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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: Curator PathChildrenCache sends delete events but no delete happened
Date Tue, 25 Oct 2016 18:25:35 GMT
Multiple reports now. Can someone open an issue? Let’s try to figure out what’s happening.

-JZ

> On Oct 25, 2016, at 1:19 PM, Benjamin Jaton <benjamin.jaton@gmail.com> wrote:
> 
> Hi Curtis, thanks for the feedback.
> Do you know if there is a JIRA associated to this?
> I also use PathChildrenCache to do deletions on the file system. May I ask how you mitigated
the issue?
> 
> On Tue, Oct 25, 2016 at 6:17 AM, Cantrell, Curtis <Curtis.Cantrell@bkfs.com <mailto:Curtis.Cantrell@bkfs.com>>
wrote:
> I have also experienced 3 delete events in the last year when there were no actual deletes
in ZK.   I was using the delete events as a trigger to do an actual deletion in the system.
 Since we experienced false deletes, I had to rethink the way I was using the PathChildrenCache.
> 
>  
> 
> Thank you,
> 
> Curtis Cantrell
> 
>  
> 
>  
> 
> From: Benjamin Jaton [mailto:benjamin.jaton@gmail.com <mailto:benjamin.jaton@gmail.com>]

> Sent: Monday, October 24, 2016 7:34 PM
> To: user@curator.apache.org <mailto:user@curator.apache.org>
> Subject: Re: Curator PathChildrenCache sends delete events but no delete happened
> 
>  
> 
> Hi Cameron, thanks for your answer.
> 
> Yes I noticed that too, it seems to be coming from the ZK client layer.
> I have tried to use the ZK Watcher API but I couldn't reproduce the issue when I was
using them.
> 
> I will have a look at how PathChildrenCache does it and keep you posted.
> 
> Thanks
> 
> Benjamin
> 
>  
> 
> On Mon, Oct 24, 2016 at 4:08 PM, Cameron McKenzie <mckenzie.cam@gmail.com <mailto:mckenzie.cam@gmail.com>>
wrote:
> 
> hey Benjamin,
> 
> I'm not aware of any such edge cases, but that does not mean that they don't exist. From
the log: 
> 
>  
> 
> 2016-10-24 15:52:43 DEBUG o.a.z.ClientCnxn:889 - Got WatchedEvent state:SyncConnected
type:NodeDeleted path:/benji2/123 for sessionid 0x20014cf3d480003
> 
>  
> 
> This is being logged by the Zookeeper client itself that Curator is using. So it doesn't
appear to be Curator inferring some sort of delete event. It looks like an explicit watched
event coming from Zookeeper.
> 
>  
> 
> cheers
> 
>  
> 
> On Tue, Oct 25, 2016 at 10:04 AM, Benjamin Jaton <benjamin.jaton@gmail.com <mailto:benjamin.jaton@gmail.com>>
wrote:
> 
> Hello,
> 
> I am using PathChildrenCache and I am receiving delete events even if there is no actual
delete in ZK. I printed the WatchedEvent details for 2 of those delete events (of the same
node /benji2/123) I received in the same JVM run:
> 
> 
> 
> 2016-10-24 15:52:43 DEBUG o.a.z.ClientCnxn:889 - Got WatchedEvent state:SyncConnected
type:NodeDeleted path:/benji2/123 for sessionid 0x20014cf3d480003
> [PathChildrenCacheListener] delete event for /benji2/123
> PathChildrenCacheEvent{type=CHILD_REMOVED, data=ChildData{path='/benji2/123', stat=19808389169191,19808389169191,1477335789916,1477335789916,0,0,0,0,0,0,19808389169191
> , data=[]}}
> null
> ChildData{path='/benji2/123', stat=19808389169191,19808389169191,1477335789916,1477335789916,0,0,0,0,0,0,19808389169191
> , data=[]}
> getAversion=0
> 2016-10-24 15:52:43 DEBUG o.a.z.ClientCnxn:867 - Got notification sessionid:0x20014cf3d480003
> getCtime=1477335789916
> getCversion=0
> getCzxid=19808389169191
> getMtime=1477335789916
> 2016-10-24 15:52:43 DEBUG o.a.z.ClientCnxn:889 - Got WatchedEvent state:SyncConnected
type:NodeDeleted path:/benji2 for sessionid 0x20014cf3d480003
> getMzxid=19808389169191
> getPzxid=19808389169191
> getVersion=0
> 
> (...)
> 
> 2016-10-24 15:58:06 DEBUG o.a.z.ClientCnxn:889 - Got WatchedEvent state:SyncConnected
type:NodeDeleted path:/benji2/123 for sessionid 0x20014cf3d480003
> [PathChildrenCacheListener] delete event for /benji2/123
> PathChildrenCacheEvent{type=CHILD_REMOVED, data=ChildData{path='/benji2/123', stat=19808389169191,19808389169191,1477335789916,1477335789916,0,0,0,0,0,0,19808389169191
> , data=[]}}
> null
> 2016-10-24 15:58:06 DEBUG o.a.z.ClientCnxn:867 - Got notification sessionid:0x20014cf3d480003
> ChildData{path='/benji2/123', stat=19808389169191,19808389169191,1477335789916,1477335789916,0,0,0,0,0,0,19808389169191
> , data=[]}
> getAversion=0
> getCtime=1477335789916
> getCversion=0
> getCzxid=19808389169191
> getMtime=1477335789916
> getMzxid=19808389169191
> getPzxid=19808389169191
> getVersion=0
> 
> 
> Are there known edge cases where this can happen? Again there is no delete at all in
ZK, I verified the transaction log of ZooKeeper, no delete is present).
> 
> Thanks,
> 
> Benjamin
> 
>  
> 
>  
> 
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