wtask.py

import gc
import pprint
import types
import weakref

import asyncio
from asyncio import tasks

from tornado import gen
from tornado.ioloop import IOLoop


@gen.coroutine
def infinite_coro(holder):
    print("-- infinite coro started --")
    try:
        while True:
            yield gen.sleep(0.05)
    finally:
        print("-- infinite coro finalized! --")


async def infinite_task(holder):
    print("-- infinite task started --")
    try:
        while True:
            #print("    ... infinite task")
            await gen.sleep(0.05)
    finally:
        print("-- infinite task finalized! --")


def print_refs(obj):
    assert obj is not None
    for r in gc.get_referrers(obj):
        if isinstance(r, types.FrameType):
            if r.f_code.co_name != 'print_refs':
                print(f"  - Frame: {r.f_code}")
        else:
            print(f"  - {r!r}")


def main():
    ref_cycle = []
    wcoro = wtask = None

    async def do_something():
        nonlocal wcoro, wtask

        loop.add_callback(infinite_coro, ref_cycle)
        loop.add_callback(infinite_task, ref_cycle)

        await gen.sleep(0.01)

        runner,= (r for r in gen._futures_to_runners.values()
                  if 'infinite_coro' in repr(r.gen))
        task, = (t for t in tasks.Task.all_tasks()
                 if 'infinite_task' in repr(t))
        wcoro = weakref.ref(runner.gen)
        wtask = weakref.ref(task)

        await gen.sleep(0.1)

    loop = IOLoop.current()
    print("-- starting loop --")
    loop.run_sync(do_something)
    loop.close()
    do_something = loop = ref_cycle = None
    IOLoop.clear_current()
    asyncio.get_event_loop().close()  # needed to collect the infinite task
    gc.collect()
    print("-- loop closed --")

    print()
    if wcoro() is None:
        print("== coro collected! ==")
    else:
        print("== coro refs ==")
        print_refs(wcoro())

    print()
    if wtask() is None:
        print("== task collected! ==")
    else:
        print("== task refs ==")
        print_refs(wtask())


main()