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https://issues.apache.org/jira/browse/ZOOKEEPER-1909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13964988#comment-13964988
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Rakesh R commented on ZOOKEEPER-1909:
-------------------------------------
Thanks [~rgs] for pointingout the usecase. Could you please clarify the
following:
I hope this is a kind of notification is "in flight", say just before
submitting the call to server, client recieves the watch notification. Now
otherside server will not be able to see the watch anymore. isn't it ?
In client side, we have two phase validation (1)before submitting the call to
server and (2)after recieving the response from server. Also we know in server
side it will ensure orderly exec. (2)After recieving the success response from
server, again client will be checking whether I can remove the requested
watcher. If yes, it continues with 'WatchRemoval' notification otherwise it
throws 'NoWatcherException' to the user.
In our case, since the client would have recieved the watch notification before
the success response and now the (2) validation would be able to throw
NoWatcherException, what do you say? Also, could you please tell me whether
you have observed this case in tests ?
> removeWatches doesn't return NOWATCHER when there is no watch set
> -----------------------------------------------------------------
>
> Key: ZOOKEEPER-1909
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1909
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.5.0
> Reporter: Raul Gutierrez Segales
> Fix For: 3.5.0
>
> Attachments: ZOOKEEPER-1909.patch
>
>
> ZOOKEEPER-442 introduced support for a new opcode: removeWatches. The way it
> was implemented though, implies that you need to check on the client side if
> a watch/watcher is set *before* you send your request to the server. If you
> don't, ZK will just swallow your request and won't return an error code if
> there isn't a watch set for that path.
> I noticed this whilst implementing removeWatches for Kazoo [1]. As mentioned,
> I guess it could be expected that clients should do the check on their side
> but I think that the correct thing would to have the server do the validation
> and return the error code accordingly as well.
> [~rakeshr], [~phunt]: thoughts?
> [1]
> https://github.com/rgs1/kazoo/commit/44ca48e975aeea3fd0664fe13136a72caf89e54f
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