Andrew Purtell created HBASE-20895:
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Summary: NPE in RpcServer#readAndProcess
Key: HBASE-20895
URL: https://issues.apache.org/jira/browse/HBASE-20895
Project: HBase
Issue Type: Bug
Components: rpc
Affects Versions: 1.3.2
Reporter: Andrew Purtell
Assignee: Monani Mihir
Fix For: 1.5.0, 1.3.3, 1.4.6
{noformat}
2018-07-10 16:25:55,005 DEBUG [.sfdc.net,port=60020] ipc.RpcServer -
RpcServer.listener,port=60020: Caught exception while reading:
java.lang.NullPointerException
at
org.apache.hadoop.hbase.ipc.RpcServer$Connection.readAndProcess(RpcServer.java:1761)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener.doRead(RpcServer.java:949)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.doRunLoop(RpcServer.java:730)
at
org.apache.hadoop.hbase.ipc.RpcServer$Listener$Reader.run(RpcServer.java:706)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
{noformat}
This looks like it could be a use after close problem if there is concurrent
access to a Connection.
In process() we might store a null back to the 'data' field.
Meanwhile in readAndProcess() we have a case where we might be blocked on a
channel read and then after coming back from the read we go to use 'data' after
a null has been written back, leading to a NPE.
{quote}
count = channelRead(channel, data);
1761 ---> if (count >= 0 && *data.remaining()* == 0) { // count==0 if
dataLength == 0
process();
}
{quote}
Whether a NPE happens or not is going to depend on the timing of the store back
to 'data' in another thread and use of 'data' in this thread and whether or not
the JVM has optimized away a reload of 'data' (it's not declared volatile)
We should do a null check here just to be defensive. We should also look at
whether the concurrent access to the Connection is intended.
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