Improve support for external event loops. #235
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@joernheissler Just wanted to say thanks for doing this. This is going to be very useful. 👍 |
examples/loop_asyncio.py
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| class AsyncioHelper: | ||
| def __init__(self, loop, client): | ||
| self.loop = loop | ||
| self.client = client = client |
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examples/loop_select.py
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| client.subscribe(topic) | ||
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| def on_message(self, client, userdata, msg): | ||
| if self.state not in {1,3,5}: |
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I would prefer to see the positive case first, so that the else clause doesn't mean "not not in {...}".
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I removed the "else". I prefer to have a program flow where the "good" case is always on the top indention level and all the bad cases just exit the function as soon as possible. "if this is bad, abort. If that is bad, abort. What's remaining must be good."
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Any chance that would be merged and included in next release? |
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Add four more callbacks and documentation to make it possible to use external event loops other than select(). This could e.g. be asyncio, twisted or gevent. * on_socket_open - called when a new socket was opened. --> watch read * on_socket_close - called when the socket is about to be closed. --> unwatch read * on_socket_register_write - called when mqtt wants to write. --> watch write * on_socket_unregister_write - called when mqtt is finished writing. --> unwatch write Add examples how to write external event loops: * loop_select.py - select() based event loop, works without the other changes. * loop_asyncio.py - asyncio based event loop, utilizes the new callbacks. This should also fix the issues eclipse#72 and eclipse#147. Signed-off-by: Jörn Heissler <eclipse.org@wulf.eu.org>
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I made some minor improvements to the documentation, and loop_misc in the asyncio example is now started from a callback. |
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Thanks for this PR, it add good support for asyncio to paho-mqtt. While reviewing it, I'm wondering if our multiple loops support is not too complicated. My view is that
My question is then: should we keep all those loops ? What if the default loop is an
Did you see any issue with going that way ? Any use case that require a custom base loop that a default asyncio won't match ? |
Asyncio was only added in py 3.4. Unless you want to anger your users (#204) you shouldn't depend on asyncio. Personally I don't care about py < 3.5, but I suspect others do. The socket() and want_write() methods could be removed in my opinion. Instead, a select style loop can use the new callbacks and keep two lists of file descriptors that need watching (reading+writing). If a callback is called, those lists are modified. What you could do too is move the existing loops from the Client class to an extra module and perhaps keep a stub method with the old signature so existing code won't break. Those loops would use the new callbacks. |
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I though that asyncio existed on PyPI for older Python... but that not the case. It could be possible to fallback on select based loop that being said. |
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The develop branch only supports Python 2.7 or 3.4+, and you can use https://github.com/haypo/trollius for Python 2.7 for asyncio. It certainly feels like supporting the standard Python mechanism for asynchronous I/O would be a significant improvement. |
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Actually, looks like trollius is abandoned and probably wouldn't be very helpful anyway since it would lack the keyword support. |
#72, #147, https://dev.eclipse.org/mhonarc/lists/paho-dev/msg03997.html and https://github.com/mossblaser/aiomqtt demonstrate that the current support for external event loops should be improved.
https://dev.eclipse.org/mhonarc/lists/paho-dev/msg03999.html suggests to add new callbacks to track the state of the library. That's what my change implements.