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https://issues.apache.org/jira/browse/HBASE-1394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708338#action_12708338
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stack commented on HBASE-1394:
------------------------------
Thinking more, the log split involves reading in a regionservers commit logs
and dividing up the edits by region. I think we can have an HLog that opens a
pool of N commit logs now with the logger distributing edits over the pool of
log writers. What it would mean is that edits while written in order, as we
spray them across N files, they could be processed out of order as we read them
in; e.g. If 3 logs in the pool, let edit A go into file 1, edit B into file 2
and edit C into file 3 and so one. Since our current basic split process reads
a file at a time, we'd read file 1 and find edits A, then D, and so on.
Processing these files, serially, we'd write the region-scoped edits into new
SequenceFiles -- not sorted MapFiles or hfiles -- of one per region. These
files are then picked up on region open and the edits inserted into memcache
(We read the log on the open of each individual store -- which seems
profligate). The insertion into memcache will put them back into the 'right'
order -- newer edits will sort before older, etc. The only place I see there
possibly being a problem is if you insert a KV with one value and then
afterward insert a KV with exact same r/c/ts coordinates but with different
value. Its possible that this ordering will not be honored on crash. Is that
OK?
> Uploads sometimes fall to 0 requests/second (Binding up on HLog#append?)
> ------------------------------------------------------------------------
>
> Key: HBASE-1394
> URL: https://issues.apache.org/jira/browse/HBASE-1394
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: stack
> Priority: Critical
> Fix For: 0.20.0
>
> Attachments: loghowlongittookappendinghlog.patch
>
>
> Trying to figure why rate sometimes goes to zero.
> Studying the reginoserver, HLog#append looks like a possible culprit.
> {code}
> "IPC Server handler 7 on 60021" daemon prio=10 tid=0x000000004057dc00
> nid=0x1bc4 in Object.wait() [0x0000000043393000..0x0000000043393b80]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> at java.lang.Object.wait(Object.java:485)
> at
> org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.writeChunk(DFSClient.java:2964)
> - locked <0x00007f9e3e449ff0> (a java.util.LinkedList)
> - locked <0x00007f9e3e449e18> (a
> org.apache.hadoop.hdfs.DFSClient$DFSOutputStream)
> at
> org.apache.hadoop.fs.FSOutputSummer.writeChecksumChunk(FSOutputSummer.java:150)
> at org.apache.hadoop.fs.FSOutputSummer.write1(FSOutputSummer.java:100)
> at org.apache.hadoop.fs.FSOutputSummer.write(FSOutputSummer.java:86)
> - locked <0x00007f9e3e449e18> (a
> org.apache.hadoop.hdfs.DFSClient$DFSOutputStream)
> at
> org.apache.hadoop.fs.FSDataOutputStream$PositionCache.write(FSDataOutputStream.java:49)
> at java.io.DataOutputStream.write(DataOutputStream.java:90)
> - locked <0x00007f9e434e5588> (a
> org.apache.hadoop.fs.FSDataOutputStream)
> at
> org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:1020)
> - locked <0x00007f9e434e55c0> (a
> org.apache.hadoop.io.SequenceFile$Writer)
> at
> org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:984)
> - locked <0x00007f9e434e55c0> (a
> org.apache.hadoop.io.SequenceFile$Writer)
> at org.apache.hadoop.hbase.regionserver.HLog.doWrite(HLog.java:565)
> at org.apache.hadoop.hbase.regionserver.HLog.append(HLog.java:521)
> - locked <0x00007f9dfa376f70> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.update(HRegion.java:1777)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.batchUpdate(HRegion.java:1348)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.batchUpdate(HRegion.java:1289)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.batchUpdates(HRegionServer.java:1727)
> at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:642)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:911)
> {code}
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