第四章阅读 jedis 源码之 JedisCluster 类

JedisCluster 是 jedis 连接 redis 集群操作的一个类，封装了很多操作方法和具体的类，我们先来看 JedisCluster 体系关系图： 

 其实从这里就可以看出整个体系结构根据是否为二进制分为两类。BinaryJedisCluster 实现了集群的二进制操作，而 JedisCluster 直接继承了 BinaryJedisCluster 方法，实现了各种封装类型的方法操作。

下面我们先看下 JedisCluster 构造方法：

  public JedisCluster(HostAndPort node) {
    this(Collections.singleton(node));
  }

  public JedisCluster(HostAndPort node, int timeout) {
    this(Collections.singleton(node), timeout);
  }

  public JedisCluster(HostAndPort node, int timeout, int maxAttempts) {
    this(Collections.singleton(node), timeout, maxAttempts);
  }

  public JedisCluster(HostAndPort node, final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), poolConfig);
  }

  public JedisCluster(HostAndPort node, int timeout, final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), timeout, poolConfig);
  }

  public JedisCluster(HostAndPort node, int timeout, int maxAttempts,
      final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), timeout, maxAttempts, poolConfig);
  }

  public JedisCluster(HostAndPort node, int connectionTimeout, int soTimeout,
      int maxAttempts, final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), connectionTimeout, soTimeout, maxAttempts, poolConfig);
  }

  public JedisCluster(HostAndPort node, int connectionTimeout, int soTimeout,
      int maxAttempts, String password, final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), connectionTimeout, soTimeout, maxAttempts, password, poolConfig);
  }

  public JedisCluster(HostAndPort node, int connectionTimeout, int soTimeout,
      int maxAttempts, String password, String clientName, final GenericObjectPoolConfig poolConfig) {
    this(Collections.singleton(node), connectionTimeout, soTimeout, maxAttempts, password, clientName, poolConfig);
  }

  public JedisCluster(Set nodes) {
    this(nodes, DEFAULT_TIMEOUT);
  }

  public JedisCluster(Set nodes, int timeout) {
    this(nodes, timeout, DEFAULT_MAX_REDIRECTIONS);
  }

  public JedisCluster(Set nodes, int timeout, int maxAttempts) {
    this(nodes, timeout, maxAttempts, new GenericObjectPoolConfig());
  }

  public JedisCluster(Set nodes, final GenericObjectPoolConfig poolConfig) {
    this(nodes, DEFAULT_TIMEOUT, DEFAULT_MAX_REDIRECTIONS, poolConfig);
  }

  public JedisCluster(Set nodes, int timeout, final GenericObjectPoolConfig poolConfig) {
    this(nodes, timeout, DEFAULT_MAX_REDIRECTIONS, poolConfig);
  }

  public JedisCluster(Set jedisClusterNode, int timeout, int maxAttempts,
      final GenericObjectPoolConfig poolConfig) {
    super(jedisClusterNode, timeout, maxAttempts, poolConfig);
  }

  public JedisCluster(Set jedisClusterNode, int connectionTimeout, int soTimeout,
      int maxAttempts, final GenericObjectPoolConfig poolConfig) {
    super(jedisClusterNode, connectionTimeout, soTimeout, maxAttempts, poolConfig);
  }

  public JedisCluster(Set jedisClusterNode, int connectionTimeout, int soTimeout,
                      int maxAttempts, String password, final GenericObjectPoolConfig poolConfig) {
    super(jedisClusterNode, connectionTimeout, soTimeout, maxAttempts, password, poolConfig);
  }

  public JedisCluster(Set jedisClusterNode, int connectionTimeout, int soTimeout,
          int maxAttempts, String password, String clientName, final GenericObjectPoolConfig poolConfig) {
    super(jedisClusterNode, connectionTimeout, soTimeout, maxAttempts, password, clientName, poolConfig);
}

