R: Re: [SNMP4J] IllegalStateException in Snmp.send()
Frank Fock
fock at agentpp.com
Fri Dec 15 01:56:39 CET 2006
Hi Alberto,
According to your and the others' information I have
revisited the current synchronous Snmp.send(..) code
and found a possible cause of the exception.
Please try out the following modification of the
synchronous send method. The difference is the
additional "synchronized" block with the comment:
public ResponseEvent send(PDU pdu, Target target,
TransportMapping transport) throws
IOException {
...
if (retryRequest != null) {
retryRequest.setFinished();
// We need to synchronize here to make sure that the retryRequest
// is already scheduled when we cancel it. Otherwise it might be
// canceled before being scheduled which results in an
// IllegalStateException being thrown in the retry handler.
synchronized (sync) {
retryRequest.cancel();
}
}
...
}
Is my assumption correct that you are using synchronous
requests?
Best regards,
Frank
Alberto wrote:
> Thanks a lot Frank for being so quick.
> Before posting my message, I read all contributions in the mailing list about
> the topic, checked my code and I am reasonably sure no Snmp.close() is called.
> I have a single static instance of Snmp used for all requests sent (from
> different threads) to the agents. Snmp session is allocated the first time and
> never closed (it dies together with the application). After allocating Snmp
> session the first time, Snmp.listen() is called.
> There is another Snmp session allocated for trap receival. Again here Snmp.
> listen() is called and it is closed at application shutdown.
> So ... still dark from my side.
> Question: is the Snmp.close() traced in snmp4j logs? Because I cannot see
> anything about that.
> Moreover: is there any other possibility leading to the problem I described
> and related to a misuse of snmp4j lib from my side?
>
> PS If you need complete snmp4j logs with debug level, tell me.
>
> Ciao,
> Alberto
>
>
>> ----Messaggio originale----
>> Dal: fock at agentpp.com
>> Data: 14/12/2006 0.55
>> A: "Alberto"<alberto_mascheroni at fastwebnet.it>
>> Cc: <snmp4j at agentpp.org>
>> Ogg: Re: [SNMP4J] IllegalStateException in Snmp.send()
>>
>> Hello Alberto,
>>
>> You wrote that you had to restart your application
>> in order to use your Snmp instance again after
>> having caught the error below. This indicates,
>> that the timer referred to in the exception,
>> had been canceled. That means that your code
>> somewhere called Snmp.close() while requests
>> where pending.
>>
>> That is how it is supposed to work: If you close
>> the Snmp instance, then it is shutdown and
>> cannot be used again. You will need to instantiate
>> a new Snmp instance.
>>
>> So please do not call Snmp.close() between two
>> queries!
>>
>> Hope this helps.
>>
>> Best regards,
>> Frank
>>
>> Alberto wrote:
>>> Hello,
>>> I refer to the correction provided in v1.7.1 and described by Frank in
> email
>>> below.
>>> Since I got the same problem in my project, I downloaded the SNMP4J
> version
>>> 1.7.5 and reproduced the error with log4j logs enabled.
>>> Here the result (just reported the PduHandle with the problem, but if you
> need
>>> I have the complete logs):
>>>
>>> 13/12/2006 14:30:30:131 DEBUG [pool-10-thread-22] [Log4jLogAdapter.debug]
> New
>>> pending request with handle PduHandle[1826954335]
>>> ...
>>> 13/12/2006 14:30:45:579 DEBUG [Timer-15] [Log4jLogAdapter.debug] Running
>>> pending request (3 left) with handle: PduHandle[1826954335]
>>> ...
>>> 13/12/2006 14:31:00:587 DEBUG [Timer-15] [Log4jLogAdapter.debug] Running
>>> pending request (2 left) with handle: PduHandle[1826954335]
>>> ...
>>> 13/12/2006 14:31:00:589 DEBUG [SNMPDriverDispatchPool.2] [Log4jLogAdapter.
>>> debug] Looking up pending request with handle PduHandle[1826954335]
>>> ...
>>> 13/12/2006 14:31:00:591 ERROR [Timer-15] [Log4jLogAdapter.error] Failed to
>>> process pending request PduHandle[1826954335] because Task already
> scheduled or
>>> cancelled
>>> java.lang.IllegalStateException: Task already scheduled or cancelled
>>> at java.util.Timer.sched(Timer.java:358)
>>> at java.util.Timer.schedule(Timer.java:170)
>>> at org.snmp4j.Snmp$PendingRequest.run(Snmp.java:1426)
>>> at java.util.TimerThread.mainLoop(Timer.java:512)
>>> at java.util.TimerThread.run(Timer.java:462)
>>> ...
>>> 13/12/2006 14:31:00:590 DEBUG [pool-10-thread-22] [Log4jLogAdapter.debug]
>>> Removed pending request with handle: PduHandle[1826954335]
>>> ...
>>>
>>> It seems there is a relation between the time the Timer-15 is checking the
>>> handle for the second time (14:31:00:587) and the time the answer comes (14:
> 31:
>>> 00:589). They are really very closed one to the other.
>>> Maybe a synchronization problem among threads?
>>>
>>> Of course, after Timer-15 thread dies, no Snmp primitive to the agent is
>>> possible anymore and my application has to be restarted.
>>>
>>> Can you help, please?
>>> Regards,
>>> Alberto
>>>
>>>
>>> Frank wrote:
>>>
>>>> Hi Fabian,
>>>>
>>>> We can catch only a RuntimeException and rethrow it. I have
>>>> changed the code as follows for v1.7.1:
>>>>
>>>> /**
>>>> * run
>>>> */
>>>> public synchronized void run() {
>>>> try {
>>>> if ((!finished) && (retryCount > 0)) {
>>>> ...
>>>> }
>>>> }
>>>> catch (RuntimeException ex) {
>>>> logger.error("Failed to process pending request "+key+
>>>> " because"+ex.getMessage(), ex);
>>>> throw ex;
>>>> }
>>>>
>>>> Best regards,
>>>> Frank
>>>>
>>>
>>> --------------------
>>> Alberto Mascheroni
>>> Mob. +39-333-6314222
>>> _______________________________________________
>>> SNMP4J mailing list
>>> SNMP4J at agentpp.org
>>> http://lists.agentpp.org/mailman/listinfo/snmp4j
>> --
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>>
>>
>
>
>
> --------------------
> Alberto Mascheroni
> Mob. +39-333-6314222
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