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  • JedisCluster模式尝试进行批量操作

    搭建完redis集群后,可以通过jedis的JedisCluster来访问Redis集群,这里列出使用jedisCluster的spring bean配置方式:
     
     
    <bean id="jedisPoolConfig" class="redis.clients.jedis.JedisPoolConfig">
            <property name="maxIdle" value="5" />
            <property name="maxTotal" value="1024" />
            <property name="maxWaitMillis" value="5000" />
            <property name="testOnBorrow" value="true" />
        </bean>
    <bean id="redisCluster" class="redis.clients.jedis.JedisCluster"
        <constructor-arg name=“nodes">
            <set>
               <ref bean="hostport1" />
               <ref bean="hostport2" />
               <ref bean="hostport3" />
               <ref bean="hostport4" />
    <ref bean="hostport5" />
    <ref bean="hostport6" />
            </set>
        </constructor-arg>
        <constructor-arg name="timeout" value="6000" />
        <constructor-arg name="poolConfig"
            <ref bean="jedisPoolConfig" />
        </constructor-arg>
    </bean>
     
    //此处省略hostport1....6的配置
     
    本质上,JedisCluster中的JedisPool同样也是实现了apache common pool2的对象池,其中的getResource可以拿到对应的Jedis连接。
     
    JedisCluster是如何构建整个连接池
     
     


     
     
    正如类图中所呈现的,JedisClusterConnectionHandler中使用了JedisClusterInfoCache作为缓存初始化容器,将Set<HostAndPort>作为JedisClusterConnectionHandler的构造函数参数传递过去之后,进行初始化slotsCache操作,
     
     
    public JedisClusterConnectionHandler(Set<HostAndPort> nodes,
        final GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout) {
      this.cache = new JedisClusterInfoCache(poolConfig, connectionTimeout, soTimeout);
      initializeSlotsCache(nodes, poolConfig);
    }
     
    private void initializeSlotsCache(Set<HostAndPort> startNodes, GenericObjectPoolConfig poolConfig) {
      for (HostAndPort hostAndPort : startNodes) {
        Jedis jedis = new Jedis(hostAndPort.getHost(), hostAndPort.getPort());
        try {
          cache.discoverClusterNodesAndSlots(jedis);
          break;
        } catch (JedisConnectionException e) {
          // try next nodes
        } finally {
          if (jedis != null) {
            jedis.close();
          }
        }
      }
     
      for (HostAndPort node : startNodes) {
        cache.setNodeIfNotExist(node);
      }
    }
    
     
     
    在cache.discoverClusterNodesAndSlots中,用到了Jedis.clusterNodes,它可以通过该Redis连接找到其他连接的相关配置,例如可以发现整个集群的配置,其中三个master,三个slave,并且能够识别出自身连接,可参考文档:http://redis.io/commands/cluster-nodes:
     
     
    ./redis-cli -c -h xxx -p 63xx cluster nodes
    e54b82fd2b5ab238906cff7fc6250a7bc66c6fec 192.168.1.1xx:6389 master - 0 1469151811362 31 connected 0-5460
    166baa38c8ab56339c11f0446257c7a6059a219b 192.168.1.1xx:6389 slave 1609b090dfaaac702449b72d30b2330521ce2506 0 1469151812364 29 connected
    1609b090dfaaac702449b72d30b2330521ce2506 192.168.1.1xx:6390 master - 0 1469151811362 29 connected 10923-16383
    539627a393aa43e82ca8c16d1e935611fec4e709 192.168.1.1xx:6388 myself,master - 0 0 28 connected 5461-10922
    d9b3738ff16e99075242b865a0b6cc137c20d502 192.168.1.1xx:6390 slave 539627a393aa43e82ca8c16d1e935611fec4e709 0 1469151810859 28 connected
    101227d3cb13f08a47ad2afe1b348d0efc3cb3b0 192.168.1.1xx:6388 slave e54b82fd2b5ab238906cff7fc6250a7bc66c6fec 0 1469151810357 31 connected
     
     
    命令返回的结果中,可以看到有3个master,3个slave,而且每个slave都有对应的masterid,每个master都有对应的slot范围。
     
    在ClusterNodeInformationParser中,去解析每一行并将对应的slot填充进去,因为只有master上有slot,因此不会填充slave的slot:
     
    public void discoverClusterSlots(Jedis jedis) {
      w.lock();
     
      try {
        this.slots.clear();
     
