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Date: Fri, 2 Oct 2015 10:06:58 -0700
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 <CABzk7oo3j0-t9KjFajFBFcriHYe+BEs2kp1yrjrQwpdtYTxafg@mail.gmail.com>
Subject: Re: Can a CRUD operation succeed when we have a
 ConnectionLossException?
From: Benjamin Jaton <bjaton@radiantlogic.com>
To: user@zookeeper.apache.org
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Thank you, I appreciate the feedback.

On Fri, Oct 2, 2015 at 10:01 AM, Ra=C3=BAl Guti=C3=A9rrez Segal=C3=A9s <rgs=
@itevenworks.net
> wrote:

> On 2 October 2015 at 09:48, Benjamin Jaton <benjamin.jaton@gmail.com>
> wrote:
>
> > Hi,
> >
> > In a small test class I keep creating/deleting the same node /test.
> >
> > I kill (Ctrl+C) and restart the ZK server in the command line randomly.
> >
> > After a couple attempts here is what we get:
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > *Fri Oct 02 09:27:23 PDT 2015 - Deleting /testFri Oct 02 09:27:23 PDT
> 2015
> > - /test has been deleted.Fri Oct 02 09:27:23 PDT 2015 - Node /test has
> > successfully been removed.Fri Oct 02 09:27:23 PDT 2015 - Recreating
> > /testFri Oct 02 09:27:23 PDT 2015 - CONN LOST on createFri Oct 02
> 09:27:24
> > PDT 2015 - ERROR: node should be removed.Fri Oct 02 09:27:24 PDT 2015 -
> > Data of node is: testNode has been mysteriously
> > created...org.apache.zookeeper.KeeperException$NodeExistsException:
> > KeeperErrorCode =3D NodeExists for /test    at
> > org.apache.zookeeper.KeeperException.create(KeeperException.java:123)
> at
> > org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
> at
> > org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:1209)    at
> > TestZKSaveConnLoss.create(TestZKSaveConnLoss.java:101)    at
> > TestZKSaveConnLoss.access$4(TestZKSaveConnLoss.java:98)    at
> > TestZKSaveConnLoss$2.run(TestZKSaveConnLoss.java:56)*
> >
> > The 1st create fails with a ConnectionLossException.
> > When we retry to create the node, we get a NodeExistsException.
> >
> > So the node got created despite the ConnectionLossException.
> > The same thing happens with the delete operation.
> >
> > I was wondering if this is an known/expected behavior and how people de=
al
> > with it?
> >
>
> It's totally legit. Say you have:
>
> client> sends create /foo
> server> receives receives requests and fwds to the leader
> server> is about to reply that the create happened
> ... RSTs are injected and socket goes away ...
> client> sees ConnectionLoss
>
> The way the client would deal with this is by calling exists() on the nod=
es
> it cares about, after recovering
> from ConnectionLoss.
>
>
> -rgs
>

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