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https://issues.apache.org/jira/browse/ZOOKEEPER-1560?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13483426#comment-13483426
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Skye Wanderman-Milne commented on ZOOKEEPER-1560:
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A couple questions/concerns:
- Is it safe to write out the whole packet in a while loop? Doing so
essentially causes the thread to block until everything is written. This seems
pretty dangerous to me since there's only a single SendThread -- I think it
would be safer to take the current approach of only doing one socket write per
invocation of doIO. We would still need to address issue 1 in the description
(packets are being removed from the queue even if they weren't fully written).
- What is the purpose of chunking the data? Why not write as much as possible?
- This was commented on earlier, but what's going on with issues 2 and 3 from
the description? Addressing only issue 1 seems to fix the problem of sending
large packets.
> Zookeeper client hangs on creation of large nodes
> -------------------------------------------------
>
> Key: ZOOKEEPER-1560
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1560
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Affects Versions: 3.4.4, 3.5.0
> Reporter: Igor Motov
> Assignee: Ted Yu
> Fix For: 3.5.0, 3.4.5
>
> Attachments: ZOOKEEPER-1560.patch, zookeeper-1560-v1.txt,
> zookeeper-1560-v2.txt, zookeeper-1560-v3.txt, zookeeper-1560-v4.txt,
> zookeeper-1560-v5.txt, zookeeper-1560-v6.txt, zookeeper-1560-v7.txt
>
>
> To reproduce, try creating a node with 0.5M of data using java client. The
> test will hang waiting for a response from the server. See the attached patch
> for the test that reproduces the issue.
> It seems that ZOOKEEPER-1437 introduced a few issues to
> {{ClientCnxnSocketNIO.doIO}} that prevent {{ClientCnxnSocketNIO}} from
> sending large packets that require several invocations of
> {{SocketChannel.write}} to complete. The first issue is that the call to
> {{outgoingQueue.removeFirstOccurrence(p);}} removes the packet from the queue
> even if the packet wasn't completely sent yet. It looks to me that this call
> should be moved under {{if (!pbb.hasRemaining())}} The second issue is that
> {{p.createBB()}} is reinitializing {{ByteBuffer}} on every iteration, which
> confuses {{SocketChannel.write}}. And the third issue is caused by extra
> calls to {{cnxn.getXid()}} that increment xid on every iteration and confuse
> the server.
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