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https://issues.apache.org/jira/browse/ZOOKEEPER-1599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531281#comment-13531281
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Alexander Shraer commented on ZOOKEEPER-1599:
---------------------------------------------
Thanks, Skye. Another reason not to support this is that an earlier version of
ZooKeeper server may not always understand or be able to correctly execute
commands sent by a leader running a later version. I'm not sure about 3.3 vs
3.4 (MultiOp ?) but in 3.5 I hope to see ZK-107 go in, and then there will be
new reconfiguration commands which 3.4 will not be able to process correctly.
One may try to avoid such outages by upgrading the leader last.
> 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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