        List<Object> slots = jedis.clusterSlots();
     
        for (Object slotInfoObj : slots) {
          List<Object> slotInfo = (List<Object>) slotInfoObj;
     
          if (slotInfo.size() <= 2) {
            continue;
          }
     
          List<Integer> slotNums = getAssignedSlotArray(slotInfo);
     
          // hostInfos
          List<Object> hostInfos = (List<Object>) slotInfo.get(2);
          if (hostInfos.size() <= 0) {
            continue;
          }
     
          // at this time, we just use master, discard slave information
          HostAndPort targetNode = generateHostAndPort(hostInfos);
     
          setNodeIfNotExist(targetNode);
          assignSlotsToNode(slotNums, targetNode);
        }
      } finally {
        w.unlock();
      }
    }
     
     
     
    因此,当我们正常地通过访问JedisCluster的get/set时,通过计算key的slot来获取对应的Jedis Connection,根本不会使用到slave,只会访问master节点。只有一种情况,在tryRandomMode开启时(此时,正常通过slot无法获取有效连接时,可能考虑重新排序)。
     
     
    @Override
    public Jedis getConnection() {
      // In antirez's redis-rb-cluster implementation,
      // getRandomConnection always return valid connection (able to
      // ping-pong)
      // or exception if all connections are invalid
     
      List<JedisPool> pools = getShuffledNodesPool();
     
      for (JedisPool pool : pools) {
        Jedis jedis = null;
        try {
          jedis = pool.getResource();
     
          if (jedis == null) {
            continue;
          }
     
          String result = jedis.ping();
     
          if (result.equalsIgnoreCase("pong")) return jedis;
     
          pool.returnBrokenResource(jedis);
        } catch (JedisConnectionException ex) {
          if (jedis != null) {
            pool.returnBrokenResource(jedis);
          }
        }
      }
     
      throw new JedisConnectionException("no reachable node in cluster");
    }
     
     
    但此时拿到一个slave节点的可用Connection是非常危险的,加入当前的操作为写操作,将某个字段写入Redis时,由于master不会从slave节点进行复制,会导致该数据操作没有被持久化至master上。
     
     
    开发基于redis key统一批量处理的中间层
     
     
    根据redis cluster nodes命令来进行,该命令可以识别出当前集群其余节点的所有状态,master/slave,以及检测的slot位置。
     
     
    cluster nodes
    e54b82fd2b5ab238906cff7fc6250a7bc66c6fec 192.168.1.163:6389 master - 0 1469600305090 31 connected 0-5460
    166baa38c8ab56339c11f0446257c7a6059a219b 192.168.1.165:6389 slave 1609b090dfaaac702449b72d30b2330521ce2506 0 1469600304588 29 connected
    1609b090dfaaac702449b72d30b2330521ce2506 192.168.1.163:6390 master - 0 1469600305592 29 connected 10923-16383
    539627a393aa43e82ca8c16d1e935611fec4e709 192.168.1.163:6388 myself,master - 0 0 28 connected 5461-10922
    d9b3738ff16e99075242b865a0b6cc137c20d502 192.168.1.165:6390 slave 539627a393aa43e82ca8c16d1e935611fec4e709 0 1469600305090 28 connected
    101227d3cb13f08a47ad2afe1b348d0efc3cb3b0 192.168.1.165:6388 slave e54b82fd2b5ab238906cff7fc6250a7bc66c6fec 0 1469600304088 31 connected
     
     
    cluster nodes 命令的输出有点儿复杂, 它的每一行都是由以下信息组成的:
     
    • 节点 ID :例如 3fc783611028b1707fd65345e763befb36454d73 。
    • ip:port :节点的 IP 地址和端口号, 例如 127.0.0.1:7000 , 其中 :0 表示的是客户端当前连接的 IP 地址和端口号。
    • flags :节点的角色(例如 master 、 slave 、 myself )以及状态(例如 fail ,等等)。
    • 如果节点是一个从节点的话, 那么跟在 flags 之后的将是主节点的节点 ID : 例如 127.0.0.1:7002 的主节点的节点 ID 就是 3c3a0c74aae0b56170ccb03a76b60cfe7dc1912e 。
    • 集群最近一次向节点发送 PING 命令之后, 过去了多长时间还没接到回复。
    • 节点最近一次返回 PONG 回复的时间。
    • 节点的配置纪元(configuration epoch):详细信息请参考 Redis 集群规范 。
    • 本节点的网络连接情况:例如 connected 。
    • 节点目前包含的槽:例如 127.0.0.1:7001 目前包含号码为 5960 至 10921 的哈希槽。
     
