Re: [pysnmp-dev] Regarding use of Dispatcher with Multiprocessing
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Re: [pysnmp-dev] Regarding use of Dispatcher with Multiprocessing
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From: Ani A <ani...@gm...> - 2015-03-29 05:30:02
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Thanks ilya,
I could try this just today, due to other priorities.
So, I had to do:
encoder.encode(reqMsg)
and send it on another UDP port, and it worked. At the moment, I am not
worried about performance, as I am prototyping this as a part of a bigger
solution.
Thanks again, I will get back if in case I am stuck with anything else.
--
Regards,
A. Aniruddha
On Sat, Mar 7, 2015 at 9:11 PM, Ilya Etingof <il...@gl...> wrote:
> Hi Ani,
>
> There’s no easy way to access *parts* of serialised message. May be you
> could just decode the whole message (like you did), peek into varbinds to
> select appropriate queue and then send the whole *original* SNMP
> TRAP/INFORM message to a new destination (e.g. wholeMsg)?
>
> An alternative is to re-encode reqPDU to get serialised data just for it:
>
> from pyasn1.codec.ber import encoder
>
> rawData = encoder.encode(reqPDU)
>
> But that is less efficient.
>
> Let me know if this is not what you want.
>
> -ilya
>
>
> > On 02 Mar 2015, at 15:13, Ani A <ani...@gm...> wrote:
> >
> > Thanks Ilya,
> >
> > I looked at `snmpfwd`, I think , at the moment, I don't need the full
> > functionality, but rather just a small subset, for
> > the trap processing.
> >
> > And, one more thing I feel is, in the notification forwarder, I just
> > need to peek into the varbinds, and then if I
> > can get just the PDU (as _data_ rather than Object), I can
> > re-encapsulate it in a different UDP packet, and send
> > But I don't this there is any API to get the PDU as _raw-data_ - is
> > that correct ?
> >
> > Please see the attached code, that I have so far (I have added
> > comments on what I am trying to accomplish).
> >
> > --
> > Regards,
> > A. Aniruddha
> >
> >
> > On Sun, Mar 1, 2015 at 1:44 AM, Ilya Etingof <il...@gl...> wrote:
> >> Hi Ani,
> >>
> >> There’s similar app snmpfwd [1], however it does yet not support SNMP
> >> notifications at the moment.
> >>
> >> The most straightforward way to do a proxy with pysnmp is to run both
> sides
> >> — Notification Receiver & Notification Originator together within a
> single
> >> main loop. Since pysnmp natively supports asynchronous communication,
> while
> >> one request is waiting for I/O, the other could be served concurrently.
> But
> >> two strictly simultaneous requests would queue up at shared SNMP engine
> >> waiting for its services. Here’s an example script [2] that implements
> SNMP
> >> Commands forwarding in the above design. It could be modified to support
> >> Notifications. With pysnmp API all the low-level processing and ACKs
> could
> >> be done automatically so you could deal with PDUs and targets.
> >>
> >> If you wish to use threads, you'd have to run many independent SNMP
> engines
> >> (and main loops) local to each thread. Take a look at this example [3]
> to
> >> get an idea. In case of notifications I imagine you would have the
> receiving
> >> parts sitting each in its own main loop waiting for incoming queries and
> >> pushing received requests to a queue. The sending parts would run their
> >> main loops briefly, just to push out request and optionally wait for
> >> response (informs). So most of the time the sending parts would spend
> >> waiting for queue to pull request from.
> >>
> >> From my perspective, the threading approach may give better load
> >> distribution (but unlikely better throughput considering GIL which does
> not
> >> let you run threads truly simultaneously), however it may require more
> work
> >> from your side and larger memory footprint due to SNMP engine
> duplication.
> >>
> >> The third option could be to run multiple instances of your purely
> >> asynchronous proxy (receivers) to improve concurrency.
> >>
> >> -ilya
> >>
> >> [1] http://sf.net/projects/snmpfwd/
> >> [2]
> >>
> http://pysnmp.sourceforge.net/examples/current/v3arch/proxy/cmd/v3-to-v2c-conversion.html
> >> [3]
> >>
> http://pysnmp.sourceforge.net/examples/current/v3arch/oneliner/manager/cmdgen/get-threaded-multiple-transports-and-protocols.html
> >>
> >>
> >> On 27 Feb 2015, at 08:01, Ani A <ani...@gm...> wrote:
> >>
> >> Hi Ilya,
> >>
> >> I am trying to create something like a _proxy_, the goal is to be able
> to
> >> intercept traps from the local
> >> SNMP Agent, and then peeking into the varbinds, decide which one of the
> >> remote trap-receivers to send to.
> >>
> >> Traps are the first goal, then, for Informs, I need to be able to get
> the
> >> ack, and send it back to the main agent as well.
> >>
> >> Since I am using Multiprocessing module [1], do I still have to worry
> about
> >> MT safe?
> >>
> >> (the networking part of this, is that the receivers are all on different
> >> networks
> >> [ different Linux namespaces ], so I have to get the SNMP payload and
> then
> >> build a separate UDP packet and
> >> send, unless there is an easier way/API that I can use to just change
> the IP
> >> and send)
> >>
> >> Hope I explained the problem [that I am trying to solve], clearly. Any
> >> help/tips/guidance very much welcome.
> >>
> >>
> >> [1] https://docs.python.org/2/library/multiprocessing.html
> >>
> >> --
> >> Ani
> >>
> >>
> >> On Fri, Feb 27, 2015 at 1:09 AM, Ilya Etingof <il...@gl...> wrote:
> >>>
> >>> Hi Ani,
> >>>
> >>> At what point you are going to employ threading? Just for SNMP
> receiving
> >>> part (what is not easy since a single instance of SNMP engine is not
> >>> MT-safe) or for some sort of custom processing logic beyond SNMP
> engine?
> >>>
> >>> -ilya
> >>>
> >>>> On 24 Feb 2015, at 09:44, Ani A <ani...@gm...> wrote:
> >>>>
> >>>> Hello,
> >>>>
> >>>> I was running through the examples in pysnmp (for Trap receiver with
> V3
> >>>> case)
> >>>> and I have a few doubts (maybe trivial! but somehow I am not getting
> it)
> >>>>
> >>>> I want to use pysnmp, with Python's Multiprocessing module, so in
> >>>> each Process's callback function, do I run the following ?
> >>>>
> >>>> try:
> >>>> snmpEngine.transportDispatcher.runDispatcher()
> >>>> except:
> >>>> snmpEngine.transportDispatcher.closeDispatcher()
> >>>> raise
> >>>>
> >>>> i.e, what should my main-loop wait on? , since I have another Queue as
> >>>> well
> >>>> which I need to check.
> >>>>
> >>>> Thanks.
> >>>> —
> >>>> Ani
> >>>
> >>
> >>
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> > <snmpp.py>
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