Async freezes in nimqml-application

[R3D9477]

Hi. I strange behavior of async/await operaions, when I called into nimqml-signal.
ChatServer freezes at server.nim:38
chat_server_app.zip

Here is client for test:
async_client_server.zip
(also in this client can be tested server.nim without nimqml and it works fine)

Any ideas?

[dom96]

I haven't looked at your code, but I'm guessing you haven't properly integrated into the nimqml event loop? You likely need to call some sort of QML poll function together with the asyncdispatch poll function.

[R3D9477]

@dom96 well, what I trying to do:

1. to start server:

...
  proc btnStartClicked*(self: MainWindowHandler, serverPort: int) {.slot.} =
    self.chatServer.start(serverPort)
    serverStartedChanged(self, self.chatServer.started)
...

2. to call procedure 'start' after button clicked:

...
proc start*(server: Server, serverPort: int) =
  server.socket = newAsyncSocket()
  server.started = true
  server.socket.bindAddr(serverPort.Port)
  server.socket.listen()
  server.loopTask = loop(server)
...

3. then to launch async task 'loop', who will wait for clients:

...
proc loop(server: Server) {.async.} =
  echo 000000000
  while server.started:
    echo 111111111
    let (netAddr, clientSocket) = await server.socket.acceptAddr()
    echo 222222222
    ...
...

nothing more.

and as result output I have:

0
111111111

client tells me about successfully connection, but in that time server doesn't go to next line echo 222222222

[filcuc]

@r3d9u11 @dom96

Qt is not made (usually) for being called by other threads and you must be careful on doing that.
Usually Qt should "own" the main thread for multiple reasons (initialization of static QtObjects in .so libraries that must be destroyed on app exit thus on the same thread).
Honestly i don't have a lot of experience in integrating Qt with other event loops. The best approach is to separate your async server from the main thread and communicate with an "Actor" like pattern. In the worst case split the server and the UI in two different processes and communicate with a Pipe or ZMQ or nanomsg

[R3D9477]

@filcuc thanks for hint, I'll try to play with threading. but I'll leave this issue to be open, yet

[R3D9477]

@dom96 async procedures isn't GC safe? Is it possible to call async procedure from another procedure who called in a new thread via spawn?

[dom96]

You can write {.async, gcsafe.}, no?

[R3D9477]

@dom96 yes, thanks! (sorry I'm a novice in Nim, yet)

[filcuc]

@r3d9u11 @dom96
probably i've just to export the QApplication::processEvents() in the DOtherSide library

[R3D9477]

@filcuc can it help to solve this situation?

[filcuc]

I will give it a look asap

[filcuc]

with filcuc/dotherside@b6fcb52 in place i can proceed and fix this issue

[R3D9477]

@filcuc
great news!
can I close this issue?

[filcuc]

No yet. I'll close this one when i add the bindings in NimQml. After that i would like to create a test project that integrates nim async with Qt event loop. Let's see if it's feasible. Il giorno ven 4 ott 2019 alle ore 09:21 r3d9u11 <[email protected]> ha scritto:

…

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