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https://issues.apache.org/jira/browse/HBASE-11099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14215623#comment-14215623
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Stephen Yuan Jiang commented on HBASE-11099:
--------------------------------------------
The warnings from javadoc are NOT from this patch:
{noformat}
[WARNING] Javadoc Warnings
[WARNING]
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java:54:
warning: Unsafe is internal proprietary API and may be removed in a future
release
[WARNING] import sun.misc.Unsafe;
[WARNING] ^
[WARNING] Javadoc Warnings
[WARNING]
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java:603:
warning - @param argument "regionserver" is not a parameter name.
[WARNING] Javadoc Warnings
[WARNING]
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/hbase-server/src/main/java/org/apache/hadoop/hbase/mapreduce/TableOutputFormat.java:92:
warning - @param argument "<KEY>" is not a type parameter name.
{noformat}
> 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: 0.99.1
> Reporter: Jeffrey Zhong
> Assignee: Stephen Yuan Jiang
> Fix For: 1.0.0, 2.0.0, 0.99.2
>
> Attachments: HBASE-11099.v1-2.0.patch
>
>
> 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.
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