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https://issues.apache.org/jira/browse/HBASE-6065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13280788#comment-13280788
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chunhui shen commented on HBASE-6065:
-------------------------------------
bq.updateRegionMaximumEditLogSeqNum() is called by two methods. I think we
should make it synchronized
In the patch v2, I has already added synchronized
{code}
void updateRegionMaximumEditLogSeqNum(Entry entry) {
- regionMaximumEditLogSeqNum.put(entry.getKey().getEncodedRegionName(),
- entry.getKey().getLogSeqNum());
+ synchronized (regionMaximumEditLogSeqNum) {
+ Long
currentMaxSeqNum=regionMaximumEditLogSeqNum.get(entry.getKey().getEncodedRegionName());
+ if (currentMaxSeqNum == null
+ || entry.getKey().getLogSeqNum() > currentMaxSeqNum) {
+ regionMaximumEditLogSeqNum.put(entry.getKey().getEncodedRegionName(),
+ entry.getKey().getLogSeqNum());
+ }
+ }
{code}
> Log for flush would append a non-sequential edit in the hlog， may cause data
> loss
> ---------------------------------------------------------------------------------
>
> Key: HBASE-6065
> URL: https://issues.apache.org/jira/browse/HBASE-6065
> Project: HBase
> Issue Type: Bug
> Components: wal
> Reporter: chunhui shen
> Assignee: chunhui shen
> Priority: Critical
> Attachments: HBASE-6065.patch, HBASE-6065v2.patch
>
>
> After completing flush region, we will append a log edit in the hlog file
> through HLog#completeCacheFlush.
> {code}
> public void completeCacheFlush(final byte [] encodedRegionName,
> final byte [] tableName, final long logSeqId, final boolean
> isMetaRegion)
> {
> ...
> HLogKey key = makeKey(encodedRegionName, tableName, logSeqId,
> System.currentTimeMillis(), HConstants.DEFAULT_CLUSTER_ID);
> ...
> }
> {code}
> when we make the hlog key, we use the seqId from the parameter, and it is
> generated by HLog#startCacheFlush,
> Here, we may append a lower seq id edit than the last edit in the hlog file.
> If it is the last edit log in the file, it may cause data loss.
> because
> {code}
> HRegion#replayRecoveredEditsIfAny{
> ...
> maxSeqId = Math.abs(Long.parseLong(fileName));
> if (maxSeqId <= minSeqId) {
> String msg = "Maximum sequenceid for this log is " + maxSeqId
> + " and minimum sequenceid for the region is " + minSeqId
> + ", skipped the whole file, path=" + edits;
> LOG.debug(msg);
> continue;
> }
> ...
> }
> {code}
> We may skip the splitted log file, because we use the lase edit's seq id as
> its file name, and consider this seqId as the max seq id in this log file.
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