Jeffrey Zhong created HBASE-11099:
-------------------------------------
Summary: Two situations where we could open a region with smaller
sequence number
Key: HBASE-11099
URL: https://issues.apache.org/jira/browse/HBASE-11099
Project: HBase
Issue Type: Bug
Components: regionserver
Affects Versions: 0.99.0
Reporter: Jeffrey Zhong
Recently I happened to run into code where we potentially could open region
with smaller sequence number:
1) Inside function: HRegion#internalFlushcache. This is due to we change the
way WAL Sync where we use late binding(assign sequence number right before wal
sync).
The flushSeqId may less than the change sequence number included in the flush
which may cause later region opening code to use a smaller than expected
sequence number when we reopen the region.
{code}
flushSeqId = this.sequenceId.incrementAndGet();
...
mvcc.waitForRead(w);
{code}
2) HRegion#replayRecoveredEdits where we have following code:
{code}
...
if (coprocessorHost != null) {
status.setStatus("Running pre-WAL-restore hook in coprocessors");
if (coprocessorHost.preWALRestore(this.getRegionInfo(), key, val)) {
// if bypass this log entry, ignore it ...
continue;
}
}
...
currentEditSeqId = key.getLogSeqNum();
{code}
If coprocessor skip some tail WALEdits, then the function will return smaller
currentEditSeqId. In the end, a region may also open with a smaller sequence
number. This may cause data loss because Master may record a larger flushed
sequence Id and some WALEdits maybe skipped during recovery if the region fail
again.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
