You could keep track of which nodes are ephemeral by looking at the stat object passed to the NODE_ADDED event in the TreeCache. Then when you get a NODE_REMOVED event you could check if it's one of your ephemeral nodes?
On Thu, Oct 15, 2015 at 4:06 AM, Vikrant Singh <[email protected]> wrote: > 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 <[email protected]> > 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 < >> [email protected]> 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 <[email protected]> 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:[email protected]] >>>> *Sent:* Monday, October 12, 2015 5:05 PM >>>> *To:* [email protected] >>>> *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 < >>>> [email protected]> 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 >>>> >>>> >>>> >>> >>> >> >
