[jira] [Commented] (ZOOKEEPER-3814) ZooKeeper caching of config

["Rajkiran Sura (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-3814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17097874#comment-17097874 ] 

Rajkiran Sura commented on ZOOKEEPER-3814:
------------------------------------------

Latest observation, we noticed that ZooKeeper was complaining about dynamic.next file, event though we HAVE NOT ENABLED dynamic-reconfiguration.
{quote}2020-05-02 01:43:05,870 [myid:21] - ERROR [QuorumPeer[myid=21](plain=/0.0.0.0:2181)(secure=disabled):QuorumPeer@1637] - Error writing next dynamic config file to disk:
{quote}
And zookeeper user did not have perms to that config directory, so we fixed that restarted zookeeper. And then it dumped below dynamic.next, which contains the OLD migrated node as a member :O
{quote}$ sudo cat /opt/zookeeper/conf/zoo.cfg.dynamic.next
server.17=node1.foo.bar.com:2888:3888:participant;0.0.0.0:2181
server.19=node2.foo.bar.com:2888:3888:participant;0.0.0.0:2181
server.20=node3.foo.bar.com:2888:3888:participant;0.0.0.0:2181
server.21=node4.foo.bar.com:2888:3888:participant;0.0.0.0:2181
*server.{color:#de350b}22=node5.bar.com{color}*:2888:3888:participant;0.0.0.0:2181
{quote}
So, this looks like a bug. And from where is it still fetching this? How do we fix it.

Any lead/help is very much appreciated.

 

Thanks in advance, 

Rajkiran

> ZooKeeper caching of config
> ---------------------------
>
>                 Key: ZOOKEEPER-3814
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3814
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: leaderElection, quorum, server
>    Affects Versions: 3.5.6
>            Reporter: Rajkiran Sura
>            Priority: Major
>
> Hello,
> We recently upgraded our 5 node ZooKeeper ensemble from v3.4.8 to v3.5.6. Encountered no issues as such.
> This is how the ZooKeeper config looks like:
> {quote}tickTime=2000
> dataDir=/zookeeper-data/
> initLimit=5
> syncLimit=2
> maxClientCnxns=2048
> autopurge.snapRetainCount=3
> autopurge.purgeInterval=1
> 4lw.commands.whitelist=stat, ruok, conf, isro, mntr
> authProvider.1=org.apache.zookeeper.server.auth.SASLAuthenticationProvider
> requireClientAuthScheme=sasl
> quorum.cnxn.threads.size=20
> quorum.auth.enableSasl=true
> quorum.auth.kerberos.servicePrincipal= zookeeper/_HOST
> quorum.auth.learnerRequireSasl=true
> quorum.auth.learner.saslLoginContext=QuorumLearner
> quorum.auth.serverRequireSasl=true
> quorum.auth.server.saslLoginContext=QuorumServer
> server.17=node1.foo.bar.com:2888:3888;2181
> server.19=node2.foo.bar.com:2888:3888;2181
> server.20=node3.foo.bar.com:2888:3888;2181
> server.21=node4.foo.bar.com:2888:3888;2181
> server.22=node5.bar.com:2888:3888;2181
> {quote}
> Post upgrade, we had to migrate server.22 on the same node, but with *FOO*.bar.com domain name due to kerberos referral issues. And, we used different server-identifier, i.e., *23* when we migrated. So, here is how the new config looked like:
> {quote}server.17=node1.foo.bar.com:2888:3888;2181
> server.19=node2.foo.bar.com:2888:3888;2181
> server.20=node3.foo.bar.com:2888:3888;2181
> server.21=node4.foo.bar.com:2888:3888;2181
> *server.23=node5.{color:#00875a}foo{color}.bar.com:2888:3888;2181*
> {quote}
> We restarted all the nodes in the ensemble with the above updated config. And the migrated node joined the quorum successfully and was serving all clients directly connected to it, without any issues.
> Recently, when a leader election happened, server.*23*=node5.foo.bar.com(migrated node) was chosen as Leader (as it has highest ID). But then, ZooKeeper was unable to serve any clients and *all* the servers were _somehow still_ trying to establish a channel to 22 (old DNS name: node5.bar.com) and were throwing below error in a loop:
> {quote}{{2020-05-02 01:43:03,026 [myid:23] - WARN [WorkerSender[myid=23]:QuorumPeer$QuorumServer@196] - Failed to resolve address: node4.bar.com}}
> {{java.net.UnknownHostException: node5.bar.com: Name or service not known}}
> {{ at java.base/java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)}}
> {{ at java.base/java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java:929)}}
> {{ at java.base/java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1515)}}
> {{ at java.base/java.net.InetAddress$NameServiceAddresses.get(InetAddress.java:848)}}
> {{ at java.base/java.net.InetAddress.getAllByName0(InetAddress.java:1505)}}
> {{ at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1364)}}
> {{ at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1298)}}
> {{ at java.base/java.net.InetAddress.getByName(InetAddress.java:1248)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumPeer$QuorumServer.recreateSocketAddresses(QuorumPeer.java:194)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumPeer.recreateSocketAddresses(QuorumPeer.java:774)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:701)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:620)}}
> {{ at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:477)}}
> {{ at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:456)}}
> {{ at java.base/java.lang.Thread.run(Thread.java:834)}}
> {{2020-05-02 01:43:03,026 [myid:23] - WARN [WorkerSender[myid=23]:QuorumCnxManager@679] - Cannot open channel to 22 at election address node5.bar.com:3888}}
> {{java.net.UnknownHostException: node5.bar.com}}
> {{ at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:220)}}
> {{ at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:403)}}
> {{ at java.base/java.net.Socket.connect(Socket.java:591)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:650)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:714)}}
> {{ at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:620)}}
> {{ at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:477)}}
> {{ at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:456)}}
> {{ at java.base/java.lang.Thread.run(Thread.java:834)}}
> {quote}
> Fetching config from live ZooKeeper znode also doesn't show "*22*" being a member of the ensemble. Its not clear how "22" is still coming into the picture.
> {quote}In [4]: zk.get('/zookeeper/config')
> Out[4]:
> ('server.17=node1.foo.bar.com:2888:3888:participant;0.0.0.0:2181\n
> server.19=node2.foo.bar.com:2888:3888:participant;0.0.0.0:2181\n
> server.20=node3.foo.bar.com:2888:3888:participant;0.0.0.0:2181\n
> server.21=node4.foo.bar.com:2888:3888:participant;0.0.0.0:2181\n
> server.23=node5.foo.bar.com:2888:3888:participant;0.0.0.0:2181\n
> version=0',
>  ZnodeStat(czxid=0, mzxid=0, ctime=0, mtime=1588399290245, version=-1, cversion=0, aversion=-1, ephemeralOwner=0, dataLength=360, numChildren=0, pzxid=0))
> {quote}
> We suspected some weird caching issue and restarted ZooKeeper across all the nodes but that didn't help. So, whenever node5 becomes the Leader, ID:22 is popping up. We even rebooted node5 and that hasn't helped too.
> We also looked at '/zookeeper/config' content from snapshot files and did not find any reference to ID:22.
> Any help would be greatly appreciated.
> NOTE: dynamic config is disabled.
> Thanks,
> Rajkiran



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