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https://issues.apache.org/jira/browse/ZOOKEEPER-1560?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13483544#comment-13483544
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Skye Wanderman-Milne commented on ZOOKEEPER-1560:
-------------------------------------------------
The benefit of one socket write per invocation is that it frees up the
SendThread to perform other actions in between writes. For instance, it looks
like the SendThread is also response for reading incoming data in doIO. I'm not
sure what the consequences of having the thread block until the whole packet is
written are; it might be ok, but if we can avoid looping it might save us some
trouble later.
The next invocation of doIO should continue writing any remaining data from a
previous packet (we don't want to mix up data from different packets). However,
I'm not sure the current code will do this correctly -- I think it's possible
for another packet to be pushed onto the queue while another packet is in the
middle of being written. I'm going to look into this further.
> 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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