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From Łukasz Osipiuk <luk...@osipiuk.net>
Subject Re: permanent ZSESSIONMOVED
Date Tue, 16 Mar 2010 18:51:30 GMT
On Tue, Mar 16, 2010 at 19:22, Patrick Hunt <phunt@apache.org> wrote:
> Łukasz Osipiuk wrote:
>>
>> On Tue, Mar 16, 2010 at 17:18, Patrick Hunt <phunt@apache.org> wrote:
>>>
>>> Can you verify that you are using 3.2.2 on all servers? You can do this
>>> by
>>> running the "stat" command against each of your servers and look at the
>>> very
>>> top of the output (we include the version of zk server there).
>>> http://bit.ly/dglVld
>>
>> Thanks for hint.
>>
>> We had 3.2.2 jars installed on all server - I checked it previously
>> but apparently our script which restarts instance
>> after installing .deb does not work very well and node2 and node3 were
>> running version 3.2.1.
>> Could using 3.2.1 be source of the problem?
>>
>
> I heard this story where customer service for dell asks customers to replug
> in the mouse because it might be "a dusty connection". Invariably when ppl
> look at the back of the box they find that the mouse is not actually plugged
> in. Brilliant ideas from CS perspective. ;-)
>
> I think that issue was fixed in 3.2.1, so I don't think that's an issue
> (version).

Damn :(

>>> Are you using synchronous or async operations in your client?
>>
>> We are only using async operations.
>
> Ok. good info.
>
>>
>>> I see snippets from the server logs, but I don't see anything from you
>>> client logs. It would really help if you could zip up all the logs
>>> (server
>>> and client) and provide them.
>>
>> We do not really have much logging on application side :(. Failed
>> operations are logged with error code (ZSESSIONEXPIRED in our case).
>> We also log session state changes but we noticed only changes between 1
>> and 3.
>> Unfortunately we do not have logs coming directly from zookeeper
>> library as it logs to stderr/stdout and we do not store any of them at
>> the moment.
>>
>
> I see, in this case I think that the log messages theyselves are the
> problem, ie we are warning about this, but it's not a real problem. We warn
> on things that we don't like but can handle, we error if we
> don'tlike/can'thandle.
>
> MOVED basically means that a client initiated a request on one server, then
> moved to another server before the request could be processed.
>
> In your case you are using async requests, that can actually make this
> problem show up more (more "in flight" requests vs sync operation).
>
> So if you are not seeing MOVED on the client then this is fine. If you see
> them in the server log it means what I said above.
>
> That make sense, or am I missing something?

It seems I was what I wrote was not clear. We are noticing errors on
client side. Any operation after
session gets into broken state fails with ZSESSIONMOVE error code (I
wrote ZSESSIONEXPIRED by mistake in previous post).
We get ZSESSIONMOVE from callback on rc parameter.

Session gets broken after zookeeper library reconnects to cluster,
although most of reconnection leave session if working state.

