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
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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