使用AOF持久化文件实现还原Redis数据库并得到RDB持久化文件

目录

1 编写本文的初衷

2 具体实施

2.1 Redis持久化概念简介

2.2 获取指定Redis的AOF持久化文件

2.3 把Redis的持久化AOF文件转换为RDB文件

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1 编写本文的初衷

因为目前实习工作需求，需要把服务器环境中所有Redis数据进行初步简单分析，即统计其中存储的每一个key所占内存的大小，以便作出清理不重要缓存数据的决策。

 

但是，由于从线上环境获得持久化文件为AOF文件，而不是RDB文件。RDB文件可以通过Rdbtools工具，来分析具体数据。但是AOF文件不能这样操作。

 

因此，就给我带来一个问题：如何通过AOF文件获取指定的RDB持久化文件呢？

 

于是，我通过查阅网上文章，获取的一个解决思路：单独在Redis中开启一个未使用过的端口服务，使用已得到的AOF文件替换该端口服务下自动生成的AOF文件；然后，重启该端口指定的Redis服务，即可把新的AOF文件中数据加载到Redis数据库中，最后在该端口服务客户端执行save或者bgsave命令，即可在指定路径下得到对应的RDB持久化文件。

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2 具体实施

2.1 Redis持久化概念简介

Redis数据库进行持久化有两种方式：RDB持久化和AOF持久化。

 

那么，什么是RDB持久化呢？

RDB(Redis Database)持久化：可以将Redis在内存中的数据库状态保存到磁盘里面，避免数据意外丢失。RDB持久化既可以手动执行，也可以根据服务器配置选项定期执行，该功能可以将某个时间点上的数据库状态保存到一个RDB文件中。（PS：手动执行保存时，在客户端执行SAVE命令或者BGSAVE即可把当前所有数据保存到dump.rdb文件中,如果在线上执行，建议使用BGSAVE命令）

 

RDB文件具体功能：用于保存和还原Redis服务器所有数据库中的所有键值对数据。

 

那么，什么是AOF持久化呢？

AOF(Append Only File)持久化:与RDB持久化通过保存数据库中的键值对来记录数据库状态不同，AOF持久化是通过保存Redis服务器所执行的写命令来记录数据库状态的。AOF持久化功能的实现可以分为命令追加（append）、文件写入、文件同步（sync）三个步骤。

 

AOF文件具体功能：通过保存所有修改数据库的写命令请求来记录服务器的数据库状态。

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2.2 获取指定Redis的AOF持久化文件

一般情况，都是获取限制环境的AOF文件，那么如何在线上环境找到AOF文件呢？（PS：因为时间原因，可能忘记存储在哪里，所以以下提供一个搜索命令，方便操作）

sudo find / -name '*.aof'   # 此命令用于查找系统上所有以aof为后缀的文件 

通过该命令，查看具体文件的路径信息，即可确认自己需要获取的AOF文件。

确定后，通过一下命令把指定AOF文件拷贝到本地主机上：

scp liuzhen@172.160.12.16:/home/liuzhen/prod_redis_data/redis/redis-appendonly.aof . # 从服务器复制远程文件到本地当前所在根目录

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2.3 把Redis的持久化AOF文件转换为RDB文件

关于redis.conf文件中配置aof持久化操作信息简单介绍：

(1)找到redis.conf文件，设置其中的字段属性：

appendonly no ——> appendonly yes

此处也可以在redis客户端，使用指令来完成修改：

redis 127.0.0.1:6379> config set appendonly yes  

OK  

redis 127.0.0.1:6379> BGREWRITEAOF   # 用于重写生成aof文件

Background append only file rewriting started

此选项为aof功能的开关，默认为“no”，可以通过“yes”来开启aof功能  

只有在“yes”下，aof重写/文件同步等特性才会生效  

(2)在redis.conf文件中，指定aof文件的名称

appendfilename "appendonly.aof"  # 这是文件中默认的配置名称，也可以自己修改指定的文件名称

(3)在redis.conf文件中，确认 aof操作中文件同步策略

配置默认结果：

# appendfsync always

appendfsync everysec

# appendfsync no

即选用everysec，具体意思：

1. no:表示等操作系统进行数据缓存同步到磁盘.

