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https://issues.apache.org/jira/browse/ZOOKEEPER-1599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13533597#comment-13533597
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Skye Wanderman-Milne commented on ZOOKEEPER-1599:
-------------------------------------------------
A 3.4 leader will very likely repeatedly try and fail to become the leader
since voting is basically deterministic (basically if a server is up-to-date
and has the highest server id, it will always be elected leader AFAIK). No one
else will get a quorum because no one else will be elected leader, so they
won't even try.
It sounds like we should patch 3.3 so that it can speak both protocols. This
way we're not introducing regressions into 3.4 by supporting the old protocol
(even though you'll only hit the bugs when upgrading from 3.3), and if you want
to avoid downtime you can first upgrade to 3.3.7 and then to 3.4. Does this
make sense?
> 3.3 server cannot join 3.4 quorum
> ---------------------------------
>
> Key: ZOOKEEPER-1599
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1599
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Affects Versions: 3.3.6, 3.4.5
> Reporter: Skye Wanderman-Milne
> Assignee: Skye Wanderman-Milne
> Priority: Blocker
> Fix For: 3.4.6
>
> Attachments: ZOOKEEPER-1599.patch
>
>
> When a 3.3 server attempts to join an existing quorum lead by a 3.4 server,
> the 3.3 server is disconnected while trying to download the leader's
> snapshot. The 3.3 server restarts and starts the process over again, but is
> never able to join the quorum.
> 3.3 server log:
> {code}
> 2012-12-07 10:44:34,582 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Learner@294] - Getting a snapshot from
> leader
> 2012-12-07 10:44:34,582 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Learner@325] - Setting leader epoch 12
> 2012-12-07 10:44:54,604 - WARN
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Follower@82] - Exception when following the
> leader
> java.io.EOFException
> at java.io.DataInputStream.readInt(DataInputStream.java:392)
> at
> org.apache.jute.BinaryInputArchive.readInt(BinaryInputArchive.java:63)
> at
> org.apache.zookeeper.server.quorum.QuorumPacket.deserialize(QuorumPacket.java:84)
> at
> org.apache.jute.BinaryInputArchive.readRecord(BinaryInputArchive.java:108)
> at
> org.apache.zookeeper.server.quorum.Learner.readPacket(Learner.java:148)
> at
> org.apache.zookeeper.server.quorum.Learner.syncWithLeader(Learner.java:332)
> at
> org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:75)
> at
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:645)
> 2012-12-07 10:44:54,605 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Follower@165] - shutdown called
> java.lang.Exception: shutdown Follower
> at
> org.apache.zookeeper.server.quorum.Follower.shutdown(Follower.java:165)
> at
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:649)
> {code}
> 3.4 leader log:
> {code}
> 2012-12-07 10:51:35,178 [myid:2] - INFO
> [WorkerReceiver[myid=2]:FastLeaderElection$Messenger$WorkerReceiver@273] -
> Backward compatibility mode, server id=3
> 2012-12-07 10:51:35,178 [myid:2] - INFO
> [WorkerReceiver[myid=2]:FastLeaderElection@542] - Notification: 3 (n.leader),
> 0x1100000000 (n.zxid), 0x2 (n.round), LOOKING (n.state), 3 (n.sid), 0x11
> (n.peerEPoch), LEADING (my state)
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@263] - Follower sid: 3 : info
> : org.apache.zookeeper.server.quorum.QuorumPeer$QuorumServer@262f4873
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@318] - Synchronizing with
> Follower sid: 3 maxCommittedLog=0x0 minCommittedLog=0x0
> peerLastZxid=0x1100000000
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@395] - Sending SNAP
> 2012-12-07 10:51:35,183 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@419] - Sending snapshot last
> zxid of peer is 0x1100000000 zxid of leader is 0x1200000000sent zxid of db
> as 0x1200000000
> 2012-12-07 10:51:55,204 [myid:2] - ERROR
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@562] - Unexpected exception
> causing shutdown while sock still open
> java.net.SocketTimeoutException: Read timed out
> at java.net.SocketInputStream.socketRead0(Native Method)
> at java.net.SocketInputStream.read(SocketInputStream.java:150)
> at java.net.SocketInputStream.read(SocketInputStream.java:121)
> at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
> at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
> at java.io.DataInputStream.readInt(DataInputStream.java:387)
> at
> org.apache.jute.BinaryInputArchive.readInt(BinaryInputArchive.java:63)
> at
> org.apache.zookeeper.server.quorum.QuorumPacket.deserialize(QuorumPacket.java:83)
> at
> org.apache.jute.BinaryInputArchive.readRecord(BinaryInputArchive.java:108)
> at
> org.apache.zookeeper.server.quorum.LearnerHandler.run(LearnerHandler.java:450)
> 2012-12-07 10:51:55,205 [myid:2] - WARN
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@575] - ******* GOODBYE
> /127.0.0.1:37654 ********
> {code}
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