PUB/SUB example extended

[douglasmccormickjr]

It seems like the PUB/SUB example could be improved (just a little bit)-- I'm getting confused that current example of pynng SUB + PUB code is all running in the same program (wouldn't this usually be running on 2 different machines, or multiple really, in practice?) I'd like to have 2 snippets of code that should be executed in separate threads/shells. The order of operation would be something like this....

(1) Run pynng_sub.py (2) Run pynng_pub.py (3) Results/msg would flow into sub based on the topics

I tried coming up with something but I'm getting some "pynng.exceptions.Timeout: Timed out" errors on the sub side...that leads me to another issue/topic related to this pattern...

Is there an elegant way to coordinate the PUB/SUB timing so the SUB is ready and will receive all the msg from PUB-- this is akin to the "Hello" msg sent to get acknowledgement that PUB and SUB are talking to each other (zmq docs mentioned this but didn't exactly show it completely, I can pull the link if it helps explain what I'm looking for better)...I'd love to know the right way to go about this so I don't hack something that's not optimal or resilient in the future.

[codypiersall]

Thanks for creating this issue, @douglasmccormickjr.

It seems like the PUB/SUB example could be improved (just a little bit)

You're talking about the example in the docs, yes? It's helpful to have feedback about the usefulness/uselessness of examples, so thanks for providing that.

My goal for the examples in the docs was to show the simplest way to use the sockets; I am putting more advanced examples in the examples directory. I should probably figure out how to integrate those with the docs as well.

Is there an elegant way to coordinate the PUB/SUB timing so the SUB is ready and will receive all the msg from PUB

Are you talking about how all the pub/sub examples always have a sleep() call to give time for the connection to establish? If so, that's something that has bothered me too. In my tests I have a function that waits for connections to be established called wait_pipe_len. Clearly this is not part of the public API—it's not even part of installable package—but it's one way to skin this cat currently. I'm sure there are more...

[MauiJerry]

Aloha Cody - i started using pynng a week or two ago for a distributed data acquisition and control system based on RPi with clients elsewhere (windoze, etc). I like the pubSub setup but like douglas, would like some more examples. In particular, I'd like more info on Topics... how do we find out what the topic is for a received msg? how do we find what topics a subscriber is subscribed to? If we use sub.recv_msg(), what can we do with the returned "Message"?

I've been spelunking a bit into the nng c code but its been a couple decades since i worked at that python/c boundary, and there is a LOT to https://github.com/nanomsg/nng

I'd like to write a dispatch(msg) that would send the message off to the proper topic handler. So do I need to do my own parsing of msg=sub.recv() ? put a divider character at end of Topic when publishing, then index on that in received msg, splitting to {topic:data} perhaps?

[MauiJerry]

I circled back to this. My app was running ok with async on the server side but needed client so I had to get the example working. The attached zip file should have the two files needed. Note, you can swap commented sections to get it running sync or async

asyncPubSub.zip `

[goodboy]

I should probably figure out how to integrate those with the docs as well.

@codypiersall use sphinx's .. literalinclude::

This is what we've done with tractor's examples and as a bonus we actually run them as tests too :smile_cat:

[goodboy]

The attached zip file should have the two files needed.

@MauiJerry why don't you just make a pull request here with the suggested changes :wink:

[MauiJerry]

I built it against older version and have more advanced demos to share soon. Im work on a TK GUI that uses pynng, trio, TK. I'll get the real app built then circle back to documentation and simple demos

• jerry isdale

sent from my phone, which may have added its own interpretation of what i typed or dictated. I apologize for any auto correct errors introduced by our robotic under lord.

On Fri, Jul 31, 2020, 12:04 PM goodboy [email protected] wrote:

The attached zip file should have the two files needed.

@MauiJerry https://github.com/MauiJerry why don't you just make a pull request here with the suggested changes 😉

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