2. always:表示每次更新操作后手动调用fsync() 将数据写到磁盘.

3. everysec:表示每秒同步一次.一般用everysec

（4）在redis.conf文件中，确认 aof-rewrite期间，appendfsync是否暂缓文件同步

配置默认结果：

no-appendfsync-on-rewrite no

具体意思：

"no"表示“不暂缓”，“yes”表示“暂缓”，默认为“no”  

（5）在redis.conf文件中，确认 aof文件rewrite触发的最小文件尺寸(mb,gb),以及 相对于“上一次”rewrite，本次rewrite触发时aof文件应该增长的百分比

配置默认结果：

auto-aof-rewrite-percentage 100

auto-aof-rewrite-min-size 64mb

具体实施步骤：

(1) 创建一个新的redis.conf文件，该文件命名可采用redis_port.conf形式，例如：redis_6391.conf。该文件中内容起初完全何Redis默认的redis.conf文件中内容一致

(2) 修改redis_6391.conf指定的port值，在文件中搜索port把默认的6379修改为6391

(3) 修改redis_6391指定的dir值，在文件中搜索dir把默认的"."改为自己要存放文件的具体路径。该路径用于存放RDB文件和AOF文件

(4) 修改redis_6391指定的appendfilename值，在文件中搜索appendfilename把默认的"appendonly.aof"改为自己想要定义的文件名称，该文件即为AOF文件的最终名称

(5) 修改redis_6391指定的dbfilename值，在文件中搜索dbfilename把默认的"dump.rdb"改为自己想要定义的文件名称，该文件即为RDB文件的最终名称

(6) 此步骤最重要，修改redis_6391指定的appendonly值，在文件中搜索appendonly把默认的"no"改为"yes"。这句配置意思是Redis服务重启后，默认不加载AOF持久化文件恢复数据，而是去找RDB持久化文件恢复；如果修改为"yes"后，发现有AOF文件，会首先加载AOF文件恢复数据

以下给出我本机修改后的redis_6391.conf文件中具体配置代码：

# Redis configuration file example

# Note on units: when memory size is needed, it is possible to specify
# it in the usual form of 1k 5GB 4M and so forth:
#
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.

################################## INCLUDES ###################################

# Include one or more other config files here.  This is useful if you
# have a standard template that goes to all Redis server but also need
# to customize a few per-server settings.  Include files can include
# other files, so use this wisely.
#
# Notice option "include" won't be rewritten by command "CONFIG REWRITE"
# from admin or Redis Sentinel. Since Redis always uses the last processed
# line as value of a configuration directive, you'd better put includes
# at the beginning of this file to avoid overwriting config change at runtime.
#
# If instead you are interested in using includes to override configuration
# options, it is better to use include as the last line.
#
# include /path/to/local.conf
# include /path/to/other.conf

################################ 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 no

# When running daemonized, Redis writes a pid file in /var/run/redis.pid by
# default. You can specify a custom pid file location here.
pidfile /var/run/redis.pid

# Accept connections on the specified port, default is 6391.
# If port 0 is specified Redis will not listen on a TCP socket.
port 6391

# 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

# By default Redis listens for connections from all the network interfaces
# available on the server. It is possible to listen to just one or multiple
# interfaces using the "bind" configuration directive, followed by one or
# more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# bind 127.0.0.1

# 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 60 seconds.
tcp-keepalive 0

# 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

################################ 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 at all commenting all the "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_6391.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 /home/liuzhen/data

################################# 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

# 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 biggest 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.
#
# 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 GUARANTEES 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.

################################## 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.

