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From Moshiko Kasirer <mos...@liveperson.com>
Subject Re: question about curator - retry policy
Date Fri, 20 May 2016 22:07:28 GMT
I mean that while zk cluster is up the curator connection state stays LOST
Which in our case means the app node in which it happens doesnt register
himself as avalable.... I just don't seem to understand when does curator
gives up on trying to connect zk and when he doesn't give up.
Thanks for the help !
בתאריך 21 במאי 2016 00:58,‏ "Jordan Zimmerman" <jordan@jordanzimmerman.com>
כתב:

> You must have a retry policy so that you don’t overwhelm your network and
> ZooKeeper cluster. The example code shows how to create a reasonable one.
>
> sometimes although zk cluster is up the curator service discovery
> connection isn't
>
> Service Discovery’s internal instances might be waiting based on the retry
> policy. But, what do you mean by "curator service discovery connection
> isn’t”? There isn’t such a thing as a service discovery connection.
>
> -Jordan
>
> On May 20, 2016, at 4:53 PM, Moshiko Kasirer <moshek@liveperson.com>
> wrote:
>
> We are using your service discovery. So you are saying I should not care
> about the retry policy...? So the only thing left to explain is how come
> sometimes although zk cluster is up the curator service discovery
> connection isn't.....
> בתאריך 21 במאי 2016 00:43,‏ "Jordan Zimmerman" <jordan@jordanzimmerman.com>
> כתב:
>
> If you are using Curator’s Service Discovery code, it will be continuously
> re-trying the connections. This is not because of the retry policy it’s
> because the Service Discovery code manages connection interruptions
> internally.
>
> -Jordan
>
> On May 20, 2016, at 4:40 PM, Moshiko Kasirer <moshek@liveperson.com>
> wrote:
>
> Thanks for the replay I will send those logs ASAP.
> It's difficult to understand the connection mechanism of zk ....
> We are using curator 2.10 as our service discovery so we have to make sure
> that when zk is alive we connect and inform the our server is up we do that
> by listening to curator connection listener which I think has also to do
> with the retry policy.... But what I can't understand is why sometimes we
> can see in the log that curator gave up (Lost) yet still a second later
> curator connection is restored how? Is it because zk session heartbeat
> restored the connection? Does that Iovine curator to change his connection
> state? And on the other side we sometimes get to a point were zk is up but
> curator connection stays as Lost...
> That is why I thought of using the new always try policy you entered do
> you think it can help? That why  hope there will be no way that zk is up
> but curator status is lost.....as once he will retry he will reconnect to
> zk.... Is that correct?
> בתאריך 21 במאי 2016 00:10,‏ "Jordan Zimmerman" <jordan@jordanzimmerman.com>
> כתב:
>
>> Curator’s retry policies are used within each CuratorFramework operation.
>> For example, when you call client.setData().forPath(p, b) the retry policy
>> will be invoked if there is a retry-able exception during the operation. In
>> addition to the retryPolicy, there are connection timeouts. The behavior of
>> how this is handled changed between Curator 2.x and Curator 3.x. In Curator
>> 2.x, for every iteration of the retry, the operation will wait until
>> connection timeout when there’s no connection. In Curator 3.x, the
>> connection timeout wait only occurs once (if the default
>> ConnectionHandlingPolicy is used).
>>
>> In any event, ZooKeeper itself tries to maintain the connection. Also,
>> Curator will re-create the internally managed connection depending various
>> network interruptions, etc. I’d need to see the logs to give you more
>> input.
>>
>> -Jordan
>>
>> On May 19, 2016, at 10:12 AM, Moshiko Kasirer <moshek@liveperson.com>
>> wrote:
>>
>> first i would like to thank you about curator we are using it as part of
>> our service discovery
>>
>> solution and it helps a lot!!
>>
>> i have a question i hope you will be able to help me with.
>>
>> its regarding the curator retry policy it seems to me we dont really
>> understand when this policy is
>>
>> invoked,  as i see in our logs that although i configured it as max retry
>> 1 actually in the logs i see
>>
>> many ZK re connection attempts (and many curator gave up messages but
>> later i see
>>
>> reconnected status...) . is it possible that that policy is only relevant
>> to manually invoked
>>
>> operations against the ZK cluster done via curator ? and that the re
>> connections i see in the logs
>>
>> are caused by the fact that the ZK was available during start up so
>> sessions were created and
>>
>> then when ZK was down the ZK clients *(not curator) * are sending
>> heartbeats as part of the ZK
>>
>> architecture? that is the part i am failing to understand and i hope you
>> can help me with that.
>>
>> you have recently added RetreyAllways policy and i wanted to know if it
>> is save to use it?
>>
>> the thing is we always want to retry to reconnect to ZK when he is
>> available but that is something
>>
>> the ZK client does as long as he has open sessions right?  i am not sure
>> that it has to do with the
>>
>> retry policy ...
>>
>> thanks,
>>
>> moshiko
>>
>> --
>> Moshiko Kasirer
>> Software Engineer
>> T: +972-74-700-4357
>> <http://www.linkedin.com/company/164748> <http://twitter.com/liveperson>
>> <http://www.facebook.com/LivePersonInc> We Create Meaningful Connections
>> <http://roia.biz/im/n/ndiXvq1BAAGhL0MAABW7QgABwExmMQA-A/>
>>
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>>
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