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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3336) ZK session reconnect still results in loss of ZK lock
Date Wed, 17 Dec 2014 20:27:14 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14250476#comment-14250476
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Josh Elser commented on ACCUMULO-3336:
--------------------------------------

bq.The tablet server that died, is on the same node as where I moved the Accumulo GC process,
but this node is also running a bunch of other Hadoop processes, so I'm not sure if this provides
any useful information. 15 minutes later, the node where the bulk of the Accumulo processes
are running died. 

Ah, that's helpful. It's my hunch that you're just oversubscribing that machine which is causing
you the pain. Check your normal OS-level monitoring: top, free, iostat, etc.

bq. am I right in assuming a tablet server would only run a data node and resource manager
node? Thanks for the help so far!

NodeManager instead of a ResourceManager, but yes. Co-locating datanodes with tabletservers
is good because you can get local reads/writes which avoid a remote RPC. Having a local ResourceManager
will do the same thing (typically in MapReduce jobs, reading local data from the tserver),
however you do have to be careful here to not let the NodeManagers take over that node's resources
too.

> ZK session reconnect still results in loss of ZK lock
> -----------------------------------------------------
>
>                 Key: ACCUMULO-3336
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3336
>             Project: Accumulo
>          Issue Type: Bug
>          Components: zookeeper
>    Affects Versions: 1.5.2, 1.6.1
>            Reporter: Josh Elser
>             Fix For: 1.7.0
>
>
> Saw the following
> {noformat}
> 2014-11-14 08:38:30,612 [zookeeper.DistributedWorkQueue] INFO : Got unexpected zookeeper
event: None for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/bulk_failed_copyq
> 2014-11-14 08:38:30,621 [zookeeper.ZooCache] WARN : Saw (possibly) transient exception
communicating with ZooKeeper, will retry
> org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss
for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/config/tserver.compaction.warn.time
> 	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.accumulo.fate.zookeeper.ZooCache$2.run(ZooCache.java:260)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.retry(ZooCache.java:157)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.get(ZooCache.java:285)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.get(ZooCache.java:232)
> 	at org.apache.accumulo.server.conf.ZooConfiguration.get(ZooConfiguration.java:96)
> 	at org.apache.accumulo.server.conf.ZooConfiguration._get(ZooConfiguration.java:65)
> 	at org.apache.accumulo.server.conf.ZooConfiguration.get(ZooConfiguration.java:90)
> 	at org.apache.accumulo.core.conf.AccumuloConfiguration.getTimeInMillis(AccumuloConfiguration.java:136)
> 	at org.apache.accumulo.tserver.CompactionWatcher.run(CompactionWatcher.java:84)
> 	at org.apache.accumulo.server.util.time.SimpleTimer$LoggingTimerTask.run(SimpleTimer.java:42)
> 	at java.util.TimerThread.mainLoop(Timer.java:555)
> 	at java.util.TimerThread.run(Timer.java:505)
> 2014-11-14 08:38:30,672 [zookeeper.DistributedWorkQueue] INFO : Got unexpected zookeeper
event: None for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/recovery
> 2014-11-14 08:38:30,672 [zookeeper.ZooLock] DEBUG: event null None Disconnected
> 2014-11-14 08:38:31,484 [zookeeper.ZooReader] WARN : Saw (possibly) transient exception
communicating with ZooKeeper
> org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session
expired for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/tservers/ip-172-31-13-177:37709
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
> 	at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1045)
> 	at org.apache.accumulo.fate.zookeeper.ZooReader.getStatus(ZooReader.java:109)
> 	at org.apache.accumulo.fate.zookeeper.ZooLock.process(ZooLock.java:381)
> 	at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:522)
> 	at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:498)
> 2014-11-14 08:38:31,484 [zookeeper.ZooCache] WARN : Saw (possibly) transient exception
