[
https://issues.apache.org/jira/browse/MAPREDUCE-6237?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14304363#comment-14304363
]
Hadoop QA commented on MAPREDUCE-6237:
--------------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12696317/mapreduce-6237.patch
against trunk revision b73e776.
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. There were no new javadoc warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:red}-1 findbugs{color}. The patch appears to introduce 13 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 core tests{color}. The patch passed unit tests in
hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/5149//testReport/
Findbugs warnings:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/5149//artifact/patchprocess/newPatchFindbugsWarningshadoop-mapreduce-client-core.html
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/5149//console
This message is automatically generated.
> DBRecordReader is not thread safe
> ---------------------------------
>
> Key: MAPREDUCE-6237
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6237
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 2.5.0
> Reporter: Kannan Rajah
> Assignee: Kannan Rajah
> Attachments: mapreduce-6237.patch, mapreduce-6237.patch
>
>
> DBInputFormat.createDBRecorder is reusing JDBC connections across instances
> of DBRecordReader. This is not a good idea. We should be creating separate
> connection. If performance is a concern, then we should be using connection
> pooling instead.
> I looked at DBOutputFormat.getRecordReader. It actually creates a new
> Connection object for each DBRecordReader. So can we just change
> DBInputFormat to create new Connection every time? The connection reuse code
> was added as part of connection leak bug in MAPREDUCE-1443. Any reason for
> caching the connection?
> We observed this issue in a customer setup where they were reading data from
> MySQL using Pig. As per customer, the query is returning two records which
> causes Pig to create two instances of DBRecordReader. These two instances are
> sharing the database connection instance. The first DBRecordReader runs to
> extract the first record from MySQL just fine, but then closes the shared
> connection instance. When the second DBRecordReader runs, it tries to execute
> a query to retrieve the second record on the closed shared connection
> instance, which fail. If we set
> mapred.map.tasks to 1, the query will be successful.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
