Calling a coroutine from asyncio.Protocol.data
This is similar to Calling coroutines in asyncio.Protocol.data_received but I think it warrants a new question.
I have a simple server set up like this
loop.create_unix_server(lambda: protocol, path=serverSocket)
It works fine, if I do this
def data_received(self, data):
data = b'data reply'
self.send(data)
my client gets the reply. But I can't get it to work with any sort of asyncio call. I tried all of the following and none of them worked.
@asyncio.coroutine
def go(self):
yield from asyncio.sleep(1, result = b'data reply')
def data_received(self, data):
print('Data Received', flush=True)
task = asyncio.get_event_loop().create_task(self.go())
data = yield from asyncio.wait_for(task,10)
self.send(data)
that one hung and printed nothing (if I decorated data_received with @asyncio.coroutine I get that that is not yielded from) OK, I get that using yield in data_received isn't right.
If I try a new event loop, as below, that hangs in run_until_complete
loop = asyncio.new_event_loop()
task = loop.create_task(self.go())
loop.run_until_complete(task)
data = task.result()
self.send(data)
If I use a Future , that also hangs in run_until_complete
@asyncio.coroutine
def go(self, future):
yield from asyncio.sleep(1)
future.set_result(b'data reply')
def data_received(self, data):
print('Data Received', flush=True)
loop = asyncio.new_event_loop()
future = asyncio.Future(loop=loop)
asyncio.async(self.go(future))
loop.run_until_complete(future)
data = future.result()
self.send(data)
The following gets close, but it returns immediately and the result is of type asyncio.coroutines.CoroWrapper , implying that the wait_for line returned immediately with the unfinished task?
@asyncio.coroutine
def go(self):
return(yield from asyncio.sleep(3, result = b'data reply'))
@asyncio.coroutine
def go2(self):
task = asyncio.get_event_loop().create_task(self.go())
res = yield from asyncio.wait_for(task, 10)
return result
def data_received(self, data):
print('Data Received', flush=True)
data = self.go2()
self.send(data)
I'm a bit stuck really, and would appreciate some pointers about what to look at.
You need to add your coroutine to the event loop, and then use Future.add_done_callback to handle the result when the coroutine completes:
@asyncio.coroutine
def go(self):
return(yield from asyncio.sleep(3, result = b'data reply'))
def data_received(self, data):
print('Data Received', flush=True)
task = asyncio.async(self.go()) # or asyncio.get_event_loop().create_task()
task.add_done_callback(self.handle_go_result)
def handle_go_result(self, task):
data = task.result()
self.send(data)
Calling a coroutine directly in data_received just simply isn't allowed, since the caller isn't going to try to yield from it, and creating/running a new event loop inside of data_received will always end up blocking the main event loop until the inner event loop finishes its work.
You just want to schedule some work with your main event loop ( asyncio.async / loop.create_task() ), and schedule a callback to run when the work is done ( add_done_callback ).
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