################################### LIMITS ####################################

# 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

# Don't use more memory than 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 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 -> remove the key with an expire set using an LRU algorithm
# allkeys-lru -> remove any key accordingly to the LRU algorithm
# volatile-random -> remove a random key 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 expire at all, just return an error on write operations
# 
# Note: with any of the above policies, Redis will return an error on write
#       operations, when there are not suitable keys for eviction.
#
#       At the date of writing this 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 volatile-lru

# LRU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can select as well the sample
# size to check. For instance for default Redis will check three keys and
# pick the one that was used less recently, you can change the sample size
# using the following configuration directive.
#
# maxmemory-samples 3

############################## 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 yes

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

appendfilename "appendonly_6391.aof"

# The fsync() call tells the Operating System to actually write data on disk
# instead to wait 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

################################ 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 exceed 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 commands was
# already issue by the script but the user don'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

################################## 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 enalbed 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
#  by zero or multiple characters. The empty string means that notifications
#  are disabled at all.
#
#  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

# Similarly to hashes, small lists are also encoded in a special way in order
# to save a lot of space. The special representation is only used when
# you are under the following limits:
list-max-ziplist-entries 512
list-max-ziplist-value 64

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happens 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
# active rehashing 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 form 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 accordingly 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

(7) 重启指定端口的服务，例如此处在Redis按照src目录下，运行./redis-server redis_6391.conf即可启动服务，待服务完成启动成功后，即可把指定的AOF文件数据加载进去（PS：此步骤需要先确认指定目录下的AOF文件已被替换成目标AOF文件，期间可以多次重启实现具体AOF文件加载）

以下给出我本机使用Redis加载启动大小为1.7G的aof文件，由于文件比较大，所以加载的时间有点长，此处是加载了60秒。

liuzhen@liuzhen-ubuntu:~/redis-2.8.17/src$ ./redis-server redis_6391.conf

[68180] 19 Jul 15:02:07.997 * Increased maximum number of open files to 10032 (it was originally set to 1024).

                _._                                                  

           _.-``__ ''-._                                             

      _.-``    `.  `_.  ''-._           Redis 2.8.17 (00000000/0) 64 bit

  .-`` .-```.  ```/    _.,_ ''-._                                   

 (    '      ,       .-`  | `,    )     Running in stand alone mode

 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6391

 |    `-._   `._    /     _.-'    |     PID: 68180

  `-._    `-._  `-./  _.-'    _.-'                                   

 |`-._`-._    `-.__.-'    _.-'_.-'|                                  

 |    `-._`-._        _.-'_.-'    |           http://redis.io        

  `-._    `-._`-.__.-'_.-'    _.-'                                   

 |`-._`-._    `-.__.-'    _.-'_.-'|                                  

 |    `-._`-._        _.-'_.-'    |                                  

  `-._    `-._`-.__.-'_.-'    _.-'                                   

      `-._    `-.__.-'    _.-'                                       

          `-._        _.-'                                           

              `-.__.-'                                               

 

[68180] 19 Jul 15:02:08.011 # Server started, Redis version 2.8.17

[68180] 19 Jul 15:05:12.843 * DB loaded from append only file: 184.831 seconds

[68180] 19 Jul 15:05:12.843 * The server is now ready to accept connections on port 6391

[68180] 19 Jul 15:05:13.008 * 10000 changes in 60 seconds. Saving...

[68180] 19 Jul 15:05:13.084 * Background saving started by pid 68228

[68228] 19 Jul 15:05:47.548 * DB saved on disk

[68228] 19 Jul 15:05:47.613 * RDB: 23 MB of memory used by copy-on-write

[68180] 19 Jul 15:05:47.717 * Background saving terminated with success

[68180] 19 Jul 15:07:54.064 * DB saved on disk

[68180] 19 Jul 15:08:58.096 * Asynchronous AOF fsync is taking too long (disk is busy?). Writing the AOF buffer without waiting for fsync to complete, this may slow down Redis.

[68180] 19 Jul 16:49:14.515 * Background saving started by pid 90980

[90980] 19 Jul 16:56:56.883 * DB saved on disk

[90980] 19 Jul 16:56:56.966 * RDB: 4 MB of memory used by copy-on-write

[68180] 19 Jul 16:56:57.418 * Background saving terminated with success

(8)打开Redis客户端，运行./redis-cli -p 6391,客户端启动成功后，运行命令save，等待命令运行成功后，即可得到本步骤最终目标的RDB持久化文件（PS：此处如果是在线上环境尝试，建议采用bgsave命令）

