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https://issues.apache.org/jira/browse/HBASE-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14106794#comment-14106794
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Jean-Marc Spaggiari commented on HBASE-11794:
---------------------------------------------
What's about something like this?
{code}
@Override
public List<Path> flushSnapshot(MemStoreSnapshot snapshot, long
cacheFlushSeqNum,
MonitoredTask status) throws IOException {
int cellsCount = snapshot.getCellsCount();
if (cellsCount == 0) return new ArrayList<Path>(); // don't flush if there
are no entries
long smallestReadPoint = store.getSmallestReadPoint();
InternalScanner scanner = createScanner(snapshot.getScanner(),
smallestReadPoint);
if (scanner == null) {
return new ArrayList<Path>();; // NULL scanner returned from coprocessor
hooks means skip normal processing
}
// Let policy select flush method.
StripeFlushRequest req = this.policy.selectFlush(this.stripes, cellsCount);
boolean success = false;
StripeMultiFileWriter mw = null;
List<Path> result = null;
try {
mw = req.createWriter(); // Writer according to the policy.
StripeMultiFileWriter.WriterFactory factory = createWriterFactory(
snapshot.getTimeRangeTracker(), cellsCount);
StoreScanner storeScanner = (scanner instanceof StoreScanner) ?
(StoreScanner)scanner : null;
mw.init(storeScanner, factory, store.getComparator());
synchronized (flushLock) {
performFlush(scanner, mw, smallestReadPoint);
result = mw.commitWriters(cacheFlushSeqNum, false);
success = true;
}
} finally {
if (!success && (mw != null)) {
if (result != null) {
result.clear();
}
for (Path leftoverFile : mw.abortWriters()) {
try {
store.getFileSystem().delete(leftoverFile, false);
} catch (Exception e) {
LOG.error("Failed to delete a file after failed flush: " + e);
}
}
}
try {
scanner.close();
} catch (IOException ex) {
LOG.warn("Failed to close flush scanner, ignoring", ex);
}
}
return result;
}
{code}
Idea is, if we don't need to return the empty list, then we create an ArrayList
that we loose after when we assign result with mw.commitWriters. I don't know
how often this method is called but this will save one object creation.
> StripeStoreFlusher causes NullPointerException and Region down
> --------------------------------------------------------------
>
> Key: HBASE-11794
> URL: https://issues.apache.org/jira/browse/HBASE-11794
> Project: HBase
> Issue Type: Bug
> Components: Compaction
> Affects Versions: 0.98.3, 0.98.4, 0.98.5
> Reporter: jeongmin kim
> Priority: Critical
> Attachments: HBASE_11794.patch
>
>
> StoreFlusher.flushSnapshot() mustn't return null value.
> But StripeStoreFlusher.flushSnapshot() does.
> It cause NullPointerException at
> org.apache.hadoop.hbase.regionserver.HStore.flushCache(HStore.java:802)
> and this makes regions dead after exhaustive retries and no recovery
> available from it.
> the code (StripeStoreFlusher:64) has to be changed
> ===============
> from
> List<Path> result = null
> to
> List<Path> result = new ArrayList<Path>();
> ===============
> to return a empty list not null value.
>
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