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https://issues.apache.org/jira/browse/ZOOKEEPER-2867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16121935#comment-16121935
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Michael Han commented on ZOOKEEPER-2867:
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bq. That Kafka broker went down around Aug 2, 23:16:11. The expectation is that
its ZK session will be closed and the registered ephemeral node will be removed.
The expectation will be correct if this Kafka broker really died. But if it was
a transient interruption, i.e. network issues between that Kafka broker and
ZooKeeper, then the session will be renewed and ephemeral nodes appertain to
that session will be intact. From the original log posted, the session
{{0x25cd1e82c110001}} was renewed (though the timestamp of the log does not
match {{Aug 2, 23:16:11}} so probably we are not talking about same event. In
any case, do we have any evidence that indicates the broker in question really
died?
bq. the following entry doesn't necessarily mean that the ephemeral node is
actually removed since it could be restored.
Correct, I think this log does not imply the final quorum state W.R.T. the
ephemeral nodes, because the logging here was done before a consensus regarding
the ephemeral removal proposal was reached. When a server thinks a client is
dead and initiates the session closing, it will start removing the ephemerals
from its data tree while waiting for the votes of the ephemeral removal
proposal, so the ephemeral nodes removal here does not have transactional
semantic because it does not consider the proposal results.
bq. Is there any logging indicating the restore?
When log level is set to DEBUG, {{FinalRequestPrecessor}} will log all requests
it processes, including the ephemeral nodes recreate (which is just normal
ephemeral node create since it has no notion of a state). You can probably
search {{type:create}} in logs.
The restore will only happen when a server restarts, or rejoin quorum, and
finds out it has out dated state with rest of quorum. Otherwise, the ephemeral
nodes will either be removed already at quorum level, or not removed at all (on
this specific server) :). In both cases (restarts/rejoin quorum), the server
will recover the expected state from rest of quorum by replaying transactions
logs.
> an expired ZK session can be re-established
> -------------------------------------------
>
> Key: ZOOKEEPER-2867
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2867
> Project: ZooKeeper
> Issue Type: Bug
> Affects Versions: 3.4.10
> Reporter: Jun Rao
> Attachments: zk.0.formatted, zk.1.formatted
>
>
> Not sure if this is a real bug, but I found an instance when a ZK client
> seems to be able to renew a session already expired by the ZK server.
> From ZK server log, session 25cd1e82c110001 was expired at 22:04:39.
> {code:java}
> June 27th 2017, 22:04:39.000 INFO
> org.apache.zookeeper.server.ZooKeeperServer Expiring session
> 0x25cd1e82c110001, timeout of 12000ms exceeded
> June 27th 2017, 22:04:39.001 DEBUG
> org.apache.zookeeper.server.quorum.Leader Proposing::
> sessionid:0x25cd1e82c110001 type:closeSession cxid:0x0 zxid:0x200000fc4
> txntype:-11 reqpath:n/a
> June 27th 2017, 22:04:39.001 INFO
> org.apache.zookeeper.server.PrepRequestProcessor Processed session
> termination for sessionid: 0x25cd1e82c110001
> June 27th 2017, 22:04:39.001 DEBUG
> org.apache.zookeeper.server.quorum.CommitProcessor Processing request::
> sessionid:0x25cd1e82c110001 type:closeSession cxid:0x0 zxid:0x200000fc4
> txntype:-11 reqpath:n/a
> June 27th 2017, 22:05:20.324 INFO
> org.apache.zookeeper.server.quorum.Learner Revalidating client:
> 0x25cd1e82c110001
> June 27th 2017, 22:05:20.324 INFO
> org.apache.zookeeper.server.ZooKeeperServer Client attempting to renew
> session 0x25cd1e82c110001 at /100.96.5.6:47618
> June 27th 2017, 22:05:20.325 INFO
> org.apache.zookeeper.server.ZooKeeperServer Established session
> 0x25cd1e82c110001 with negotiated timeout 12000 for client /100.96.5.6:47618
> {code}
> From ZK client's log, it was able to renew the expired session on 22:05:20.
> {code:java}
> June 27th 2017, 22:05:18.590 INFO org.apache.zookeeper.ClientCnxn Client
> session timed out, have not heard from server in 4485ms for sessionid
> 0x25cd1e82c110001, closing socket connection and attempting reconnect 0
> June 27th 2017, 22:05:18.590 WARN org.apache.zookeeper.ClientCnxn Client
> session timed out, have not heard from server in 4485ms for sessionid
> 0x25cd1e82c110001 0
> June 27th 2017, 22:05:19.325 WARN org.apache.zookeeper.ClientCnxn SASL
> configuration failed: javax.security.auth.login.LoginException: No JAAS
> configuration section named 'Client' was found in specified JAAS
> configuration file: '/opt/confluent/etc/kafka/server_jaas.conf'. Will
> continue connection to Zookeeper server without SASL authentication, if
> Zookeeper server allows it. 0
> June 27th 2017, 22:05:19.326 INFO org.apache.zookeeper.ClientCnxn Opening
> socket connection to server 100.65.188.168/100.65.188.168:2181 0
> June 27th 2017, 22:05:20.324 INFO org.apache.zookeeper.ClientCnxn Socket
> connection established to 100.65.188.168/100.65.188.168:2181, initiating
> session 0
> June 27th 2017, 22:05:20.327 INFO org.apache.zookeeper.ClientCnxn Session
> establishment complete on server 100.65.188.168/100.65.188.168:2181,
> sessionid = 0x25cd1e82c110001, negotiated timeout = 12000 0
> {code}
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