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From David Kesler <DKes...@yodle.com>
Subject RE: Persistent Ephemeral Node
Date Mon, 12 Oct 2015 21:33:04 GMT
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<mailto: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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