Regards, Łukasz


>
> Patrick
>
>
>
>> Regards, Łukasz
>>
>>> Patrick
>>>
>>> Łukasz Osipiuk wrote:
>>>>
>>>> not really - it happens occasionally - every few days :(
>>>> I believe it is somewhat connected with our network environment which
>>>> suffers from some packet loss which leads to
>>>> connection timeouts.
>>>>
>>>> I can switch on some more logging if you can lead me which categories
>>>> are worth to enable DEBUG for them.
>>>>
>>>> Regards, Łukasz Osipiuk
>>>>
>>>> On Tue, Mar 16, 2010 at 16:35, Benjamin Reed <breed@yahoo-inc.com>
>>>> wrote:
>>>>>
>>>>> weird, this does sound like a bug. do you have a reliable way of
>>>>> reproducing
>>>>> the problem?
>>>>>
>>>>> thanx
>>>>> ben
>>>>>
>>>>> On 03/16/2010 08:27 AM, Łukasz Osipiuk wrote:
>>>>>>
>>>>>> nope.
>>>>>>
>>>>>> I always pass 0 as clientid.
>>>>>>
>>>>>> Łukasz
>>>>>>
>>>>>> On Tue, Mar 16, 2010 at 16:20, Benjamin Reed<breed@yahoo-inc.com>
>>>>>>  wrote:
>>>>>>
>>>>>>> do you ever use zookeeper_init() with the clientid field set
to
>>>>>>> something
>>>>>>> other than null?
>>>>>>>
>>>>>>> ben
>>>>>>>
>>>>>>> On 03/16/2010 07:43 AM, Łukasz Osipiuk wrote:
>>>>>>>
>>>>>>>> Hi everyone!
>>>>>>>>
>>>>>>>> I am writing to this group because recently we are getting
some
>>>>>>>> strange errors with our production zookeeper setup.
>>>>>>>>
>>>>>>>>  From time to time we are observing that our client application
(C++
>>>>>>>> based) disconnects from zookeeper (session state is changed
to 1)
>>>>>>>> and
>>>>>>>> reconnects (state changed to 3).
>>>>>>>> This itself is not a problem - usually application continues
to run
>>>>>>>> without problems after reconnect.
>>>>>>>> But from time to time after above happens all subsequent
operations
>>>>>>>> start to return ZSESSIONMOVED error. To make it work again
we have
>>>>>>>> to
>>>>>>>> restart application (which creates new zookeeper session).
>>>>>>>>
>>>>>>>> I noticed that in 3.2.0 introduced a bug
>>>>>>>> http://issues.apache.org/jira/browse/ZOOKEEPER-449 but we
are using
>>>>>>>> zookeeper v. 3.2.2.
>>>>>>>> I just noticed that app at compile time used 3.2.0 library
but
>>>>>>>> patches
>>>>>>>> fixing bug 449 did not touch C client lib so I believe that
our
>>>>>>>> problems are not
>>>>>>>> related with that.
>>>>>>>>
>>>>>>>> In zookeeper logs at moment which initiated the problem with
client
>>>>>>>> application I have
>>>>>>>>
>>>>>>>> node1:
>>>>>>>> 2010-03-16 14:21:43,510 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@607] - Connected
to
>>>>>>>> /10.1.112.61:37197 lastZxid 42992576502
>>>>>>>> 2010-03-16 14:21:43,510 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@636] - Renewing
session
>>>>>>>> 0x324dcc1ba580085
>>>>>>>> 2010-03-16 14:21:49,443 - INFO
>>>>>>>> [QuorumPeer:/0:0:0:0:0:0:0:0:2181:NIOServerCnxn@992] - Finished
init
>>>>>>>> of 0x324dcc1ba580085 valid:true
>>>>>>>> 2010-03-16 14:21:49,443 - WARN
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@518] - Exception
causing
>>>>>>>> close of session 0x324dcc1ba580085 due to java.io.IOException:
Read
>>>>>>>> error
>>>>>>>> 2010-03-16 14:21:49,444 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@857] - closing
>>>>>>>> session:0x324dcc1ba580085 NIOServerCnxn:
>>>>>>>> java.nio.channels.SocketChannel[connected local=/10.1.112.62:2181
>>>>>>>> remote=/10.1.112.61:37197]
>>>>>>>>
>>>>>>>> node2:
>>>>>>>> 2010-03-16 14:21:40,580 - WARN
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@494] - Exception
causing
>>>>>>>> close of session 0x324dcc1ba580085 due to java.io.IOException:
Read
>>>>>>>> error
>>>>>>>> 2010-03-16 14:21:40,581 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@833] - closing
>>>>>>>> session:0x324dcc1ba580085 NIOServerCnxn:
>>>>>>>> java.nio.channels.SocketChannel[connected local=/10.1.112.63:2181
>>>>>>>> remote=/10.1.112.61:60693]
>>>>>>>> 2010-03-16 14:21:46,839 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@583] - Connected
to
>>>>>>>> /10.1.112.61:48336 lastZxid 42992576502
>>>>>>>> 2010-03-16 14:21:46,839 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@612] - Renewing
session
>>>>>>>> 0x324dcc1ba580085
>>>>>>>> 2010-03-16 14:21:49,439 - INFO
>>>>>>>> [QuorumPeer:/0:0:0:0:0:0:0:0:2181:NIOServerCnxn@964] - Finished
init
>>>>>>>> of 0x324dcc1ba580085 valid:true
>>>>>>>>
>>>>>>>> node3:
>>>>>>>> 2010-03-16 02:14:48,961 - WARN
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@494] - Exception
causing
>>>>>>>> close of session 0x324dcc1ba580085 due to java.io.IOException:
Read
>>>>>>>> error
>>>>>>>> 2010-03-16 02:14:48,962 - INFO
>>>>>>>> [NIOServerCxn.Factory:2181:NIOServerCnxn@833] - closing
>>>>>>>> session:0x324dcc1ba580085 NIOServerCnxn:
>>>>>>>> java.nio.channels.SocketChannel[connected local=/10.1.112.64:2181
>>>>>>>> remote=/10.1.112.61:57309]
>>>>>>>>
>>>>>>>> and then lots of entries like this
>>>>>>>> 2010-03-16 02:14:54,696 - WARN
>>>>>>>> [ProcessThread:-1:PrepRequestProcessor@402] - Got exception
when
>>>>>>>> processing sessionid:0x324dcc1ba580085 type:create cxid:0x4b9e9e49
>>>>>>>> zxid:0xfffffffffffffffe txntype:unknown
>>>>>>>> /locks/9871253/lock-8589943989-
>>>>>>>> org.apache.zookeeper.KeeperException$SessionMovedException:
>>>>>>>> KeeperErrorCode = Session moved
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.SessionTrackerImpl.checkSession(SessionTrackerImpl.java:231)
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.PrepRequestProcessor.pRequest(PrepRequestProcessor.java:211)
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.PrepRequestProcessor.run(PrepRequestProcessor.java:114)
>>>>>>>> 2010-03-16 14:22:06,428 - WARN
>>>>>>>> [ProcessThread:-1:PrepRequestProcessor@402] - Got exception
when
>>>>>>>> processing sessionid:0x324dcc1ba580085 type:create cxid:0x4b9f6603
>>>>>>>> zxid:0xfffffffffffffffe txntype:unknown
>>>>>>>> /locks/1665960/lock-8589961006-
>>>>>>>> org.apache.zookeeper.KeeperException$SessionMovedException:
>>>>>>>> KeeperErrorCode = Session moved
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.SessionTrackerImpl.checkSession(SessionTrackerImpl.java:231)
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.PrepRequestProcessor.pRequest(PrepRequestProcessor.java:211)
>>>>>>>>       at
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> org.apache.zookeeper.server.PrepRequestProcessor.run(PrepRequestProcessor.java:114)
>>>>>>>>
>>>>>>>>
>>>>>>>> To workaround disconnections I am going to increase session
timeout
>>>>>>>> from 5 to 15 seconds but event if it helps at all it is just
a
>>>>>>>> workaround.
>>>>>>>>
>>>>>>>> Do you have an idea where is the source of my problem.
>>>>>>>>
>>>>>>>> Regards, Łukasz Osipiuk
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>
>>>>
>>>>
>>
>>
>>
>



-- 
-- 
Łukasz Osipiuk
mailto:lukasz@osipiuk.net

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