Java连接HBase的正确方法及Connection创建步骤与详解

//所有进程共用一个Connection对象
connection=ConnectionFactory.createConnection(config);
        ...
//每个线程使用单独的Table对象
Table table = connection.getTable(TableName.valueOf("test"));
try {
    ...
} finally {
    table.close();
}

config.set("hbase.client.ipc.pool.type",...);
config.set("hbase.client.ipc.pool.size",...);
connection = ConnectionFactory.createConnection(config);

/**
  * constructor
  * @param conf Configuration object
  */
ConnectionImplementation(Configuration conf,
                    ExecutorService pool, User user) throws IOException {
    ...
    try {
      ...
      this.rpcClient = RpcClientFactory.createClient(this.conf, this.clusterId, this.metrics);
      ...
    } catch (Throwable e) {
      // avoid leaks: registry, rpcClient, ...
      LOG.debug("connection construction failed", e);
      close();
      throw e;
    }
}

protected final PoolMap<ConnectionId, T> connections;

/**
  * Construct an IPC client for the cluster <code>clusterId</code>
  * @param conf configuration
  * @param clusterId the cluster id
  * @param localAddr client socket bind address.
  * @param metrics the connection metrics
  */
public AbstractRpcClient(Configuration conf, String clusterId, SocketAddress localAddr,
      MetricsConnection metrics) {
    ...
    this.connections = new PoolMap<>(getPoolType(conf), getPoolSize(conf));
    ...
}

/**
  * Get a connection from the pool, or create a new one and add it to the pool. Connections to a
  * given host/port are reused.
  */
private T getConnection(ConnectionId remoteId) throws IOException {
    if (failedServers.isFailedServer(remoteId.getAddress())) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Not trying to connect to " + remoteId.address
            + " this server is in the failed servers list");
      }
      throw new FailedServerException(
          "This server is in the failed servers list: " + remoteId.address);
    }
    T conn;
    synchronized (connections) {
      if (!running) {
        throw new StoppedRpcClientException();
      }
      conn = connections.get(remoteId);
      if (conn == null) {
        conn = createConnection(remoteId);
        connections.put(remoteId, conn);
      }
      conn.setLastTouched(EnvironmentEdgeManager.currentTime());
    }
    return conn;
 }

protected NettyRpcConnection createConnection(ConnectionId remoteId) throws IOException {
    return new NettyRpcConnection(this, remoteId);
}

NettyRpcConnection(NettyRpcClient rpcClient, ConnectionId remoteId) throws IOException {
    super(rpcClient.conf, AbstractRpcClient.WHEEL_TIMER, remoteId, rpcClient.clusterId,
        rpcClient.userProvider.isHBaseSecurityEnabled(), rpcClient.codec, rpcClient.compressor);
    this.rpcClient = rpcClient;
    byte connectionHeaderPreamble = getConnectionHeaderPreamble();
    this.connectionHeaderPreamble =
        Unpooled.directBuffer(connectionHeaderPreamble.length).writeBytes(connectionHeaderPreamble);
    ConnectionHeader header = getConnectionHeader();
    this.connectionHeaderWithLength = Unpooled.directBuffer(4 + header.getSerializedSize());
    this.connectionHeaderWithLength.writeInt(header.getSerializedSize());
    header.writeTo(new ByteBufOutputStream(this.connectionHeaderWithLength));
}

protected RpcConnection(Configuration conf, HashedWheelTimer timeoutTimer, ConnectionId remoteId,
      String clusterId, boolean isSecurityEnabled, Codec codec, CompressionCodec compressor)
      throws IOException {
    if (remoteId.getAddress().isUnresolved()) {
      throw new UnknownHostException("unknown host: " + remoteId.getAddress().getHostName());
    }
    this.timeoutTimer = timeoutTimer;
    this.codec = codec;
    this.compressor = compressor;
    this.conf = conf;

    UserGroupInformation ticket = remoteId.getTicket().getUGI();
    SecurityInfo securityInfo = SecurityInfo.getInfo(remoteId.getServiceName());
    this.useSasl = isSecurityEnabled;
    Token<? extends TokenIdentifier> token = null;
    String serverPrincipal = null;
    if (useSasl && securityInfo != null) {
      AuthenticationProtos.TokenIdentifier.Kind tokenKind = securityInfo.getTokenKind();
      if (tokenKind != null) {
        TokenSelector<? extends TokenIdentifier> tokenSelector = AbstractRpcClient.TOKEN_HANDLERS
            .get(tokenKind);
        if (tokenSelector != null) {
          token = tokenSelector.selectToken(new Text(clusterId), ticket.getTokens());
        } else if (LOG.isDebugEnabled()) {
          LOG.debug("No token selector found for type " + tokenKind);
        }
      }
      String serverKey = securityInfo.getServerPrincipal();
      if (serverKey == null) {
        throw new IOException("Can't obtain server Kerberos config key from SecurityInfo");
      }
      serverPrincipal = SecurityUtil.getServerPrincipal(conf.get(serverKey),
        remoteId.address.getAddress().getCanonicalHostName().toLowerCase());
      if (LOG.isDebugEnabled()) {
        LOG.debug("RPC Server Kerberos principal name for service=" + remoteId.getServiceName()
            + " is " + serverPrincipal);
      }
    }
    this.token = token;
    this.serverPrincipal = serverPrincipal;
    if (!useSasl) {
      authMethod = AuthMethod.SIMPLE;
    } else if (token != null) {
      authMethod = AuthMethod.DIGEST;
    } else {
      authMethod = AuthMethod.KERBEROS;
    }

    // Log if debug AND non-default auth, else if trace enabled.
    // No point logging obvious.
    if ((LOG.isDebugEnabled() && !authMethod.equals(AuthMethod.SIMPLE)) ||
        LOG.isTraceEnabled()) {
      // Only log if not default auth.
      LOG.debug("Use " + authMethod + " authentication for service " + remoteId.serviceName
          + ", sasl=" + useSasl);
    }
    reloginMaxBackoff = conf.getInt("hbase.security.relogin.maxbackoff", 5000);
    this.remoteId = remoteId;
}