[
https://issues.apache.org/jira/browse/HBASE-16162?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Anoop Sam John updated HBASE-16162:
-----------------------------------
Attachment: HBASE-16162_V4.patch
Done bit of a change such that the allowCompaction boolen is called only once
in the flow. ie. Just before in memory compaction. This is after active pushed
to pipeline. I have kept the meaning of the variable as is.
It was bit strange that in the normal code flow, this variable was deciding
even the active segment push to pipeline and compaction where as with in the
flushInMemory() method (and so in test path) it was considered after pipeline
push and so only for compaction. Now with this patch we are in sync. Tests
pass.
> Compacting Memstore : unnecessary push of active segments to pipeline
> ---------------------------------------------------------------------
>
> Key: HBASE-16162
> URL: https://issues.apache.org/jira/browse/HBASE-16162
> Project: HBase
> Issue Type: Sub-task
> Reporter: Anoop Sam John
> Assignee: Anoop Sam John
> Priority: Critical
> Attachments: HBASE-16162.patch, HBASE-16162_V2.patch,
> HBASE-16162_V3.patch, HBASE-16162_V4.patch
>
>
> We have flow like this
> {code}
> protected void checkActiveSize() {
> if (shouldFlushInMemory()) {
> InMemoryFlushRunnable runnable = new InMemoryFlushRunnable();
> }
> getPool().execute(runnable);
> }
> }
> private boolean shouldFlushInMemory() {
> if(getActive().getSize() > inmemoryFlushSize) {
> // size above flush threshold
> return (allowCompaction.get() && !inMemoryFlushInProgress.get());
> }
> return false;
> }
> void flushInMemory() throws IOException {
> // Phase I: Update the pipeline
> getRegionServices().blockUpdates();
> try {
> MutableSegment active = getActive();
> pushActiveToPipeline(active);
> } finally {
> getRegionServices().unblockUpdates();
> }
> // Phase II: Compact the pipeline
> try {
> if (allowCompaction.get() &&
> inMemoryFlushInProgress.compareAndSet(false, true)) {
> // setting the inMemoryFlushInProgress flag again for the case this
> method is invoked
> // directly (only in tests) in the common path setting from true to
> true is idempotent
> // Speculative compaction execution, may be interrupted if flush is
> forced while
> // compaction is in progress
> compactor.startCompaction();
> }
> {code}
> So every write of cell will produce the check checkActiveSize(). When we
> are at border of in mem flush, many threads doing writes to this memstore
> can get this checkActiveSize () to pass. Yes the AtomicBoolean is still
> false only. It is turned ON after some time once the new thread is started
> run and it push the active to pipeline etc.
> In the new thread code of inMemFlush, we dont have any size check. It just
> takes the active segment and pushes that to pipeline. Yes we dont allow any
> new writes to memstore at this time. But before that write lock on
> region, other handler thread also might have added entry to this thread pool.
> When the 1st one finishes, it releases the lock on region and handler
> threads trying for write to memstore, might get lock and add some data. Now
> this 2nd in mem flush thread may get a chance and get the lock and so it just
> takes current active segment and flush that in memory ! This will produce
> very small sized segments to pipeline.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
