[ https://issues.apache.org/jira/browse/HBASE-18168?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Allan Yang updated HBASE-18168: ------------------------------- Attachment: HBASE-18168-branch-1.1.patch > NoSuchElementException when rolling the log > ------------------------------------------- > > Key: HBASE-18168 > URL: https://issues.apache.org/jira/browse/HBASE-18168 > Project: HBase > Issue Type: Bug > Affects Versions: 1.1.11 > Reporter: Allan Yang > Assignee: Allan Yang > Attachments: HBASE-18168-branch-1.1.patch > > > Today, one of our server aborted due to the following log. > {code} > 2017-06-06 05:38:47,142 ERROR [regionserver/xxxx.logRoller] > regionserver.LogRoller: Log rolling failed > java.util.NoSuchElementException > at > java.util.concurrent.ConcurrentSkipListMap$Iter.advance(ConcurrentSkipListMap.java:2224) > at > java.util.concurrent.ConcurrentSkipListMap$ValueIterator.next(ConcurrentSkipListMap.java:2253) > at java.util.Collections.min(Collections.java:628) > at > org.apache.hadoop.hbase.regionserver.wal.FSHLog.findEligibleMemstoresToFlush(FSHLog.java:861) > at > org.apache.hadoop.hbase.regionserver.wal.FSHLog.findRegionsToForceFlush(FSHLog.java:886) > at > org.apache.hadoop.hbase.regionserver.wal.FSHLog.rollWriter(FSHLog.java:728) > at > org.apache.hadoop.hbase.regionserver.LogRoller.run(LogRoller.java:137) > at java.lang.Thread.run(Thread.java:756) > 2017-06-06 05:38:47,142 FATAL [regionserver/xxxx.logRoller] > regionserver.HRegionServer: ABORTING region server xxxx: Log rolling failed > java.util.NoSuchElementException > ...... > {code} > The code is here: > {code} > private byte[][] findEligibleMemstoresToFlush(Map<byte[], Long> > regionsSequenceNums) { > List<byte[]> regionsToFlush = null; > // Keeping the old behavior of iterating unflushedSeqNums under > oldestSeqNumsLock. > synchronized (regionSequenceIdLock) { > for (Map.Entry<byte[], Long> e: regionsSequenceNums.entrySet()) { > ConcurrentMap<byte[], Long> m = > this.oldestUnflushedStoreSequenceIds.get(e.getKey()); > if (m == null) { > continue; > } > long unFlushedVal = Collections.min(m.values()); //The exception is > thrown here > ...... > {code} > The map 'm' is empty is the only reason I can think of why > NoSuchElementException is thrown. I then looked up all code related to the > update of 'oldestUnflushedStoreSequenceIds'. All update to > 'oldestUnflushedStoreSequenceIds' is guarded by the synchronization of > 'regionSequenceIdLock' except here: > {code} > private ConcurrentMap<byte[], Long> > getOrCreateOldestUnflushedStoreSequenceIdsOfRegion( > byte[] encodedRegionName) { > ...... > oldestUnflushedStoreSequenceIdsOfRegion = > new ConcurrentSkipListMap<byte[], Long>(Bytes.BYTES_COMPARATOR); > ConcurrentMap<byte[], Long> alreadyPut = > oldestUnflushedStoreSequenceIds.putIfAbsent(encodedRegionName, > oldestUnflushedStoreSequenceIdsOfRegion); // Here, a empty map may > put to 'oldestUnflushedStoreSequenceIds' with no synchronization > return alreadyPut == null ? oldestUnflushedStoreSequenceIdsOfRegion : > alreadyPut; > } > {code} > It should be a very rare bug. But it can lead to server abort. It only exists > in branch-1.1. -- This message was sent by Atlassian JIRA (v6.3.15#6346)