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https://issues.apache.org/jira/browse/HBASE-11277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14014315#comment-14014315
]
Andrew Purtell commented on HBASE-11277:
----------------------------------------
I'm running YCSB's workload A on a well endowed EC2 testbed with 10GE
networking against a table preloaded with 100M entries, running 5 instances of
the YCSB client with 10 threads on 5 separate client servers. The clients are
attempting 10M ops at a target rate of 100,000 ops/second in aggregate. (I also
tried an aggregate target of 250,000 ops/sec but this might have been
triggering EC2 / kernel / networking issues.)
I added a tiny bit of code to RpcServer.Reader#readAndProcess that throws an
IOE if we go 100,000 times around the readAndProcess loop and it was triggered
maybe 2-3 times on every server during a run. I then changed the limit to
10,000 with better results but many more exceptions observed, maybe ~20 per
server per test run. They look like:
{noformat}
2014-05-30 20:58:40,637 WARN [RpcServer.reader=3,port=8120] ipc.RpcServer:
RpcServer.listener,port=8120: count of bytes read: 0
java.io.IOException: readAndProcess waited too long for message data:
client=10.220.3.99 authMethod=SIMPLE connectionPreambleRead=true
connectionHeaderRead=true data.remaining=624118 data.limit=644612
at
org.apache.hadoop.hbase.ipc.RpcServer$Connection.readAndProcess(RpcServer.java:1411)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener.doRead(RpcServer.java:790)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.doRunLoop(RpcServer.java:581)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.run(RpcServer.java:556)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
{noformat}
In truth readAndProcess isn't waiting very long. Readers are pulled from a pool
to handle channels that become readable. In the message processing connection
phase, they read 4 bytes of length and then want to read exactly those many
additional bytes in a blocking manner. During this process if data is not
temporarily available on the channel we will spin hard on channelRead. The IOE
I added short circuits this by closing the connection and forcing a retry.
The spinning is bad. We might want to yield the thread or introduce a small
sleep. Better yet would be a fully async server side.
Dropping the connection almost seems like a good idea. Without doing that one
of the client (multiplexed) connections stops making progress for periods of
20-40 seconds. If we do drop the connection, the test sustains an average
100,000 ops/sec.
> RPCServer threads can wedge under high load
> -------------------------------------------
>
> Key: HBASE-11277
> URL: https://issues.apache.org/jira/browse/HBASE-11277
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.96.2, 0.98.3
> Reporter: Andrew Purtell
> Priority: Critical
>
> This is with 0.98.0 in an insecure setup with 7u55 and 7u60. Under high load,
> RPCServer threads can wedge, fail to make progess, and consume 100% CPU time
> on a core indefinitely.
> Dumping threads, all threads are in BLOCKED or IN_NATIVE state. The IN_NATIVE
> threads are mostly in EPollArrayWrapper.epollWait or
> FileDispatcherImpl.read0. The number of threads found in
> FileDispatcherImpl.read0 correspond to the number of runaway threads expected
> based on looking at 'top' output. These look like:
> {noformat}
> Thread 64758: (state = IN_NATIVE)
> - sun.nio.ch.FileDispatcherImpl.read0(java.io.FileDescriptor, long, int)
> @bci=0 (Compiled frame; information may be imprecise)
> - sun.nio.ch.SocketDispatcher.read(java.io.FileDescriptor, long, int)
> @bci=4, line=39 (Compiled frame)
> - sun.nio.ch.IOUtil.readIntoNativeBuffer(java.io.FileDescriptor,
> java.nio.ByteBuffer, long, sun.nio.ch.NativeDispatcher) @bci=114, line=223
> (Compil
> ed frame)
> - sun.nio.ch.IOUtil.read(java.io.FileDescriptor, java.nio.ByteBuffer, long,
> sun.nio.ch.NativeDispatcher) @bci=48, line=197 (Compiled frame)
> - sun.nio.ch.SocketChannelImpl.read(java.nio.ByteBuffer) @bci=234, line=379
> (Compiled frame)
> -
> org.apache.hadoop.hbase.ipc.RpcServer.channelRead(java.nio.channels.ReadableByteChannel,
> java.nio.ByteBuffer) @bci=12, line=2224 (Compiled frame)
> - org.apache.hadoop.hbase.ipc.RpcServer$Connection.readAndProcess()
> @bci=509, line=1488 (Compiled frame)
> -
> org.apache.hadoop.hbase.ipc.RpcServer$Listener.doRead(java.nio.channels.SelectionKey)
> @bci=23, line=790 (Compiled frame)
> - org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.doRunLoop() @bci=97,
> line=581 (Compiled frame)
> - org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.run() @bci=1,
> line=556 (Interpreted frame)
> -
> java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker)
> @bci=95, line=1145 (Interpreted frame)
> - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=615
> (Interpreted frame)
> - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame)
> {noformat}
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