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From Germán Blanco (JIRA) <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1808) Add version to FLE notifications for 3.4 branch
Date Fri, 08 Nov 2013 09:57:20 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13817159#comment-13817159
] 

Germán Blanco commented on ZOOKEEPER-1808:
------------------------------------------

This looks quite good, but I think that there is a problem with backwards compatibility.
Looking at the previous code (without this patch applied), the Notification will only be processed
correctly if the length is either 28 or less than 28. But we will be sending one of length
32 when adding the version.
Still, it seems that the message from an updated server will be processed by a server that
is not updated if we place the version in the last position of the message (it is now the
first thing that gets sent). Messages will be processed as backCompatibility=true (epoch will
be extracted from the zxid), but there will be no log of "Got a short response" (since it
is actually longer, that is ok).
This comparison "if(response.buffer.capacity() == 40) {" would be better as "if(response.buffer.capacity()
>= 40) {". We want the servers to be able to process notifications with more information
(from future updates), even if they just use the information that they know about and ignore
the rest.

> Add version to FLE notifications for 3.4 branch
> -----------------------------------------------
>
>                 Key: ZOOKEEPER-1808
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1808
>             Project: ZooKeeper
>          Issue Type: Sub-task
>            Reporter: Flavio Junqueira
>            Assignee: Flavio Junqueira
>             Fix For: 3.4.6
>
>         Attachments: ZOOKEEPER-1808.patch, ZOOKEEPER-1808.patch
>
>
> Add version to notification messages so that we can differentiate messages during rolling
upgrades. This task is for the 3.4 branch only. 



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