Istvan Fajth created HDDS-2347:
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Summary: XCeiverClientGrpc's parallel use leads to NPE
Key: HDDS-2347
URL: https://issues.apache.org/jira/browse/HDDS-2347
Project: Hadoop Distributed Data Store
Issue Type: Improvement
Components: Ozone Client
Reporter: Istvan Fajth
Assignee: Istvan Fajth
This issue came up when testing Hive with ORC tables on Ozone storage backend,
I so far I could not reproduce it locally within a JUnit test but the issue.
I am attaching a diff file that shows what logging I have added in
XCevierClientGrpc and in KeyInputStream to get the results that made me arrive
to the following understanding of the scenario:
- Hive starts a couple of threads to work on the table data during query
execution
- There is one RPCClient that is being used by these threads
- The threads are opening different stream to read from the same key in ozone
- The InputStreams internally are using the same XCeiverClientGrpc
- XCeiverClientGrpc throws the following NPE intermittently:
{code}
Caused by: java.lang.NullPointerException
at
org.apache.hadoop.hdds.scm.XceiverClientGrpc.sendCommandAsync(XceiverClientGrpc.java:398)
at
org.apache.hadoop.hdds.scm.XceiverClientGrpc.sendCommandWithRetry(XceiverClientGrpc.java:295)
at
org.apache.hadoop.hdds.scm.XceiverClientGrpc.sendCommandWithTraceIDAndRetry(XceiverClientGrpc.java:259)
at
org.apache.hadoop.hdds.scm.XceiverClientGrpc.sendCommand(XceiverClientGrpc.java:242)
at
org.apache.hadoop.hdds.scm.storage.ContainerProtocolCalls.getBlock(ContainerProtocolCalls.java:118)
at
org.apache.hadoop.hdds.scm.storage.BlockInputStream.getChunkInfos(BlockInputStream.java:169)
at
org.apache.hadoop.hdds.scm.storage.BlockInputStream.initialize(BlockInputStream.java:118)
at
org.apache.hadoop.hdds.scm.storage.BlockInputStream.read(BlockInputStream.java:224)
at
org.apache.hadoop.ozone.client.io.KeyInputStream.read(KeyInputStream.java:173)
at
org.apache.hadoop.fs.ozone.OzoneFSInputStream.read(OzoneFSInputStream.java:52)
at org.apache.hadoop.fs.FSInputStream.read(FSInputStream.java:75)
at org.apache.hadoop.fs.FSInputStream.readFully(FSInputStream.java:121)
at
org.apache.hadoop.fs.FSDataInputStream.readFully(FSDataInputStream.java:112)
at org.apache.orc.impl.ReaderImpl.extractFileTail(ReaderImpl.java:555)
at org.apache.orc.impl.ReaderImpl.<init>(ReaderImpl.java:370)
at
org.apache.hadoop.hive.ql.io.orc.ReaderImpl.<init>(ReaderImpl.java:61)
at
org.apache.hadoop.hive.ql.io.orc.OrcFile.createReader(OrcFile.java:105)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator.populateAndCacheStripeDetails(OrcInputFormat.java:1708)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator.callInternal(OrcInputFormat.java:1596)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator.access$2900(OrcInputFormat.java:1383)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator$1.run(OrcInputFormat.java:1568)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator$1.run(OrcInputFormat.java:1565)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1876)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator.call(OrcInputFormat.java:1565)
at
org.apache.hadoop.hive.ql.io.orc.OrcInputFormat$SplitGenerator.call(OrcInputFormat.java:1383)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
{code}
I have two proposals to fix this issue, one is the easy answer to put
synchronization to the XCeiverClientGrpc code, the other one is a bit more
complicated, let me explain below.
Naively I would assume that when I get a client SPI instance from
XCeiverClientManager, that instance is ready to use. In fact it is not, and
when the user of the SPI instance sends the first request that is the point
when the client gets essentially ready. Now if we put synchronization to this
code, that is the easy solution, but my pragmatic half screams for a better
solution, that ensures that the Manager essentially manages the clients that is
giving to it's users, and the clients themselves are not getting ready by
accident.
I am working on a proposal that moves things around a bit, and looking for
possible other solutions that does not feel hacky as I feel with the easy
solution.
I am attaching the followings:
- a diff that shows the added extended logging in XCeiverClientGrpc and
KeyInputStream.
- a job log snippet from a Hive query that shows the relevant output from the
extensive logging added by the diff in a cluster.
- later a proposal for the fix I need to work on a bit more
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