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https://issues.apache.org/jira/browse/HBASE-5689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13243109#comment-13243109
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ramkrishna.s.vasudevan commented on HBASE-5689:
-----------------------------------------------
I just want to understand here like removing the
{code}
if (maxSeqId <= minSeqId) {
String msg = "Maximum possible sequenceid for this log is " + maxSeqId
+ ", skipped the whole file, path=" + edits;
LOG.debug(msg);
continue;
{code}
'continue' here should solve the problem. Inside replayRecoveredEdits we have
this code
{code}
// Now, figure if we should skip this edit.
if (key.getLogSeqNum() <= currentEditSeqId) {
skippedEdits++;
continue;
}
{code}
which will any way skip unnecessary edits. I tried by commenting the
'continue' in the code and the test case that you gave passed. It is my
thought, your comments are welcome.
> Skip RecoveredEdits may cause data loss
> ---------------------------------------
>
> Key: HBASE-5689
> URL: https://issues.apache.org/jira/browse/HBASE-5689
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: chunhui shen
> Assignee: chunhui shen
> Attachments: 5689-testcase.patch, HBASE-5689.patch
>
>
> Let's see the following scenario:
> 1.Region is on the server A
> 2.put KV(r1->v1) to the region
> 3.move region from server A to server B
> 4.put KV(r2->v2) to the region
> 5.move region from server B to server A
> 6.put KV(r3->v3) to the region
> 7.kill -9 server B and start it
> 8.kill -9 server A and start it
> 9.scan the region, we could only get two KV(r1->v1,r2->v2), the third
> KV(r3->v3) is lost.
> Let's analyse the upper scenario from the code:
> 1.the edit logs of KV(r1->v1) and KV(r3->v3) are both recorded in the same
> hlog file on server A.
> 2.when we split server B's hlog file in the process of ServerShutdownHandler,
> we create one RecoveredEdits file f1 for the region.
> 2.when we split server A's hlog file in the process of ServerShutdownHandler,
> we create another RecoveredEdits file f2 for the region.
> 3.however, RecoveredEdits file f2 will be skiped when initializing region
> HRegion#replayRecoveredEditsIfAny
> {code}
> for (Path edits: files) {
> if (edits == null || !this.fs.exists(edits)) {
> LOG.warn("Null or non-existent edits file: " + edits);
> continue;
> }
> if (isZeroLengthThenDelete(this.fs, edits)) continue;
> if (checkSafeToSkip) {
> Path higher = files.higher(edits);
> long maxSeqId = Long.MAX_VALUE;
> if (higher != null) {
> // Edit file name pattern, HLog.EDITFILES_NAME_PATTERN: "-?[0-9]+"
> String fileName = higher.getName();
> maxSeqId = Math.abs(Long.parseLong(fileName));
> }
> if (maxSeqId <= minSeqId) {
> String msg = "Maximum possible sequenceid for this log is " +
> maxSeqId
> + ", skipped the whole file, path=" + edits;
> LOG.debug(msg);
> continue;
> } else {
> checkSafeToSkip = false;
> }
> }
> {code}
>
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