[SNMP4J] Safely executing TreeUtils.getSubtree in concurrent threads

[Nigel Thomas]

Frank

The client is mine. There is no separate agent - I am directly addressing
snmpd in ubuntu (on localhost at present, though eventually it will be
monitoring a distributed application running on a handful of local
servers). Traffic level should be reasonable - polling hrStorageTable and
hrSWRunTable every 30 seconds.

I will investigate timeout changes tomorrow. Thanks and any more
suggestions always welcome

Regards Nigel




On 19 June 2014 19:30, Frank Fock <fock at agentpp.com> wrote:

> Hi Nigel,
>
> Your setup is absolutely fine and the recommended one for that task.
> Have you checked that the agent isn't the problem?
> Agents (except AGENT++ and SNMP4J-Agent based) are often single
> threaded and many do not implement thread safe lexicographic ordering
> correctly.
>
> Also check the timeout values, because the agent will need more than
> twice the time if polled concurrently from two threads (if not
> multi-threaded).
>
> Best regards,
> Frank
>
> Am 19.06.2014 19:32, schrieb Nigel Thomas:
>
>> Hi
>>
>> I have a system with multiple threads getting different SNMP subtrees from
>> the same target server concurrently using TreeUtils.getSubtree. One thread
>> alone seems to work exactly as expected, but when a second thread starts
>> up
>> the two get confused; the first table receives no data.
>>
>> Clearly I am having some sort of thread safety problem - but with which
>> object/method? I am using
>> - a singleton instance of Snmp
>> - a single instance of CommunityTarget (for each monitored server -
>> currently just localhost)
>> - therefore a single instance of TransportMapping - a
>> DefaultUdpTransportMapping; I have tried
>> setAsyncMsgProcessingSupported(true)
>> - a separate instance of TreeUtils per thread
>> - SNMPv2
>> - snmp4j-2.3.0
>>
>> Any thoughts would be very welcome
>>
>> TIA
>>
>> Nigel
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>>
>
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