timeout function is not safe to use

[asiunov]

Python is pretty unfriendly when interrupting threads from outside of threads. The problem is that the interruption may happen in a finalization block, which releases resources, e.g. releasing global locks. If this happen, the thread may become completely broken. So, in most cases such a function is a ticking bomb. E.g. check this code snippet:

finalization_completed = False
try:
  with timeout(2):
    try:
      print("main: started", flush=True)
      time.sleep(1)
      print("main: completed", flush=True)
    finally:
      print("finalization: started", flush=True)
      time.sleep(2)
      print("starting a very important finalization, e.g. a lock release", flush=True)
      finalization_completed = True
finally:
  print(f"finalization_completed={finalization_completed}", flush=True)

output:

main: started
main: completed
finalization: started
finalization_completed=False
Traceback (most recent call last):
  File "<stdin>", line 9, in <module>
  File "<stdin>", line 4, in _handle_timeout
TimeoutException: Timeout after 2 seconds