此处给出，使用AOF文件还原数据后，查看具体数据信息的结果：

liuzhen@liuzhen-ubuntu:~/redis-2.8.17/src$ ./redis-cli -p 6391

127.0.0.1:6391> info

# Server

redis_version:2.8.17

redis_git_sha1:00000000

redis_git_dirty:0

redis_build_id:4ba260b6ab802599

redis_mode:standalone

os:Linux 4.13.0-39-generic x86_64

arch_bits:64

multiplexing_api:epoll

gcc_version:5.4.0

process_id:68180

run_id:97cddc494e3924885bacb03776dfe09e8fa055f9

tcp_port:6391

uptime_in_seconds:9400

uptime_in_days:0

hz:10

lru_clock:5266472

config_file:/home/liuzhen/redis-2.8.17/src/redis_6391.conf

 

# Clients

connected_clients:1

client_longest_output_list:0

client_biggest_input_buf:0

blocked_clients:0

 

# Memory

used_memory:2239514040

used_memory_human:2.09G

used_memory_rss:330895360

used_memory_peak:2272377648

used_memory_peak_human:2.12G

used_memory_lua:38912

mem_fragmentation_ratio:0.15

mem_allocator:jemalloc-3.6.0

 

# Persistence

loading:0

rdb_changes_since_last_save:0

rdb_bgsave_in_progress:0

rdb_last_save_time:1531990617

rdb_last_bgsave_status:ok

rdb_last_bgsave_time_sec:463

rdb_current_bgsave_time_sec:-1

aof_enabled:1

aof_rewrite_in_progress:0

aof_rewrite_scheduled:0

aof_last_rewrite_time_sec:-1

aof_current_rewrite_time_sec:-1

aof_last_bgrewrite_status:ok

aof_last_write_status:ok

aof_current_size:1700508277

aof_base_size:1699947297

aof_pending_rewrite:0

aof_buffer_length:0

aof_rewrite_buffer_length:0

aof_pending_bio_fsync:0

aof_delayed_fsync:1

 

# Stats

total_connections_received:2

total_commands_processed:281

instantaneous_ops_per_sec:0

rejected_connections:0

sync_full:0

sync_partial_ok:0

sync_partial_err:0

expired_keys:9290

evicted_keys:0

keyspace_hits:1065050

keyspace_misses:0

pubsub_channels:0

pubsub_patterns:0

latest_fork_usec:101807

 

# Replication

role:master

connected_slaves:0

master_repl_offset:0

repl_backlog_active:0

repl_backlog_size:1048576

repl_backlog_first_byte_offset:0

repl_backlog_histlen:0

 

# CPU

used_cpu_sys:46.01

used_cpu_user:189.71

used_cpu_sys_children:134.11

used_cpu_user_children:79.12

 

# Keyspace

db1:keys=1146336,expires=51965,avg_ttl=276142509

127.0.0.1:6391>

备注：在Redis指定端口服务加载给定的AOF文件时，如果AOF文件过大，系统可能会报如下错误：

 Can't save in background: fork: Cannot allocate memory

解决办法：

修改系统/etc/sysctl.conf文件，并添加以下内容：

vm.overcommit_memory=1

在 FreeBSD上:

sudo /etc/rc.d/sysctl reload

在 Linux上:

sudo sysctl -p /etc/sysctl.conf

 

---

参考资料：

• 1.redis中的数据快照、AOF、数据恢复、主从复制介绍及使用（https://blog.csdn.net/zhu_xun/article/details/16806697）
• 2.redis如何利用appendonly.aof恢复数据（https://blog.csdn.net/sanbingyutuoniao123/article/details/50484674）
• 3.Redis持久存储(AOF/Snapshot)（http://shift-alt-ctrl.iteye.com/blog/1878716）
• 4.redis dump.rdb appendonly.aof 文件路径修改（https://blog.csdn.net/yangxujia/article/details/51010222）
• 5.超大数据快速导入MySQL（https://blog.csdn.net/dingding_12345/article/details/78646484）
• 6.redis Can’t save in background: fork: Cannot allocate memory 解决及原理（https://blog.csdn.net/zqz_zqz/article/details/53384854）
• 7.redis bgsave failed because fork Cannot allocate memory（https://stackoverflow.com/questions/11752544/redis-bgsave-failed-because-fork-cannot-allocate-memory）
• 8.《Redis设计与实现 第二版》  黄健宏 著