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From Vikrant Singh <vikrant.subscr...@gmail.com>
Subject Re: Persistent Ephemeral Node
Date Wed, 14 Oct 2015 17:06:12 GMT
yes you got it correct... a slight correction. I am trying to find a way
where I can make my tree cache event handler aware that "node removed"
event is coming from a persistent ephemeral node  and delay any action till
the point the node's curator framework gives up on rewriting the node to ZK.

On Mon, Oct 12, 2015 at 3:38 PM, Cameron McKenzie <mckenzie.cam@gmail.com>
wrote:

> So, if I'm understanding correctly, if your application loses its
> connection to ZooKeeper (or crashes), then a new instance will be started
> in its place, and if the original instance reconnects then you don't want
> it to try and recreate its ephemeral node?
>
> If that's the case, then I think that you need additional logic beyond
> what a PersistentEphemeralNode is going to provide you, as you will need to
> check if the node already exists on reconnection.
>
> On Tue, Oct 13, 2015 at 8:43 AM, Vikrant Singh <
> vikrant.subscribe@gmail.com> wrote:
>
>> yeah I considered that.. but I ended up using tree cache because it gives
>> me more control on the state of tree . I have some custom handlers for
>> add/remove/update events. Same cache is also used for service discovery.
>>
>> On Mon, Oct 12, 2015 at 2:33 PM, David Kesler <DKesler@yodle.com> wrote:
>>
>>> There’s also already a Curator service discovery extension library that
>>> you can look at:
>>> http://curator.apache.org/curator-x-discovery/index.html.  It’s
>>> basically boiling down to the same strategy of sticking an ephemeral node
>>> into ZK, but with some additional convenience and functionality built on
>>> top of it.
>>>
>>>
>>>
>>> *From:* Cameron McKenzie [mailto:mckenzie.cam@gmail.com]
>>> *Sent:* Monday, October 12, 2015 5:05 PM
>>> *To:* user@curator.apache.org
>>> *Subject:* Re: Persistent Ephemeral Node
>>>
>>>
>>>
>>> hey Vikrant,
>>>
>>> Using a persistent ephemeral node just means that your application code
>>> doesn't need to worry about handling recreation of the node when it
>>> reconnects to ZooKeeper after connection / session loss.
>>>
>>>
>>>
>>> If your ephemeral node should always be present whenever your
>>> application instance is running, then this would be a good use case for a
>>> persistent ephemeral node.
>>>
>>> cheers
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Oct 13, 2015 at 6:03 AM, Vikrant Singh <
>>> vikrant.subscribe@gmail.com> wrote:
>>>
>>> I have some basic question on persistent ephemeral node.
>>>
>>> Here is some background...
>>>
>>>
>>>
>>> We have a zoo keeper based service discovery setup. Each service
>>> register itself as a ephemeral node with zookeeper.When a service go down
>>>  its ephemeral node is removed from zookeeper and we know that service is
>>> down and we provision it again.
>>>
>>> At present we create plain ephemeral node. I am wondering what
>>> benefit/risks we may get if move to persistent ephemeral ones.  I see one
>>> problem... using  plane ephemeral node we can rely on state of ZK to make a
>>> decision like service is down. This is because we are sure that if a node
>>> get deleted with zoo keeper it will never comeback from same process. But
>>> if moved to "persistent ephemeral" I guess same may not be the case.
>>>
>>>
>>>
>>> Please let me know what you think of the same.
>>>
>>>
>>>
>>> Also I would like to know what are the best scenario where one should
>>> prefer using persistent ephemeral node over ephemeral node.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Vikrant
>>>
>>>
>>>
>>
>>
>

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