[jira] [Commented] (HBASE-14498) Master stuck in infinite loop when all Zookeeper servers are unreachable (and RS may run after losing its znode)

["Sean Busbey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-14498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16769772#comment-16769772 ] 

Sean Busbey commented on HBASE-14498:
-------------------------------------

how do we end up with dataloss? when the master sees the loss of zk node, it takes the HDFS lease out from under the WAL so the RS can't accept any additional writes or do anything that would require persisting a WAL edit.

given the history, I recommend you try running ITBLL on a cluster with the patch in place before commit. if you commit this, please pay attention to the nightly runs that follow so it can be reverted if it causes issues again.

No curator please.

> Master stuck in infinite loop when all Zookeeper servers are unreachable (and RS may run after losing its znode)
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-14498
>                 URL: https://issues.apache.org/jira/browse/HBASE-14498
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 3.0.0, 1.5.0, 2.0.0, 2.2.0
>            Reporter: Y. SREENIVASULU REDDY
>            Assignee: Pankaj Kumar
>            Priority: Blocker
>             Fix For: 3.0.0
>
>         Attachments: HBASE-14498-V2.patch, HBASE-14498-V3.patch, HBASE-14498-V4.patch, HBASE-14498-V5.patch, HBASE-14498-V6.patch, HBASE-14498-V6.patch, HBASE-14498-addendum.patch, HBASE-14498-branch-1.2.patch, HBASE-14498-branch-1.3-V2.patch, HBASE-14498-branch-1.3.patch, HBASE-14498-branch-1.4.patch, HBASE-14498-branch-1.patch, HBASE-14498.007.patch, HBASE-14498.008.patch, HBASE-14498.master.001.patch, HBASE-14498.master.002.patch, HBASE-14498.patch
>
>
> We met a weird scenario in our production environment.
> In a HA cluster,
> > Active Master (HM1) is not able to connect to any Zookeeper server (due to N/w breakdown on master machine network with Zookeeper servers).
> {code}
> 2015-09-26 15:24:47,508 INFO [HM1-Host:16000.activeMasterManager-SendThread(ZK-Host:2181)] zookeeper.ClientCnxn: Client session timed out, have not heard from server in 33463ms for sessionid 0x104576b8dda0002, closing socket connection and attempting reconnect
> 2015-09-26 15:24:47,877 INFO [HM1-Host:16000.activeMasterManager-SendThread(ZK-Host1:2181)] client.FourLetterWordMain: connecting to ZK-Host1 2181
> 2015-09-26 15:24:48,236 INFO [main-SendThread(ZK-Host1:2181)] client.FourLetterWordMain: connecting to ZK-Host1 2181
> 2015-09-26 15:24:49,879 WARN [HM1-Host:16000.activeMasterManager-SendThread(ZK-Host1:2181)] zookeeper.ClientCnxn: Can not get the principle name from server ZK-Host1
> 2015-09-26 15:24:49,879 INFO [HM1-Host:16000.activeMasterManager-SendThread(ZK-Host1:2181)] zookeeper.ClientCnxn: Opening socket connection to server ZK-Host1/ZK-IP1:2181. Will not attempt to authenticate using SASL (unknown error)
> 2015-09-26 15:24:50,238 WARN [main-SendThread(ZK-Host1:2181)] zookeeper.ClientCnxn: Can not get the principle name from server ZK-Host1
> 2015-09-26 15:24:50,238 INFO [main-SendThread(ZK-Host1:2181)] zookeeper.ClientCnxn: Opening socket connection to server ZK-Host1/ZK-Host1:2181. Will not attempt to authenticate using SASL (unknown error)
> 2015-09-26 15:25:17,470 INFO [main-SendThread(ZK-Host1:2181)] zookeeper.ClientCnxn: Client session timed out, have not heard from server in 30023ms for sessionid 0x2045762cc710006, closing socket connection and attempting reconnect
> 2015-09-26 15:25:17,571 WARN [master/HM1-Host/HM1-IP:16000] zookeeper.RecoverableZooKeeper: Possibly transient ZooKeeper, quorum=ZK-Host:2181,ZK-Host1:2181,ZK-Host2:2181, exception=org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /hbase/master
> 2015-09-26 15:25:17,872 INFO [main-SendThread(ZK-Host:2181)] client.FourLetterWordMain: connecting to ZK-Host 2181
> 2015-09-26 15:25:19,874 WARN [main-SendThread(ZK-Host:2181)] zookeeper.ClientCnxn: Can not get the principle name from server ZK-Host
> 2015-09-26 15:25:19,874 INFO [main-SendThread(ZK-Host:2181)] zookeeper.ClientCnxn: Opening socket connection to server ZK-Host/ZK-IP:2181. Will not attempt to authenticate using SASL (unknown error)
> {code}
> > Since HM1 was not able to connect to any ZK, so session timeout didnt happen at Zookeeper server side and HM1 didnt abort.
> > On Zookeeper session timeout standby master (HM2) registered himself as an active master. 
> > HM2 is keep on waiting for region server to report him as part of active master intialization.
> {noformat} 
> 2015-09-26 15:24:44,928 | INFO | HM2-Host:21300.activeMasterManager | Waiting for region servers count to settle; currently checked in 0, slept for 0 ms, expecting minimum of 1, maximum of 2147483647, timeout of 4500 ms, interval of 1500 ms. | org.apache.hadoop.hbase.master.ServerManager.waitForRegionServers(ServerManager.java:1011)
> ---
> ---
> 2015-09-26 15:32:50,841 | INFO | HM2-Host:21300.activeMasterManager | Waiting for region servers count to settle; currently checked in 0, slept for 483913 ms, expecting minimum of 1, maximum of 2147483647, timeout of 4500 ms, interval of 1500 ms. | org.apache.hadoop.hbase.master.ServerManager.waitForRegionServers(ServerManager.java:1011)
> {noformat}
> > At other end, region servers are reporting to HM1 on 3 sec interval. Here region server retrieve master location from zookeeper only when they couldn't connect to Master (ServiceException).
> Region Server will not report HM2 as per current design until unless HM1 abort,so HM2 will exit(InitializationMonitor) and again wait for region servers in loop.



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