totaltimeout 2.0.0

Spread one timeout over many operations

Spread one timeout over many operations.

Correctly and efficiently spreads one timeout over many steps by recalculating the time remaining after some amount of waiting has already happened, to pass an adjusted timeout to the next step.

Versioning

This library’s version numbers follow the SemVer 2.0.0 specification.

Installation

pip install totaltimeout

Usage

Import the Timeout class.

from totaltimeout import Timeout

Waiting in a “timed loop” for an API with retries (useful for unreliable APIs that may either hang or need retries):

for time_left in Timeout(SOME_NUMBER_OF_SECONDS):
     reply = requests.get(some_flaky_api_url, timeout=time_left)
     if reply.status == 200:
         break

Same as above, but with a wait between retries:

timeout = Timeout(SOME_NUMBER_OF_SECONDS)
for time_left in timeout:
     reply = requests.get(some_flaky_api_url, timeout=time_left)
     if reply.status == 200:
         break
     if timeout.time_left() <= RETRY_DELAY:
         break
     time.sleep(RETRY_DELAY)

Waiting for multiple tasks to finish:

timeout = Timeout(10.0)
my_thread_foo.join(timeout.time_left())
my_thread_bar.join(timeout.time_left())
my_thread_qux.join(timeout.time_left())
# Wait only as long as the slowest
# thread to finish, as if they all
# got a 10 second wait in parallel.

Waiting for multiple tasks within each iteration of a “timed loop”:

timeout = Timeout(SOME_NUMBER_OF_SECONDS)
for time_left in timeout:
     foo.some_work(timeout=time_left)
     # The first timeout can be *either* be the for loop value or
     # the ``time_left()`` method. The rest *have to be* the latter.
     foo.some_more_work(timeout=timeout.time_left())
     some_other_work(timeout=timeout.time_left())

Using a monotonic clock instead of the wall clock:

import time

timeout = Timeout(10.0, now=time.monotonic)

You can also set the starting point in time of the timeout, which is useful when you need a repeating timeout on an interval, and you don’t want that interval to drift or you you want that interval to stay faithful to the wall clock time:

INTERVAL = 60
beginning_of_interval = (time.now() // INTERVAL) * INTERVAL
while True:
    timeout = Timeout(INTERVAL, start=beginning_of_interval)
    metric_values = []
    for time_left in timeout:
        metric_values.append(get_metric())
    average_and_report(metric_values)
    beginning_of_interval += INTERVAL

Explanation

If you’re confused about what’s going on, run this example program:

from time import sleep

from totaltimeout import Timeout

def demo(timeout_in_seconds):
    timeout = Timeout(timeout_in_seconds)
    for time_left in timeout:
        print(time_left)
        sleep(1)
        print(timeout.time_left())
        sleep(1)

if __name__ == '__main__':
    demo(10)

You should get output kinda like this:

9.99990844912827
8.996184696443379
7.992705063894391
6.990415567532182
5.983945298939943
4.981594786979258
3.979213748127222
2.9768632212653756
1.9745127055794
0.9699955033138394