[jira] [Commented] (ZOOKEEPER-2024) Major throughput improvement with mixed workloads

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2024?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14113949#comment-14113949 ] 

Hadoop QA commented on ZOOKEEPER-2024:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12664994/ZOOKEEPER-2024.patch
  against trunk revision 1620111.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 11 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    -1 javac.  The applied patch generated 3 javac compiler warnings (more than the trunk's current 2 warnings).

    +1 findbugs.  The patch does not introduce any new Findbugs (version 2.0.3) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2303//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2303//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2303//console

This message is automatically generated.

> Major throughput improvement with mixed workloads
> -------------------------------------------------
>
>                 Key: ZOOKEEPER-2024
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2024
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: quorum, server
>            Reporter: Kfir Lev-Ari
>         Attachments: ZOOKEEPER-2024.patch
>
>
> The patch is applied to the commit processor, and solves two problems:
> 1. Stalling - once the commit processor encounters a local write request, it stalls local processing of all sessions until it receives a commit of that request from the leader. 
> In mixed workloads, this severely hampers performance as it does not allow read-only sessions to proceed at faster speed than read-write ones.
> 2. Starvation - as long as there are read requests to process, older remote committed write requests are starved. 
> This occurs due to a bug fix (https://issues.apache.org/jira/browse/ZOOKEEPER-1505) that forces processing of local read requests before handling any committed write. The problem is only manifested under high local read load. 
> Our solution solves these two problems. It improves throughput in mixed workloads (in our tests, by up to 8x), and reduces latency, especially higher percentiles (i.e., slowest requests). 
> The main idea is to separate sessions that inherently need to stall in order to enforce order semantics, from ones that do not need to stall. To this end, we add data structures for buffering and managing pending requests of stalled sessions; these requests are moved out of the critical path to these data structures, allowing continued processing of unaffected sessions. 
> In order to avoid starvation, our solution prioritizes committed write requests over reads, and enforces fairness among read requests of sessions. 
> Please see the docs:  
> 1) https://docs.google.com/document/d/1oXJiSt9VqL35hCYQRmFuC63ETd0F_g6uApzocgkFe3Y/edit?usp=sharing - includes a detailed description of the new commit processor algorithm.
> 2) The attached patch implements our solution, and a collection of related unit tests
> 3) https://docs.google.com/spreadsheets/d/1vmdfsq4WLr92BQO-CGcualE0KhAtjIu3bCaVwYajLo8/edit?usp=sharing - shows performance results of running system tests on the patched ZK using the patched system test from https://issues.apache.org/jira/browse/ZOOKEEPER-2023. 
> See also https://issues.apache.org/jira/browse/ZOOKEEPER-1609



--
This message was sent by Atlassian JIRA
(v6.2#6252)