会看到其实也没有什么就是集群信息，然后就直接调用父类的构造方法传递这些信息，下面看下父类  BinaryJedisCluster 的构造方法：

  public static final short HASHSLOTS = 16384;
  protected static final int DEFAULT_TIMEOUT = 2000;
  protected static final int DEFAULT_MAX_REDIRECTIONS = 5;

  protected int maxAttempts;

  protected JedisClusterConnectionHandler connectionHandler;

  public BinaryJedisCluster(Set nodes, int timeout) {
    this(nodes, timeout, DEFAULT_MAX_REDIRECTIONS, new GenericObjectPoolConfig());
  }

  public BinaryJedisCluster(Set nodes) {
    this(nodes, DEFAULT_TIMEOUT);
  }

  public BinaryJedisCluster(Set jedisClusterNode, int timeout, int maxAttempts,
      final GenericObjectPoolConfig poolConfig) {
    this.connectionHandler = new JedisSlotBasedConnectionHandler(jedisClusterNode, poolConfig,
        timeout);
    this.maxAttempts = maxAttempts;
  }

  public BinaryJedisCluster(Set jedisClusterNode, int connectionTimeout,
      int soTimeout, int maxAttempts, final GenericObjectPoolConfig poolConfig) {
    this.connectionHandler = new JedisSlotBasedConnectionHandler(jedisClusterNode, poolConfig,
        connectionTimeout, soTimeout);
    this.maxAttempts = maxAttempts;
  }

  public BinaryJedisCluster(Set jedisClusterNode, int connectionTimeout, int soTimeout, int maxAttempts, String password, GenericObjectPoolConfig poolConfig) {
    this.connectionHandler = new JedisSlotBasedConnectionHandler(jedisClusterNode, poolConfig,
            connectionTimeout, soTimeout, password);
    this.maxAttempts = maxAttempts;
  }

  public BinaryJedisCluster(Set jedisClusterNode, int connectionTimeout, int soTimeout, int maxAttempts, String password, String clientName, GenericObjectPoolConfig poolConfig) {
    this.connectionHandler = new JedisSlotBasedConnectionHandler(jedisClusterNode, poolConfig,
            connectionTimeout, soTimeout, password, clientName);
    this.maxAttempts = maxAttempts;
  }

可以看到连接管理是通过 JedisClusterConnectionHandler 来进行处理，这里看下内部处理：

public class JedisSlotBasedConnectionHandler extends JedisClusterConnectionHandler {

  public JedisSlotBasedConnectionHandler(Set nodes,
      final GenericObjectPoolConfig poolConfig, int timeout) {
    this(nodes, poolConfig, timeout, timeout);
  }

  public JedisSlotBasedConnectionHandler(Set nodes,
      final GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout) {
    super(nodes, poolConfig, connectionTimeout, soTimeout, null);
  }

  public JedisSlotBasedConnectionHandler(Set nodes, GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout, String password) {
    super(nodes, poolConfig, connectionTimeout, soTimeout, password);
  }

  public JedisSlotBasedConnectionHandler(Set nodes, GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout, String password, String clientName) {
    super(nodes, poolConfig, connectionTimeout, soTimeout, password, clientName);
  }

  @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 pools = cache.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;

        jedis.close();
      } catch (JedisException ex) {
        if (jedis != null) {
          jedis.close();
        }
      }
    }

    throw new JedisNoReachableClusterNodeException("No reachable node in cluster");
  }

  @Override
  public Jedis getConnectionFromSlot(int slot) {
    JedisPool connectionPool = cache.getSlotPool(slot);
    if (connectionPool != null) {
      // It can't guaranteed to get valid connection because of node
      // assignment
      return connectionPool.getResource();
    } else {
      renewSlotCache(); //It's abnormal situation for cluster mode, that we have just nothing for slot, try to rediscover state
      connectionPool = cache.getSlotPool(slot);
      if (connectionPool != null) {
        return connectionPool.getResource();
      } else {
        //no choice, fallback to new connection to random node
        return getConnection();
      }
    }
  }
}

接下来看下 JedisCluster 中操作数据的方法，就以 set 为例，其它的方法和这个类似：

  @Override
  public String set(final String key, final String value) {
    return new JedisClusterCommand(connectionHandler, maxAttempts) {
      @Override
      public String execute(Jedis connection) {
        return connection.set(key, value);
      }
    }.run(key);
  }

