Trinity handling of KeyboardInterrupt

[pipermerriam]

What is wrong?

Currently, trinity is not correctly handling KeyboardInterrupt for asyncio loop based processes.

How can it be fixed

Fill this in if you know how to fix it.

We need to make use of the asyncio.loop.add_signal_handler API to do proper keyboard interrupt signal handling.

[namratachaudhary]

asyncio is very low-level

For KeyboardInterrupt, there are varied behaviours. Check this issue : python/asyncio#341

It depends on how you trigger KeyboardInterrupt. When there is a callback that doesn't return - you need to use the signal to break through that, eg a loop like

while True: 
    pass

Adding asyncio.loop.add_signal_handler might not work because it wouldn't stop such a loop.

Otoh, if there's an event loop or a queue running, and you do not want the signal to interrupt that routine, you can use asyncio.loop.add_signal_handler .

Another way to do it (naively), would be :

loop = asyncio.get_event_loop()

tasks = asyncio.gather(
        asyncio.async(some_task(second=5)),
        asyncio.async(some_task(seconds=10))
    )

try:
    loop.run_until_complete(tasks)
except KeyboardInterrupt as e:
    print("Caught keyboard interrupt..")
    tasks.cancel()
    loop.run_forever()
    tasks.exception()
finally:
    loop.close()