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https://issues.apache.org/jira/browse/HDFS-7300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14187957#comment-14187957
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Hadoop QA commented on HDFS-7300:
---------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12677770/HDFS-7300.v2.patch
against trunk revision 3f48493.
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 1 new
or modified test files.
{color:red}-1 javac{color}. The applied patch generated 1267 javac
compiler warnings (more than the trunk's current 1265 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: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:red}-1 core tests{color}. The patch failed these unit tests in
hadoop-hdfs-project/hadoop-hdfs:
org.apache.hadoop.hdfs.server.datanode.TestDataNodeMultipleRegistrations
org.apache.hadoop.hdfs.server.namenode.ha.TestFailureToReadEdits
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/8577//testReport/
Javac warnings:
https://builds.apache.org/job/PreCommit-HDFS-Build/8577//artifact/patchprocess/diffJavacWarnings.txt
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/8577//console
This message is automatically generated.
> The getMaxNodesPerRack() method in BlockPlacementPolicyDefault is flawed
> ------------------------------------------------------------------------
>
> Key: HDFS-7300
> URL: https://issues.apache.org/jira/browse/HDFS-7300
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Priority: Critical
> Attachments: HDFS-7300.patch, HDFS-7300.v2.patch
>
>
> The {{getMaxNodesPerRack()}} can produce an undesirable result in some cases.
> - Three replicas on two racks. The max is 3, so everything can go to one rack.
> - Two replicas on two or more racks. The max is 2, both replicas can end up
> in the same rack.
> {{BlockManager#isNeededReplication()}} fixes this after block/file is closed
> because {{blockHasEnoughRacks()}} will return fail. This is not only extra
> work, but also can break the favored nodes feature.
> When there are two racks and two favored nodes are specified in the same
> rack, NN may allocate the third replica on a node in the same rack, because
> {{maxNodesPerRack}} is 3. When closing the file, NN moves a block to the
> other rack. There is 66% chance that a favored node is moved. If
> {{maxNodesPerRack}} was 2, this would not happen.
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