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https://issues.apache.org/jira/browse/HDFS-13977?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16912740#comment-16912740
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Chen Liang commented on HDFS-13977:
-----------------------------------
v002 patch looks pretty good to me, and good discussions! just one minor
comment.
{code:java}
if (size >= ipcMaxDataLength) {
throw new IllegalArgumentException("Attempted to set an output buffer "
+ "capacity (" + size + ") which is less than the IPC max data length ("
+ ipcMaxDataLength + "). This will cause journals to reject edits.");
}
{code}
Shouldn't it be "large than" instead of "less than" here? Also, looks like
output buffer capacity can not be set, it is hard coded to 512K, it is the IPC
data length that can be set here. So I think it would be more clear to state
the error the other way. i.e. something like "attempted to set IPC length less
than buffer capacity"
> NameNode can kill itself if it tries to send too many txns to a QJM
> simultaneously
> ----------------------------------------------------------------------------------
>
> Key: HDFS-13977
> URL: https://issues.apache.org/jira/browse/HDFS-13977
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode, qjm
> Affects Versions: 2.7.7
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Major
> Attachments: HDFS-13977.000.patch, HDFS-13977.001.patch,
> HDFS-13977.002.patch
>
>
> h3. Problem & Logs
> We recently encountered an issue on a large cluster (running 2.7.4) in which
> the NameNode killed itself because it was unable to communicate with the JNs
> via QJM. We discovered that it was the result of the NameNode trying to send
> a huge batch of over 1 million transactions to the JNs in a single RPC:
> {code:title=NameNode Logs}
> WARN org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager: Remote
> journal X.X.X.X:XXXX failed to
> write txns 10000000-11153636. Will try to write to this JN again after the
> next log roll.
> ...
> WARN org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager: Took 1098ms
> to send a batch of 1153637 edits (335886611 bytes) to remote journal
> X.X.X.X:XXXX
> {code}
> {code:title=JournalNode Logs}
> INFO org.apache.hadoop.ipc.Server: Socket Reader #1 for port 8485:
> readAndProcess from client X.X.X.X threw exception [java.io.IOException:
> Requested data length 335886776 is longer than maximum configured RPC length
> 67108864. RPC came from X.X.X.X]
> java.io.IOException: Requested data length 335886776 is longer than maximum
> configured RPC length 67108864. RPC came from X.X.X.X
> at
> org.apache.hadoop.ipc.Server$Connection.checkDataLength(Server.java:1610)
> at
> org.apache.hadoop.ipc.Server$Connection.readAndProcess(Server.java:1672)
> at org.apache.hadoop.ipc.Server$Listener.doRead(Server.java:897)
> at
> org.apache.hadoop.ipc.Server$Listener$Reader.doRunLoop(Server.java:753)
> at org.apache.hadoop.ipc.Server$Listener$Reader.run(Server.java:724)
> {code}
> The JournalNodes rejected the RPC because it had a size well over the 64MB
> default {{ipc.maximum.data.length}}.
> This was triggered by a huge number of files all hitting a hard lease timeout
> simultaneously, causing the NN to force-close them all at once. This can be a
> particularly nasty bug as the NN will attempt to re-send this same huge RPC
> on restart, as it loads an fsimage which still has all of these open files
> that need to be force-closed.
> h3. Proposed Solution
> To solve this we propose to modify {{EditsDoubleBuffer}} to add a "hard
> limit" based on the value of {{ipc.maximum.data.length}}. When {{writeOp()}}
> or {{writeRaw()}} is called, first check the size of {{bufCurrent}}. If it
> exceeds the hard limit, block the writer until the buffer is flipped and
> {{bufCurrent}} becomes {{bufReady}}. This gives some self-throttling to
> prevent the NameNode from killing itself in this way.
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