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https://issues.apache.org/jira/browse/HDFS-7858?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14344311#comment-14344311
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Hadoop QA commented on HDFS-7858:
---------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12701992/HDFS-7858.1.patch
against trunk revision ca1c00b.
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 3 new
or modified test files.
{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 4 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-common-project/hadoop-common hadoop-hdfs-project/hadoop-hdfs
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common:
org.apache.hadoop.hdfs.server.namenode.TestNameNodeRetryCacheMetrics
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/9699//testReport/
Findbugs warnings:
https://builds.apache.org/job/PreCommit-HDFS-Build/9699//artifact/patchprocess/newPatchFindbugsWarningshadoop-hdfs.html
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/9699//console
This message is automatically generated.
> Improve HA Namenode Failover detection on the client
> ----------------------------------------------------
>
> Key: HDFS-7858
> URL: https://issues.apache.org/jira/browse/HDFS-7858
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Arun Suresh
> Assignee: Arun Suresh
> Attachments: HDFS-7858.1.patch
>
>
> In an HA deployment, Clients are configured with the hostnames of both the
> Active and Standby Namenodes.Clients will first try one of the NNs
> (non-deterministically) and if its a standby NN, then it will respond to the
> client to retry the request on the other Namenode.
> If the client happens to talks to the Standby first, and the standby is
> undergoing some GC / is busy, then those clients might not get a response
> soon enough to try the other NN.
> Proposed Approach to solve this :
> 1) Since Zookeeper is already used as the failover controller, the clients
> could talk to ZK and find out which is the active namenode before contacting
> it.
> 2) Long-lived DFSClients would have a ZK watch configured which fires when
> there is a failover so they do not have to query ZK everytime to find out the
> active NN
> 2) Clients can also cache the last active NN in the user's home directory
> (~/.lastNN) so that short-lived clients can try that Namenode first before
> querying ZK
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