hbase异常:java.io.IOException: Unable to determine ZooKeeper ensemble

项目中用到hbase,有时候可能会报一些异常，比如java.io.IOException: Unable to determine ZooKeeper ensemble 等等，当出现这个问题时，根据个人经验，是由于zookeeper集群地址不可访问导致的，但某某说是项目中用到线程池的问题导致的，咱就看看吧，异常信息如下：

java.io.IOException: Unable to determine ZooKeeper ensemble
    at org.apache.hadoop.hbase.zookeeper.ZKUtil.connect(ZKUtil.java:120)
    at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.<init>(ZooKeeperWatcher.java:165)
    at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.<init>(ZooKeeperWatcher.java:134)
    at org.apache.hadoop.hbase.client.ZooKeeperKeepAliveConnection.<init>(ZooKeeperKeepAliveConnection.java:43)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getKeepAliveZooKeeperWatcher(HConnectionManager.java:1710)
    at org.apache.hadoop.hbase.client.ZooKeeperRegistry.isTableOnlineState(ZooKeeperRegistry.java:100)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.isTableDisabled(HConnectionManager.java:879)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.relocateRegion(HConnectionManager.java:1032)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:1255)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1059)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1016)
    at org.apache.hadoop.hbase.client.HTable.finishSetup(HTable.java:326)
    at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:310)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getTable(HConnectionManager.java:712)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getTable(HConnectionManager.java:694)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getTable(HConnectionManager.java:684)
    .........................
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

查看源码ZooKeeperWatcher类：

  public ZooKeeperWatcher(Configuration conf, String identifier,
      Abortable abortable, boolean canCreateBaseZNode)
  throws IOException, ZooKeeperConnectionException {
    this.conf = conf;
    // Capture a stack trace now.  Will print it out later if problem so we can
    // distingush amongst the myriad ZKWs.
    try {
      throw new Exception("ZKW CONSTRUCTOR STACK TRACE FOR DEBUGGING");
    } catch (Exception e) {
      this.constructorCaller = e;
    }
    this.quorum = ZKConfig.getZKQuorumServersString(conf);
    // Identifier will get the sessionid appended later below down when we
    // handle the syncconnect event.
    this.identifier = identifier;
    this.abortable = abortable;
    setNodeNames(conf);
    this.recoverableZooKeeper = ZKUtil.connect(conf, quorum, this, identifier);
    if (canCreateBaseZNode) {
      createBaseZNodes();
    }
  }

从源码中可得知，zookeeper地址存在问题，然后在看看ZKConfig类的方法：

 public static String getZKQuorumServersString(Properties properties) {
    String clientPort = null;
    List<String> servers = new ArrayList<String>();

    // The clientPort option may come after the server.X hosts, so we need to
    // grab everything and then create the final host:port comma separated list.
    boolean anyValid = false;
    for (Entry<Object,Object> property : properties.entrySet()) {
      String key = property.getKey().toString().trim();
      String value = property.getValue().toString().trim();
      if (key.equals("clientPort")) {
        clientPort = value;
      }
      else if (key.startsWith("server.")) {
        String host = value.substring(0, value.indexOf(':'));
        servers.add(host);
        try {
          //noinspection ResultOfMethodCallIgnored
          InetAddress.getByName(host);
          anyValid = true;
        } catch (UnknownHostException e) {
          LOG.warn(StringUtils.stringifyException(e));
        }
      }
    }

    if (!anyValid) {
      LOG.error("no valid quorum servers found in " + HConstants.ZOOKEEPER_CONFIG_NAME);
      return null;
    }

    if (clientPort == null) {
      LOG.error("no clientPort found in " + HConstants.ZOOKEEPER_CONFIG_NAME);
      return null;
    }

    if (servers.isEmpty()) {
      LOG.fatal("No servers were found in provided ZooKeeper configuration. " +
          "HBase must have a ZooKeeper cluster configured for its " +
          "operation. Ensure that you've configured '" +
          HConstants.ZOOKEEPER_QUORUM + "' properly.");
      return null;
    }

    StringBuilder hostPortBuilder = new StringBuilder();
    for (int i = 0; i < servers.size(); ++i) {
      String host = servers.get(i);
      if (i > 0) {
        hostPortBuilder.append(',');
      }
      hostPortBuilder.append(host);
      hostPortBuilder.append(':');
      hostPortBuilder.append(clientPort);
    }

    return hostPortBuilder.toString();
  }

以上可以明确确定是ZooKeeper对应的地址不可访问导致出现异常。不是啥线程池的问题，跟程序中用到线程池没半毛钱关系..........