Chia-Ping Tsai created HBASE-18158:
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Summary: Two running in-memory compaction threads may lose data
Key: HBASE-18158
URL: https://issues.apache.org/jira/browse/HBASE-18158
Project: HBase
Issue Type: Bug
Affects Versions: 2.0.0
Reporter: Chia-Ping Tsai
Fix For: 2.0.0
{code:title=CompactingMemStore.java|borderStyle=solid}
private void stopCompaction() {
if (inMemoryFlushInProgress.get()) {
compactor.stop();
inMemoryFlushInProgress.set(false);
}
}
{code}
The stopCompaction() set inMemoryFlushInProgress to false so there may be two
in-memory compaction thread are executed simultaneously. If there are two
running InMemoryFlushRunnable, the later InMemoryFlushRunnable may change the
versionedList.
{code:title=MemStoreCompactor.java|borderStyle=solid}
public boolean start() throws IOException {
if (!compactingMemStore.hasImmutableSegments()) { // no compaction on empty
pipeline
return false;
}
// get a snapshot of the list of the segments from the pipeline,
// this local copy of the list is marked with specific version
versionedList = compactingMemStore.getImmutableSegments();
{code}
And the first InMemoryFlushRunnable will use the chagned versionedList to
remove the corresponding segments.
{code:title=MemStoreCompactor#doCompaction|borderStyle=solid}
if (!isInterrupted.get()) {
if (resultSwapped = compactingMemStore.swapCompactedSegments(
versionedList, result, (action==Action.MERGE))) {
// update the wal so it can be truncated and not get too long
compactingMemStore.updateLowestUnflushedSequenceIdInWAL(true); //
only if greater
}
}
{code}
In conclusion, first InMemoryFlushRunnable will remove the worng segment. And
the later InMemoryFlushRunnable will introduce NPE because first
InMemoryFlushRunnable set versionedList to null after compaction.
{code}
Exception in thread
"RpcServer.default.FPBQ.Fifo.handler=3,queue=0,port=45712-inmemoryCompactions-1496563908038"
java.lang.NullPointerException
at
org.apache.hadoop.hbase.regionserver.CompactionPipeline.swap(CompactionPipeline.java:119)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore.swapCompactedSegments(CompactingMemStore.java:283)
at
org.apache.hadoop.hbase.regionserver.MemStoreCompactor.doCompaction(MemStoreCompactor.java:212)
at
org.apache.hadoop.hbase.regionserver.MemStoreCompactor.start(MemStoreCompactor.java:122)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore.flushInMemory(CompactingMemStore.java:388)
at
org.apache.hadoop.hbase.regionserver.CompactingMemStore$InMemoryFlushRunnable.run(CompactingMemStore.java:500)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
{code}
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