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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12728) buffered writes substantially less useful after removal of HTablePool
Date Wed, 21 Jan 2015 02:54:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14285069#comment-14285069
] 

Hadoop QA commented on HBASE-12728:
-----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12693458/HBASE-12728-4.patch
  against master branch at commit 9bdb81f0a1db308a8a452379455b6bbfe70ea20d.
  ATTACHMENT ID: 12693458

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:green}+1 tests included{color}.  The patch appears to include 99 new or modified
tests.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:red}-1 javadoc{color}.  The javadoc tool appears to have generated 2 warning messages.

    {color:green}+1 checkstyle{color}.  The applied patch does not increase the total number
of checkstyle errors

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version
2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines longer than 100

  {color:green}+1 site{color}.  The mvn site goal succeeds with this patch.

    {color:green}+1 core tests{color}.  The patch passed unit tests in .

Test results: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-protocol.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-thrift.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-hadoop2-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-rest.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-examples.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-client.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-prefix-tree.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/newPatchFindbugsWarningshbase-annotations.html
Checkstyle Errors: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/checkstyle-aggregate.html

  Javadoc warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//artifact/patchprocess/patchJavadocWarnings.txt
Console output: https://builds.apache.org/job/PreCommit-HBASE-Build/12523//console

This message is automatically generated.

> buffered writes substantially less useful after removal of HTablePool
> ---------------------------------------------------------------------
>
>                 Key: HBASE-12728
>                 URL: https://issues.apache.org/jira/browse/HBASE-12728
>             Project: HBase
>          Issue Type: Bug
>          Components: hbase
>    Affects Versions: 0.98.0
>            Reporter: Aaron Beppu
>            Assignee: Nick Dimiduk
>            Priority: Blocker
>             Fix For: 1.0.0, 2.0.0, 1.1.0
>
>         Attachments: 12728.connection-owns-buffers.example.branch-1.0.patch, HBASE-12728-2.patch,
HBASE-12728-3.patch, HBASE-12728-4.patch, HBASE-12728.patch, bulk-mutator.patch
>
>
> In previous versions of HBase, when use of HTablePool was encouraged, HTable instances
were long-lived in that pool, and for that reason, if autoFlush was set to false, the table
instance could accumulate a full buffer of writes before a flush was triggered. Writes from
the client to the cluster could then be substantially larger and less frequent than without
buffering.
> However, when HTablePool was deprecated, the primary justification seems to have been
that creating HTable instances is cheap, so long as the connection and executor service being
passed to it are pre-provided. A use pattern was encouraged where users should create a new
HTable instance for every operation, using an existing connection and executor service, and
then close the table. In this pattern, buffered writes are substantially less useful; writes
are as small and as frequent as they would have been with autoflush=true, except the synchronous
write is moved from the operation itself to the table close call which immediately follows.
> More concretely :
> ```
> // Given these two helpers ...
> private HTableInterface getAutoFlushTable(String tableName) throws IOException {
>   // (autoflush is true by default)
>   return storedConnection.getTable(tableName, executorService);
> }
> private HTableInterface getBufferedTable(String tableName) throws IOException {
>   HTableInterface table = getAutoFlushTable(tableName);
>   table.setAutoFlush(false);
>   return table;
> }
> // it's my contention that these two methods would behave almost identically,
> // except the first will hit a synchronous flush during the put call,
> and the second will
> // flush during the (hidden) close call on table.
> private void writeAutoFlushed(Put somePut) throws IOException {
>   try (HTableInterface table = getAutoFlushTable(tableName)) {
>     table.put(somePut); // will do synchronous flush
>   }
> }
> private void writeBuffered(Put somePut) throws IOException {
>   try (HTableInterface table = getBufferedTable(tableName)) {
>     table.put(somePut);
>   } // auto-close will trigger synchronous flush
> }
> ```
> For buffered writes to actually provide a performance benefit to users, one of two things
must happen:
> - The writeBuffer itself shouldn't live, flush and die with the lifecycle of it's HTableInstance.
If the writeBuffer were managed elsewhere and had a long lifespan, this could cease to be
an issue. However, if the same writeBuffer is appended to by multiple tables, then some additional
concurrency control will be needed around it.
> - Alternatively, there should be some pattern for having long-lived HTable instances.
However, since HTable is not thread-safe, we'd need multiple instances, and a mechanism for
leasing them out safely -- which sure sounds a lot like the old HTablePool to me.
> See discussion on mailing list here : http://mail-archives.apache.org/mod_mbox/hbase-user/201412.mbox/%3CCAPdJLkEzmUQZ_kvD%3D8mrxi4V%3DhCmUp3g9MUZsddD%2Bmon%2BAvNtg%40mail.gmail.com%3E



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