Zesheng Wu created HDFS-6827:
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Summary: NameNode double standby
Key: HDFS-6827
URL: https://issues.apache.org/jira/browse/HDFS-6827
Project: Hadoop HDFS
Issue Type: Bug
Components: ha
Affects Versions: 2.4.1
Reporter: Zesheng Wu
Assignee: Zesheng Wu
In our production cluster, we encounter a scenario like this: ANN crashed due
to write journal timeout, and was restarted by the watchdog automatically, but
after restarting both of the NNs are standby.
Following is the logs of the scenario:
# NN1 is down due to write journal timeout:
{color:red}2014-08-03,23:02:02,219{color} INFO
org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG
# ZKFC1 detected "connection reset by peer"
{color:red}2014-08-03,23:02:02,560{color} ERROR
org.apache.hadoop.security.UserGroupInformation: PriviledgedActionException
as:xx@xx.HADOOP (auth:KERBEROS) cause:java.io.IOException:
{color:red}Connection reset by peer{color}
# NN1 wat restarted successfully by the watchdog:
2014-08-03,23:02:07,884 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
Web-server up at: xx:13201
2014-08-03,23:02:07,884 INFO org.apache.hadoop.ipc.Server: IPC Server
Responder: starting
{color:red}2014-08-03,23:02:07,884{color} INFO org.apache.hadoop.ipc.Server:
IPC Server listener on 13200: starting
2014-08-03,23:02:08,742 INFO org.apache.hadoop.ipc.Server: RPC server clean
thread started!
2014-08-03,23:02:08,743 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
Registered DFSClientInformation MBean
2014-08-03,23:02:08,744 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
NameNode up at: xx/xx:13200
2014-08-03,23:02:08,744 INFO
org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Starting services required
for standby state
# ZKFC1 retried the connection and considered NN1 was healthy
{color:red}2014-08-03,23:02:08,292{color} INFO org.apache.hadoop.ipc.Client:
Retrying connect to server: xx/xx:13200. Already tried 0 time(s); retry policy
is RetryUpToMaximumCountWithFixedSleep(maxRetries=1, sleepTime=1 SECONDS)
# ZKFC1 still considered NN1 as a healthy Active NN, and didn't trigger the
failover, as a result, both NNs were standby.
The root cause of this bug is that NN is restarted too quickly and ZKFC health
monitor doesn't realize that.
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