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From "Bae, Jae Hyeon" <metac...@gmail.com>
Subject Re: how to properly recreate ephemeral nodes and reset watches after a session expiry
Date Thu, 14 Nov 2013 07:17:00 GMT
When the connection state is changed to RECONNECTED,
PersistentEphemeralNode is retrying to create the node and set the watcher.


On Wed, Nov 13, 2013 at 10:47 PM, Senecal, Shaun | Shaun | BDD <
shaun.senecal@mail.rakuten.com> wrote:

>  How does this work if the connection to ZK is lost for an extended
> period of time?  Depending on your retry behaviour, it appears to give up
> retrying before the connection is re-established and the watch isn't set.
> I can't see how PersistentEphemeralNode is handling this situation, is
> there some trick I am missing?
>
>
> Shaun
>
>  ------------------------------
> *From:* Jordan Zimmerman [jordan@jordanzimmerman.com]
> *Sent:* Wednesday, November 13, 2013 12:16 AM
> *To:* user@curator.apache.org
> *Subject:* Re: how to properly recreate ephemeral nodes and reset watches
> after a session expiry
>
>   Have a look at PersistentEphemeralNode. It does this.
>
>  -Jordan
>
>  On Nov 11, 2013, at 11:20 PM, Senecal, Shaun | Shaun | BDD <
> shaun.senecal@mail.rakuten.com> wrote:
>
>  Hi,
>
> I have some code that needs to be able to recreate ephemeral nodes and
> reset watches after a session expiry.  The approach currently taken is to
> keep track of all nodes that need to be recreated and all watches that need
> to be reset, then use a ConnectionStateListener to trigger the recovery
> process when a RECONNECTED event is received after a LOST event.  It has
> been a painful process getting this to work, because I want the logic to be
> able to survive issues that occur DURING the recovery process as well.
>
> While the current implementation seems to be working, I'm left feeling
> that there has to be a better way to do this.  What is the "best practice"
> approach?
>
> I came across this link (
> https://listserv.netflix.com/pipermail/curator-users/2012-June/000068.html)
> implying that you shouldn't recreate ephemeral nodes in a
> ConnectionStateListener, and instead should add a watch to each node which
> recreates the node when NodeDeleted or Expired is received.  I have tested
> this solution and it appears to work.  The only place I see this method
> getting really complicated is if I need to set watches (ie getData()) on
> ephemeral nodes which I want to be reset after an expiry since I would need
> to worry about ensuring the ephemeral node is recreated before attempting
> to reset the watch.  Is this considered the best practice?
>
>
>
> Thanks,
>
> Shaun
>
>
>

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