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https://issues.apache.org/jira/browse/ZOOKEEPER-3814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17102671#comment-17102671
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Rajkiran Sura commented on ZOOKEEPER-3814:
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Hi Mate,
Many thanks for looking further into this.
{quote}If by any chance you still have (and you have the permission to share)
the full server logs from all the servers during the time when you changed the
hostname of the last node, I would be happy to take a look.
{quote}
Unfortunately the logs have rolled back. Also, when we changed the hostname, it
was able to join the cluster without any issues after we did a rolling restart.
And was also serving clients without any issues for a week. Then, when next
leader election happened, it got elected as leader and we had trouble serving
the clients.
{quote}I have a docker environment
([https://github.com/symat/zookeeper-docker-test]) where I tried to create a
cluster and simulating the config change you did.
{quote}
Just checking, if you simulated the removal and addition of server via legacy
rolling-restarts method? Also, we have quorum authn/authz enabled.
FWIW: Even I tried simulating this afresh using a 3-node v3.5.6 cluster. But,
wasn't able to reproduce it exactly.
Also, not sure if this makes any difference but the production cluster was
upgraded from v3.4.8 to v3.5.6. But, for my reproducer/simulation I directly
initialized it with v3.5.6.
> 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
> Assignee: Mate Szalay-Beko
> 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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