1:6381>

不过如果主机宕机恢复，从机不重新认主的话依然是光杆司令的

哨兵模式：监控主机是否故障，指认从机变为主机来扛大梁：（有单哨兵和多哨兵模式）

多哨兵模式：

相比较上面主从复制方法：当主服务器宕机后，需要手动把一台从服务器切换为主服务器，这就需要人工干预，费事费力，还会造成一段时间内服务不可用。这不是一种推荐的方式，更多时候，我们优先考虑哨兵模式。

哨兵模式是一种特殊的模式，首先Redis提供了哨兵的命令，哨兵是一个独立的进程，作为进程，它会独立运行。其原理是哨兵通过发送命令，等待Redis服务器响应，从而监控运行的多个Redis实例。

由于云服务器配置问题，目前用单哨兵来学习哨兵模式：

配置哨兵：

sentinel monitor mymaster 127.0.0.1 6379
#数字1表示 ：当一个哨兵主观认为主机断开，就可以客观认为主机故障，然后开始选举新的主机。

启动哨兵：

[root@iZbp1hwh629hd4xz80i1z0Z ~]# redis-sentinel sentinel.conf
14609:X 21 Dec 14:20:33.065 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
14609:X 21 Dec 14:20:33.065 # Redis version=4.0.6, bits=64, commit=00000000, modified=0, pid=14609, just started
14609:X 21 Dec 14:20:33.065 # Configuration loaded
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 4.0.6 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in sentinel mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 26379
 |    `-._   `._    /     _.-'    |     PID: 14609
  `-._    `-._  `-./  _.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |           http://redis.io        
  `-._    `-._`-.__.-'_.-'    _.-'                                   
 |`-._`-._    `-.__.-'    _.-'_.-'|                                  
 |    `-._`-._        _.-'_.-'    |                                  
  `-._    `-._`-.__.-'_.-'    _.-'                                   
      `-._    `-.__.-'    _.-'                                       
          `-._        _.-'                                           
              `-.__.-'                                               

14609:X 21 Dec 14:20:33.151 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
14609:X 21 Dec 14:20:33.182 # Sentinel ID is 1a581b8ad032d3131033abad3fc8e89e81e42c67
14609:X 21 Dec 14:20:33.182 # +monitor master myredis 127.0.0.1 6379 quorum 1　　#监控主机ipxx和 6379，主观票数为1

可以看到其端口号默认为26379，#监控主机ipxx和 6379，主观票数为1

我们中断79主机后，发现哨兵打印信息出现变化：

17526:X 21 Dec 14:26:47.444 # +monitor master myredis 127.0.0.1 6379 quorum 1
17526:X 21 Dec 14:26:47.475 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:26:47.524 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.515 # +sdown master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.515 # +odown master myredis 127.0.0.1 6379 #quorum 1/1
17526:X 21 Dec 14:27:25.515 # +new-epoch 2
17526:X 21 Dec 14:27:25.515 # +try-failover master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.543 # +vote-for-leader 1a581b8ad032d3131033abad3fc8e89e81e42c67 2
17526:X 21 Dec 14:27:25.543 # +elected-leader master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.543 # +failover-state-select-slave master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.617 # +selected-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.617 * +failover-state-send-slaveof-noone slave 127.0.0.1:6381 127.0.0.1 6381 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.709 * +failover-state-wait-promotion slave 127.0.0.1:6381 127.0.0.1 6381 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.942 # +promoted-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.942 # +failover-state-reconf-slaves master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:25.994 * +slave-reconf-sent slave 127.0.0.1:6380 127.0.0.1 6380 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:27.051 * +slave-reconf-inprog slave 127.0.0.1:6380 127.0.0.1 6380 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:27.051 * +slave-reconf-done slave 127.0.0.1:6380 127.0.0.1 6380 @ myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:27.103 # +failover-end master myredis 127.0.0.1 6379
17526:X 21 Dec 14:27:27.103 # +switch-master myredis 127.0.0.1 6379 127.0.0.1 6381
17526:X 21 Dec 14:27:27.103 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ myredis 127.0.0.1 6381
17526:X 21 Dec 14:27:27.103 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ myredis 127.0.0.1 6381
17526:X 21 Dec 14:27:57.178 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ myredis 127.0.0.1 6381

我们看到了：switch-master myredis 127.0.0.1 6379 127.0.0.1 6381这一句，可以猜测6381被选为了新的主机，事实上确实如此：

127.0.0.1:6381> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=10038,lag=1
master_replid:5949eecb506754b4e2fa6491837b82233bfb1921
master_replid2:f37ab726110e0d6dde051c109d7ac603c1a3917b
master_repl_offset:10038
second_repl_offset:462
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:10038

如果这个时候我们把主机79重新启动，会发现哨兵输出如下：

17526:X 21 Dec 14:32:41.861 * +convert-to-slave slave 127.0.0.1:6379 127.0.0.1 6379 @ myredis 127.0.0.1 6381

6379被降为81的从机了，这点其实和主从复制类似，区别只是主从中，主机重连后不会被自动分配为从机。

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原文地址：https://www.cnblogs.com/dabuliu/p/15712726.html