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From: kamel.zaarouri@gmail.com
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Subject: Re: out of order callbacks of events in ZK
Message-Id: <A197273E-D337-4CED-8F0D-0EB95847EC3C@gmail.com>
Date: Fri, 6 Nov 2015 15:50:16 -0500
References: 
 <CAFau7Xe_u+MoNK+ugWowTCtAz1eyhi0xw+i4YPgdc1uYNYi9Jw@mail.gmail.com>
 <D2624FFD.31FD0%cnauroth@hortonworks.com>
In-Reply-To: <D2624FFD.31FD0%cnauroth@hortonworks.com>
To: user@zookeeper.apache.org

Thanks you for your reply.

In that case is there a standard solution to synchronize different clients?=20=

If ordered changes to ZK might be seen out of order with certain clients, th=
en what is the standard way to synchronize clients?


> On Nov 6, 2015, at 3:41 PM, Chris Nauroth <cnauroth@hortonworks.com> wrote=
:
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> Hello Kamel,
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> The behavior you're seeing is not at odds with ZooKeeper's guarantees.
> For more details, please refer to the ZooKeeper programmer's guide
> statements on consistency guarantees.
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> http://zookeeper.apache.org/doc/r3.4.6/zookeeperProgrammers.html#ch_zkGuar=
a
> ntees
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> In particularly, note the sidebar describing how ZooKeeper does not
> guarantee simultaneously consistent cross-client views.
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> --Chris Nauroth
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>=20
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>> On 11/6/15, 12:32 PM, "kamel zaarouri" <kamel.zaarouri@gmail.com> wrote:
>>=20
>> Hi zk-users,
>>=20
>> Assume this tree:
>>=20
>>=20
>> parent1
>> |         |____Child1
>> |
>> |
>> parent2
>>        |_____<empty>
>>=20
>>=20
>> I have 1 watchers on parent1 and another watcher on parent2. I have those=

>> watchers setup to receive updates of the child nodes of both parents.
>>=20
>> Child1 is a non-ephemeral node.
>>=20
>> If another client:
>>=20
>> - Creates an ephemeral node (let's call it ephem2) under parent2
>> then and only then it
>> - Updates Child1
>>=20
>> What I am seeing now is that 20% of the time, I receive the callbacks out=

>> of order, i.e. I see the Child1 being updated before ephem2 is seen
>> created.
>>=20
>> Is this is a bug in the client I am using or does ZK not guarantee order
>> in
>> this way?
>>=20
>> Thank you!,
>=20