hadoop mapreduce 写入hbase报错 Session 0x0 for server null, unexpected error, closing socket connection and attempting reconnect

 现象：map任务构造数据正常，reduce任务，开始也正常，速度很快 ，在hbase 的管理界面，可以看到，5W以上的请求数

当reduce 执行到 70% 左右的时候，就堵住了，查看yarn的web界面，可以找到如下报错信息。

不会尝试使用SASL认证。

连接被拒绝。

错误原因，找不到zookeeper 的master。

最开始的时候，配置是这样注入的：

conf.set("hbase.zookeeper.quorum","hostname01,hostname02,hostname03");//ZKFC
conf.set("hbase.master", "ip:port"); 
conf.set("hbase.zookeeper.property.clientPort", "2181");

然后我觉得代码可以精简一下，就变成这样了

conf.set("hbase.zookeeper.quorum","hostname01,hostname02,hostname03");//ZKFC
conf.set("hbase.zookeeper.property.clientPort", "2181");

zookeeper master 不配，也不会报错，可以正常执行，查询使用 “hbase.zookeeper.quorum”“hbase.zookeeper.property.clientPort”，这两个配置就行。

so 

就把“hbase.master”配置去掉了。too young to simple

然后就挂了。。

 报错信息：

2017-12-04 13:23:42,042 INFO [main-SendThread(localhost:2181)] org.apache.zookeeper.ClientCnxn: Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)
2017-12-04 13:23:42,043 WARN [main-SendThread(localhost:2181)] org.apache.zookeeper.ClientCnxn: Session 0x0 for server null, unexpected error, closing socket connection and attempting reconnect
java.net.ConnectException: Connection refused
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
	at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:361)
	at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1081)

2017-12-04 13:23:50,953 ERROR [main] org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper: ZooKeeper exists failed after 4 attempts
2017-12-04 13:23:50,954 WARN [main] org.apache.hadoop.hbase.zookeeper.ZKUtil: hconnection-0x58c34bb30x0, quorum=localhost:2181, baseZNode=/hbase Unable to set watcher on znode (/hbase/hbaseid)
org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /hbase/hbaseid
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:99)
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
	at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1045)
	at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.exists(RecoverableZooKeeper.java:221)
	at org.apache.hadoop.hbase.zookeeper.ZKUtil.checkExists(ZKUtil.java:419)
	at org.apache.hadoop.hbase.zookeeper.ZKClusterId.readClusterIdZNode(ZKClusterId.java:65)
	at org.apache.hadoop.hbase.client.ZooKeeperRegistry.getClusterId(ZooKeeperRegistry.java:105)
	at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.retrieveClusterId(ConnectionManager.java:905)
	at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.<init>(ConnectionManager.java:648)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
	at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:238)
	at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:218)
	at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:119)
	at org.apache.hadoop.hbase.mapreduce.TableOutputFormat$TableRecordWriter.<init>(TableOutputFormat.java:106)
	at org.apache.hadoop.hbase.mapreduce.TableOutputFormat.getRecordWriter(TableOutputFormat.java:153)
	at org.apache.hadoop.mapred.ReduceTask$NewTrackingRecordWriter.<init>(ReduceTask.java:541)
	at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:614)
	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:389)
	at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
	at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)