[jira] [Commented] (ZOOKEEPER-2107) zookeeper client should support custom HostProviders

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

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14288962#comment-14288962 ] 

Hadoop QA commented on ZOOKEEPER-2107:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12694103/enable-custom-hostprovider_in_zookeeper-client.patch
  against trunk revision 1646992.

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

    -1 tests included.  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.

    -1 javadoc.  The javadoc tool appears to have generated 4 warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler 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 passed core unit tests.

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

Test results: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2485//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2485//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/2485//console

This message is automatically generated.

> zookeeper client should support custom HostProviders
> ----------------------------------------------------
>
>                 Key: ZOOKEEPER-2107
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2107
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: java client
>    Affects Versions: 3.5.0
>            Reporter: Robert Kamphuis
>             Fix For: 3.5.1
>
>         Attachments: enable-custom-hostprovider_in_zookeeper-client.patch
>
>
> The zookeeper client currently contains a StaticHostProvider and no means to replace it with your own implementation of the existing HostProvider interface. It would be great if the zookeeper client would enable you to create an instance with your own implementation of the HostProvider interface. 
> We have been testing this change with our implementation of HostProvider which does the name to ip lookup at the time of finding the next() server to connect to. In our AWS based deployments, this enables that applications can actually connect to swapped out zookeeper-servers which typically get a new ip address. With the current StaticHostProvider in practice you will need to restart the application to see the replaced zookeeper as the application continues to try to connect to the old no longer existing IP address. 
> With this little change plus a straightforward implementation of the HostProvider interface (our LateResolvingHostProvider), we can replace the zookeeper servers one at a time, re-assigning the elastic ips we use for the zookeeper servers, and have the application servers re-connect to the zookeeper cluster including the replaced ones without any downtime and without having to rely on the elastic ips for client to zookeeper-server connections. The reason for not using elastic-ips in the connect-strings but use the names which map to the (changing) private ips is to be able to rely on security-groups to control access. 
> While this seems very specific for AWS, this anyway seems a generic improvement for other deployments where the mapping from server name to IP address is not static. 



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