Well, conducting a fairly difficult research in the field of the multiple
thread Net-SNMP applications, I found out that you cannot use threads
whith the same "init_snmp(argv[0])" statement. The post I read did not
give any other information, just this: you can have multiple sessions with
the same init_snmp(), but ONLY if you are NOT using threads.. No other
explanation was given. That's why I'm so stuck. I have no idea how to
implement a multi-threaded net-snmp client with one session per thread,
with no SegFaults..
If anyone has a tutorial, a how-to or a code snippet regarding the
aforementioned problem, please please PLEASE share!
> Hi Katia S:
> I have been using multiple threads where each thread starts a client and
> maintains a single session. I am using this for Informs as opposed to the
> get/set.
> In all the usage documentation it was found that we need to perform
> init_snmp("PROGNAME"), once for all threads. Each thread creates a
> session using the single session APIs. I would also like to know if the
> init_snmp needs to be done per session as stated by you below. If
> init_snmp is done once per process and snmp_sess_open is used to create a
> valid snmp session within each thread context then multiple threads
> maintaining one session per thread works as expected.
> Thanks
> Mukund
>
>
>
> On Fri, Sep 7, 2012 at 5:15 AM, Katia Sarsempagieva <
> kat...@iit.demokritos.gr> wrote:
>
>> **
>> Greetings everyone!
>> I have already and extensively searched answers for the particular
>> problem,
>> but I failed to find any. So, if this topic has already been answered, I
>> apologize.
>>
>> Problem Context:
>> ---------------------------------
>> Let's say I have a MIB that contains a table.
>> And I have written a multi-threaded Net-SNMP Client application that
>> reads
>> and writes
>> to the mentioned MIB.
>> Each thread writes on its own Index. For example, only one thread will
>> write and read the
>> row with Index = 1 (myTable.1), so I do not have to lock any rows or
>> tables to add thread protection.
>> (The second thread will work on Index = 2 (myTable.2), and so on and so
>> forth).
>>
>> Each thread creates its own SNMP Session. It initializes a session with
>> the name "ThreadID=Index",
>> where "Index" is the Index of the row the particular thread will play
>> with.
>> (Example: init_snmp("ThreadIndex=1"); )
>> Later, it creates a Session and opens it.
>> With the open Session, it uses get and set code to play with the MIB and
>> at the end it closes the Session.
>>
>>
>> Problem Question:
>> ---------------------------------
>> Are the mentioned assumptions even correct?
>> Is it possible to have a multi-threaded Net-SNMP Client with one session
>> per thread?
>> If yes, what are the rules that have to be followed in order to avoid
>> SegFaults, that are occurring at my program
>> at random times (usually when the client changes to another thread or
>> when
>> a thread gets a "NULL" response via
>> a snmp_synch_response function)?
>>
>> Environment:
>> ---------------------------------
>> Just in case, I post the environment parameters in which I am working.
>>
>> OS: Debian, Linux
>> Net-SNMP Version: 5.7.1 (source code installation)
>> Threading Lib: pthread.h
>> Net-SNMP Client and Server, both on Localhost
>> Programming Language: C
>>
>> Any insight on the aforementioned problem and any useful advice will be
>> greatly appreciated!
>> Thank you very much in advance!
>>
>> Best regards,
>>
>> --
>> *Katia Sarsempagieva*
>>
>> * Research Assistant
>> Media Network Laboratory
>> Institute of Information and Telecommunications
>> NCSR Demokritos
>> *
>>
>>
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>>
>
--
(Under Investigation) Research Associate
Media Networks Laboratory
Institute of Networks and Telecommunications
NCSR Demokritos
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