可以看到直接创建 JedisClusterCommand 实现类调用 run() 方法，执行操作。看下 JedisClusterCommand 类的方法：

public abstract class JedisClusterCommand {

  private final JedisClusterConnectionHandler connectionHandler;
  private final int maxAttempts;
  private final ThreadLocal askConnection = new ThreadLocal();

  public JedisClusterCommand(JedisClusterConnectionHandler connectionHandler, int maxAttempts) {
    this.connectionHandler = connectionHandler;
    this.maxAttempts = maxAttempts;
  }

  public abstract T execute(Jedis connection);

  public T run(String key) {
    if (key == null) {
      throw new JedisClusterException("No way to dispatch this command to Redis Cluster.");
    }

    return runWithRetries(JedisClusterCRC16.getSlot(key), this.maxAttempts, false, false);
  }

  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.
    int slot = JedisClusterCRC16.getSlot(keys[0]);
    if (keys.length > 1) {
      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(slot, this.maxAttempts, false, false);
  }

  public T runBinary(byte[] key) {
    if (key == null) {
      throw new JedisClusterException("No way to dispatch this command to Redis Cluster.");
    }

    return runWithRetries(JedisClusterCRC16.getSlot(key), this.maxAttempts, false, false);
  }

  public T runBinary(int keyCount, byte[]... 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.
    int slot = JedisClusterCRC16.getSlot(keys[0]);
    if (keys.length > 1) {
      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(slot, this.maxAttempts, false, false);
  }

  public T runWithAnyNode() {
    Jedis connection = null;
    try {
      connection = connectionHandler.getConnection();
      return execute(connection);
    } catch (JedisConnectionException e) {
      throw e;
    } finally {
      releaseConnection(connection);
    }
  }

  private T runWithRetries(final int slot, int attempts, boolean tryRandomNode, boolean asking) {
    if (attempts <= 0) {
      throw new JedisClusterMaxRedirectionsException("Too many Cluster redirections?");
    }

    Jedis connection = null;
    try {

      if (asking) {
        // TODO: Pipeline asking with the original command to make it
        // faster....
        connection = askConnection.get();
        connection.asking();

        // if asking success, reset asking flag
        asking = false;
      } else {
        if (tryRandomNode) {
          connection = connectionHandler.getConnection();
        } else {
          connection = connectionHandler.getConnectionFromSlot(slot);
        }
      }

      return execute(connection);

    } catch (JedisNoReachableClusterNodeException jnrcne) {
      throw jnrcne;
    } catch (JedisConnectionException jce) {
      // release current connection before recursion
      releaseConnection(connection);
      connection = null;

      if (attempts <= 1) {
        //We need this because if node is not reachable anymore - we need to finally initiate slots renewing,
        //or we can stuck with cluster state without one node in opposite case.
        //But now if maxAttempts = 1 or 2 we will do it too often. For each time-outed request.
        //TODO make tracking of successful/unsuccessful operations for node - do renewing only
        //if there were no successful responses from this node last few seconds
        this.connectionHandler.renewSlotCache();
      }

      return runWithRetries(slot, attempts - 1, tryRandomNode, asking);
    } catch (JedisRedirectionException jre) {
      // if MOVED redirection occurred,
      if (jre instanceof JedisMovedDataException) {
        // it rebuilds cluster's slot cache
        // recommended by Redis cluster specification
        this.connectionHandler.renewSlotCache(connection);
      }

      // release current connection before recursion or renewing
      releaseConnection(connection);
      connection = null;

      if (jre instanceof JedisAskDataException) {
        asking = true;
        askConnection.set(this.connectionHandler.getConnectionFromNode(jre.getTargetNode()));
      } else if (jre instanceof JedisMovedDataException) {
      } else {
        throw new JedisClusterException(jre);
      }

      return runWithRetries(slot, attempts - 1, false, asking);
    } finally {
      releaseConnection(connection);
    }
  }

  private void releaseConnection(Jedis connection) {
    if (connection != null) {
      connection.close();
    }
  }

}

从上面的执行可以看到，其实这里执行就是先获取到 jedis 后，调用 execut() 方法执行，最终还是使用的 jedis 里面封装的方法执行。