    可以看出redis cluster的slot范围:0-16383,可以采用二分查找的方式,以上面为例,可以分成3个部分的范围slot,以其开头为标识,通过Collections.binarySearch来进行二分查找搜索:
     
     
    0——5460,5461——10922,10923——16383;
     
     
    通过JedisPool/JedisConnection初始化客户端连接,并建立slotStarts,其中的ClusterNodeObject作为描述cluster nodes命令返回的行对象:
     
     
    public void initCluster() {
            if (jedis instanceof BinaryJedisCluster) {
                BinaryJedisCluster jedisCluster = (BinaryJedisCluster) jedis;
     
                Map<String, JedisPool> clusterNodes = jedisCluster.getClusterNodes();
     
                Map<String, ClusterNodeObject> hpToNodeObjectMap = new HashMap<>(clusterNodes.size());
                for (Map.Entry<String, JedisPool> entry : clusterNodes.entrySet()) {
                    JedisPool jedisPool = entry.getValue();
                    Jedis jedis = jedisPool.getResource();
     
                    String clusterNodesCommand = jedis.clusterNodes();
     
                    String[] allNodes = clusterNodesCommand.split("
    ");
                    for (String allNode : allNodes) {
                        String[] splits = allNode.split(" ");
     
                        String hostAndPort = splits[1];
                        ClusterNodeObject clusterNodeObject =
                                new ClusterNodeObject(splits[0], splits[1], splits[2].contains("master"), splits[3],
                                        Long.parseLong(splits[4]), Long.parseLong(splits[5]), splits[6],
                                        splits[7].equalsIgnoreCase("connected"), splits.length == 9 ? splits[8] : null);
     
                        hpToNodeObjectMap.put(hostAndPort, clusterNodeObject);
                    }
                }
                List<Integer> slotStarts = new ArrayList<>();
                for (ClusterNodeObject clusterNodeObject : hpToNodeObjectMap.values()) {
                    if (clusterNodeObject.isConnected() && clusterNodeObject.isMaster()) {
                        String slot = clusterNodeObject.getSlot();
                        String[] slotSplits = slot.split("-");
                        int slotStart = Integer.parseInt(slotSplits[0]);
    //                    int slotEnd = Integer.parseInt(slotSplits[1]);
                        slotStarts.add(slotStart);
                    }
                }
                Collections.sort(slotStarts);
                this.slotStarts = slotStarts;
            }
     
        }
     
     
     
    在拿到各个redis key后,通过getSlotByKey方法,获得对应的node编号:
     
     
    private int getSlotByKey(String key) {
            int slot = JedisClusterCRC16.getSlot(key);
            int slotInsertion = Collections.binarySearch(slotStarts, slot);
            if (slotInsertion < 0) {
                slotInsertion = Math.abs(slotInsertion + 2);
            }
            return slotInsertion;
        }
    
      
     
     
    最后,当批量查询的keys数组>2时,再进行批量出,否则,只进行单独查询。
     
     
    if (keys.length > 2 && jedis instanceof JedisCluster) {
        //如果批量请求key长度大于2,启动批量查询方式
        Map<Integer, List<String>> keySlotsMapList = new HashMap<>();
     
        for (String key : keys) {
            int slotByKey = getSlotByKey(key);
     
            if (!keySlotsMapList.containsKey(slotByKey)) {
                keySlotsMapList.put(slotByKey, new ArrayList<String>());
            }
            keySlotsMapList.get(slotByKey).add(key);
        }
     
        for (Map.Entry<Integer, List<String>> entry : keySlotsMapList.entrySet()) {
            List<String> slotSameKeys = entry.getValue();
            List<String> mgetValues = ((ZhenJedisCluster) jedis)
                    .mget(slotSameKeys.toArray(new String[slotSameKeys.size()]));
     
            for (int i = 0; i < slotSameKeys.size(); i++) {
                result.set(keyList.indexOf(slotSameKeys.get(i)), mgetValues.get(i));
            }
        }
     
    } else {
        for (String key : keys) {
            result.add(jedis.get(key));
        }
    }
     
     
    但不能跳过Jedis客户端的slot key检查,其中的批量操作依赖slot是否相同:
     
     
    public T run(int keyCount, String... keys) {
      if (keys == null || keys.length == 0) {
        throw new JedisClusterException("No way to dispatch this command to Redis Cluster.");
      }
     
