Question asked, question answered! RPiZ has only one core, thus, the number of
tasks in queue = 2. Bumping up NNG_NUM_TASKQ_THREADS to 8 solved it.
/R
From: nanomsg-bounce@xxxxxxxxxxxxx <nanomsg-bounce@xxxxxxxxxxxxx> On Behalf Of
Robert Bielik
Sent: Saturday, 28 March 2020 13:59
To: nanomsg@xxxxxxxxxxxxx
Subject: [nanomsg] Re: Concurrency problem
Oh, forgot to mention that the problem occurs when running this on a Raspberry
Pi Zero (Raspbian Stretch with RT kernel patch).
It works fine on Windows 10.
Regards
/Robert
From: nanomsg-bounce@xxxxxxxxxxxxx<mailto:nanomsg-bounce@xxxxxxxxxxxxx>
<nanomsg-bounce@xxxxxxxxxxxxx<mailto:nanomsg-bounce@xxxxxxxxxxxxx>> On Behalf
Of Robert Bielik
Sent: Saturday, 28 March 2020 13:56
To: nanomsg@xxxxxxxxxxxxx<mailto:nanomsg@xxxxxxxxxxxxx>
Subject: [nanomsg] Concurrency problem
Hi all,
I have a problem that has me tearing hair off my head. Context: I have a system
of servers which use nng (ipc) for communication (based on the request/response
demo on nng github) . The calls are synchronous and fast. I also have a REST
API built on nng which I use to control the main server
(https://github.com/robiwano/siesta<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Frobiwano%2Fsiesta&data=02%7C01%7Crobert.bielik%40dirac.com%7C1c4375e8fb6943a2a91e08d7d317cb5b%7C266f25c575d44d978f448d816a1f6a35%7C1%7C0%7C637209971456083367&sdata=zOGijmRfEF%2FTF2KzsClX%2BzBxHsPFdckl7RC7Zv9%2BqLc%3D&reserved=0>).
One of the REST API calls is an “inverted callback” which hangs for ten
seconds if nothing happens, but returns as soon as something is updated (but
only for the webclients not doing the change, identified with a 64 bit ID).
This in order to let multiple REST clients to be notified.
Now to the problem: As long as there is only one webclient using the REST API,
everything works fine. But as soon as two are connected (i.e. with two
outstanding “inverted callbacks”) everything grinds to a halt. It seems that
the IPC communication stops working properly.
Now, since nng is used in the both the IPC parts and REST server, these parts
share the underlying nng task management I would presume.
Can anyone spot anything obvious I’m doing wrong here?
Regards
/Robert
Ps. This is why I’m eager to use websockets instead of the “inverted callback”
REST calls.
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