HBase主节点换集群。master节点更换了新的集群，原来的数据没有删除，在启动集群后，master闪挂，请教各位可能的原因是什么？

根据你提供的日志判断master闪挂的原因是有挂掉的DataNode节点，通过节点监控WebUI或者访问各个节点查看是否有DataNode已经挂掉，并且查看hdfs-site.xml文件replication的配置，由于节点坏死导致无法获取Block数据，重启死掉的DataNode节点即可，还有一种原因是DataNode之间的通信有问题，可能性很小，参考以下文章：https://thebipalace.com/2016/05/16/hadoop-error-org-apache-hadoop-hdfs-blockmissingexception-could-not-obtain-block/
HMaster报错是在启动Master的是开启activeMasterManager的时候调用finishActiveMasterInitialization()结束activeMaster初始化的时候this.fileSystemManager = new MasterFileSystem(this, this);由于DataNode节点死掉的缘故，创建MasterFileSystem会抛异常，导致“Failed to become active master”问题，源码如下：
private void startActiveMasterManager(int infoPort) throws KeeperException {

String backupZNode = ZKUtil.joinZNode(
zooKeeper.backupMasterAddressesZNode, serverName.toString());
/*

• Add a ZNode for ourselves in the backup master directory since we
• may not become the active master. If so, we want the actual active
• master to know we are backup masters, so that it won't assign
• regions to us if so configured.
  *
• If we become the active master later, ActiveMasterManager will delete
• this node explicitly. If we crash before then, ZooKeeper will delete
• this node for us since it is ephemeral.
  */

LOG.info("Adding backup master ZNode " + backupZNode);
if (!MasterAddressTracker.setMasterAddress(zooKeeper, backupZNode,

serverName, infoPort)) {

LOG.warn("Failed create of " + backupZNode + " by " + serverName);
}

activeMasterManager.setInfoPort(infoPort);
// Start a thread to try to become the active master, so we won't block here
Threads.setDaemonThreadRunning(new Thread(new Runnable() {
@Override
public void run() {

int timeout = conf.getInt(HConstants.ZK_SESSION_TIMEOUT,
  HConstants.DEFAULT_ZK_SESSION_TIMEOUT);
// If we're a backup master, stall until a primary to writes his address
if (conf.getBoolean(HConstants.MASTER_TYPE_BACKUP,
  HConstants.DEFAULT_MASTER_TYPE_BACKUP)) {
  LOG.debug("HMaster started in backup mode. "
    + "Stalling until master znode is written.");
  // This will only be a minute or so while the cluster starts up,
  // so don't worry about setting watches on the parent znode
  while (!activeMasterManager.hasActiveMaster()) {
    LOG.debug("Waiting for master address ZNode to be written "
      + "(Also watching cluster state node)");
    Threads.sleep(timeout);
  }
}
MonitoredTask status = TaskMonitor.get().createStatus("Master startup");
status.setDescription("Master startup");
try {
  if (activeMasterManager.blockUntilBecomingActiveMaster(timeout, status)) {
    finishActiveMasterInitialization(status);
  }
} catch (Throwable t) {
  status.setStatus("Failed to become active: " + t.getMessage());
  LOG.fatal("Failed to become active master", t);
  // HBASE-5680: Likely hadoop23 vs hadoop 20.x/1.x incompatibility
  if (t instanceof NoClassDefFoundError &&
    t.getMessage()
      .contains("org/apache/hadoop/hdfs/protocol/HdfsConstants$SafeModeAction")) {
    // improved error message for this special case
    abort("HBase is having a problem with its Hadoop jars.  You may need to "
      + "recompile HBase against Hadoop version "
      + org.apache.hadoop.util.VersionInfo.getVersion()
      + " or change your hadoop jars to start properly", t);
  } else {
    abort("Unhandled exception. Starting shutdown.", t);
  }
} finally {
  status.cleanup();
}

}
}, getServerName().toShortString() + ".activeMasterManager"));

}