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From Benjamin Reed <br...@yahoo-inc.com>
Subject Re: closing session on socket close vs waiting for timeout
Date Mon, 06 Sep 2010 21:10:57 GMT
if this mechanism were used very often, we would get a huge number of 
session expirations when a server fails. you are trading fast error 
detection for the ability to tolerate temporary network and server outages.

to be honest this seems like something that in theory sounds like it 
will work in practice, but once deployed we start getting session 
expirations for cases that we really do not want or expect.


On 09/01/2010 12:47 PM, Patrick Hunt wrote:
> Ben, in this case the session would be tied directly to the connection,
> we'd explicitly deny session re-establishment for this session type (so
> 4 would fail). Would that address your concern, others?
> Patrick
> On 09/01/2010 10:03 AM, Benjamin Reed wrote:
>> i'm a bit skeptical that this is going to work out properly. a server
>> may receive a socket reset even though the client is still alive:
>> 1) client sends a request to a server
>> 2) client is partitioned from the server
>> 3) server starts trying to send response
>> 4) client reconnects to a different server
>> 5) partition heals
>> 6) server gets a reset from client
>> at step 6 i don't think you want to delete the ephemeral nodes.
>> ben
>> On 08/31/2010 01:41 PM, Fournier, Camille F. [Tech] wrote:
>>> Yes that's right. Which network issues can cause the socket to close
>>> without the initiating process closing the socket? In my limited
>>> experience in this area network issues were more prone to leave dead
>>> sockets open rather than vice versa so I don't know what to look out for.
>>> Thanks,
>>> Camille
>>> -----Original Message-----
>>> From: Dave Wright [mailto:wrightd@gmail.com]
>>> Sent: Tuesday, August 31, 2010 1:14 PM
>>> To: zookeeper-user@hadoop.apache.org
>>> Subject: Re: closing session on socket close vs waiting for timeout
>>> I think he's saying that if the socket closes because of a crash (i.e.
>>> not a
>>> normal zookeeper close request) then the session stays alive until the
>>> session timeout, which is of course true since ZK allows reconnection and
>>> resumption of the session in case of disconnect due to network issues.
>>> -Dave Wright
>>> On Tue, Aug 31, 2010 at 1:03 PM, Ted Dunning<ted.dunning@gmail.com>
>>> wrote:
>>>> That doesn't sound right to me.
>>>> Is there a Zookeeper expert in the house?
>>>> On Tue, Aug 31, 2010 at 8:58 AM, Fournier, Camille F. [Tech]<
>>>> Camille.Fournier@gs.com>  wrote:
>>>>> I foolishly did not investigate the ZK code closely enough and it seems
>>>>> that closing the socket still waits for the session timeout to
>>>>> remove the
>>>>> session.

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