communicating with ZooKeeper, will retry
> org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session
expired for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/tables/!0/namespace
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
> 	at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1045)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache$2.run(ZooCache.java:260)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.retry(ZooCache.java:157)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.get(ZooCache.java:285)
> 	at org.apache.accumulo.fate.zookeeper.ZooCache.get(ZooCache.java:232)
> 	at org.apache.accumulo.core.client.impl.Tables.getNamespaceId(Tables.java:304)
> 	at org.apache.accumulo.server.conf.TableParentConfiguration.getNamespaceId(TableParentConfiguration.java:47)
> 	at org.apache.accumulo.server.conf.NamespaceConfiguration.getPath(NamespaceConfiguration.java:85)
> 	at org.apache.accumulo.server.conf.NamespaceConfiguration.get(NamespaceConfiguration.java:98)
> 	at org.apache.accumulo.server.conf.ZooCachePropertyAccessor.get(ZooCachePropertyAccessor.java:107)
> 	at org.apache.accumulo.server.conf.TableConfiguration.get(TableConfiguration.java:103)
> 	at org.apache.accumulo.core.conf.AccumuloConfiguration.getCount(AccumuloConfiguration.java:193)
> 	at org.apache.accumulo.tserver.TabletServer$MajorCompactor.run(TabletServer.java:2636)
> 	at org.apache.accumulo.core.util.LoggingRunnable.run(LoggingRunnable.java:34)
> 	at java.lang.Thread.run(Thread.java:745)
> 2014-11-14 08:38:31,484 [zookeeper.Retry] DEBUG: Sleeping for 250ms before retrying operation
> 2014-11-14 08:38:31,485 [zookeeper.ZooSession] DEBUG: Removing closed ZooKeeper session
to localhost:12644
> 2014-11-14 08:38:31,485 [zookeeper.ZooSession] DEBUG: Connecting to localhost:12644 with
timeout 30000 with auth
> 2014-11-14 08:38:31,588 [zookeeper.ZooSession] DEBUG: Removing closed ZooKeeper session
to localhost:12644
> 2014-11-14 08:38:31,588 [zookeeper.ZooSession] DEBUG: Connecting to localhost:12644 with
timeout 30000 with auth
> 2014-11-14 08:38:31,692 [tserver.TabletServer] DEBUG: gc ParNew=0.10(+0.04) secs ConcurrentMarkSweep=0.05(+0.00)
secs freemem=118,013,904(+6,412,200) totalmem=129,761,280
> 2014-11-14 08:38:31,692 [tserver.TabletServer] WARN : GC pause checker not called in
a timely fashion. Expected every 5.0 seconds but was 43.1 seconds since last check
> 2014-11-14 08:38:31,700 [zookeeper.DistributedWorkQueue] DEBUG: Looking for work in /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/bulk_failed_copyq
> 2014-11-14 08:38:31,701 [zookeeper.DistributedWorkQueue] DEBUG: Looking for work in /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/recovery
> 2014-11-14 08:38:31,715 [tserver.TabletServer] DEBUG: ScanSess tid 172.31.13.177:35935
!0 1 entries in 0.03 secs, nbTimes = [24 24 24.00 1] 
> 2014-11-14 08:38:31,737 [trace.ZooTraceClient] DEBUG: Scanning trace hosts in zookeeper:
/accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/tracers
> 2014-11-14 08:38:31,737 [trace.ZooTraceClient] DEBUG: Trace hosts: []
> 2014-11-14 08:38:31,739 [zookeeper.DistributedWorkQueue] INFO : Got unexpected zookeeper
event: None for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/replication/workqueue
> 2014-11-14 08:38:31,739 [zookeeper.DistributedWorkQueue] INFO : Got unexpected zookeeper
event: None for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/bulk_failed_copyq
> 2014-11-14 08:38:31,739 [zookeeper.DistributedWorkQueue] INFO : Got unexpected zookeeper
event: None for /accumulo/00f38e67-3c29-4cf0-a394-f423a0b33b6b/recovery
> 2014-11-14 08:38:31,739 [zookeeper.ZooSession] DEBUG: Session expired, state of current
session : Expired
> 2014-11-14 08:38:31,739 [zookeeper.ZooLock] DEBUG: event null None Expired
> 2014-11-14 08:38:31,741 [tserver.TabletServer] FATAL: Lost tablet server lock (reason
= SESSION_EXPIRED), exiting.
> {noformat}
> ZooKeeper code appears to had disconnected, closed the disconnected connection and then
opened a new session. However, the ZooLock, IIRC, didn't reconnect and hung the tserver.
> If we want to support this, it might require rehashing some of the ZooLock code (to prevent
the tserver from processing while the tserver doesn't have its lock).



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