      // For multiple keys, only execute if they all share the
      // same connection slot.
      if (keys.length > 1) {
        int slot = JedisClusterCRC16.getSlot(keys[0]);
        for (int i = 1; i < keyCount; i++) {
          int nextSlot = JedisClusterCRC16.getSlot(keys[i]);
          if (slot != nextSlot) {
            throw new JedisClusterException("No way to dispatch this command to Redis Cluster "
                + "because keys have different slots.");
          }
        }
      }
     
      return runWithRetries(SafeEncoder.encode(keys[0]), this.redirections, false, false);
    }
     
     
    虽然可以通过重写JedisCluster以及JedisClusterCommand类型(由于有一些依赖包访问权限的类型,需要将这些重写的类型同样放到redis.clients.jedis包中),跳过了JedisCluster的校验,仍然出现连接错误:
     
    Exception in thread "main" redis.clients.jedis.exceptions.JedisDataException: CROSSSLOT Keys in request don't hash to the same slot
        at redis.clients.jedis.Protocol.processError(Protocol.java:117)
        at redis.clients.jedis.Protocol.process(Protocol.java:151)
        at redis.clients.jedis.Protocol.read(Protocol.java:205)
        at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:297)
        at redis.clients.jedis.Connection.getBinaryMultiBulkReply(Connection.java:233)
        at redis.clients.jedis.Connection.getMultiBulkReply(Connection.java:226)
        at redis.clients.jedis.Jedis.mget(Jedis.java:355)
        at redis.clients.jedis.ZhenJedisCluster$129.execute(ZhenJedisCluster.java:1382)
        at redis.clients.jedis.ZhenJedisCluster$129.execute(ZhenJedisCluster.java:1)
        at redis.clients.jedis.ZhenJedisClusterCommand.runWithRetries(ZhenJedisClusterCommand.java:119)
        at redis.clients.jedis.ZhenJedisClusterCommand.run(ZhenJedisClusterCommand.java:51)
        at redis.clients.jedis.ZhenJedisCluster.mget(ZhenJedisCluster.java:1384)
        at com.api.pub.cache.JedisClient.batchGet(JedisClient.java:525)
        at com.zhen.commons.redis.test.RedisTest.main(RedisTest.java:46)
    
      
     
    可以看出,尽管两个slot在同一个连接上能够get到值,但是在cluster模式下,是通过slot判断而非节点node判断是否可以进行mget操作,不能靠跳过jedis客户端的方案来完成类似分组操作。
     
    我们可以通过命令行操作,同样来验证这一点,注意redis-cli连接时保证在cluster模式下运行,加入-c参数:
     
    redis-cli -c -h 192.168.1.138 -p 6388
    192.168.1.138:6388> set key1 "key1"
    -> Redirected to slot [9189] located at 192.168.1.137:6390
    OK
    192.168.1.137:6390> set key2 "key2"
    -> Redirected to slot [4998] located at 192.168.1.137:6389
    OK
    192.168.1.137:6389> set key3 "key3"
    OK
    192.168.1.137:6389> mget key2 key3
    (error) CROSSSLOT Keys in request don't hash to the same slot
    192.168.1.137:6389> get key2
    "key2"
    192.168.1.137:6389> get key3
    "key3"
    192.168.1.137:6389> get key1
    -> Redirected to slot [9189] located at 192.168.1.137:6390
    "key1"
    192.168.1.137:6390> set {aaa}1 "1"
    OK
    192.168.1.137:6390> set {aaa}2 "2"
    OK
    192.168.1.137:6390> mget {aaa}1 {aaa}2
    1) "1"
    2) "2"
     
     
    因此,暂且不能在RedisCluster模式下,通过增加中间层来对批量请求进行分组,并处理到对应的slot中,理想很好,但是不能够实现,因为服务端会进行一定的限制。
     
    只能通过HASH_TAG来实现cluster模式下的mget/mset批量操作,我们可以在命令行中通过cluster keyslot ${key}来查看某个key对应的slot,可以从Jedis客户端的源码查看对应的key slot算法:
     
     
    public static int getSlot(String key) {
      int s = key.indexOf("{");
      if (s > -1) {
        int e = key.indexOf("}", s + 1);
        if (e > -1 && e != s + 1) {
          key = key.substring(s + 1, e);
        }
      }
      // optimization with modulo operator with power of 2
      // equivalent to getCRC16(key) % 16384
      return getCRC16(key) & (16384 - 1);
    }
     
     
    可以看出,keySlot算法中,如果key包含{},就会使用第一个{}内部的字符串作为hash key,这样就可以保证拥有同样{}内部字符串的key就会拥有相同slot。
     
     
     
     
     
     
     
     
     
     
     
     
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  • 原文地址:https://www.cnblogs.com/mmaa/p/5789848.html
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