send_message.py

import random
import time
import json
import threading
import click


def send_message(msg, async=True):
    """Logs the message to an output stream.

    If async is true, use a background thread

    Based on
    http://sebastiandahlgren.se/2014/06/27/running-a-method-as-a-background-thread-in-python/
    """

    def send(msg=msg):
        try:
            # Simulates a system where the IO could take up to 5 seconds
            time.sleep(random.random() * 5)
            print(f"Sending {msg}")  # IO
        except Exception:
            pass  # swallow any and all exceptions

    if async:
        thread = threading.Thread(target=send)
        thread.daemon = True
        thread.start()
    else:
        send()


@click.command()
@click.option('--async/--sync', is_flag=True, default=True)
def main(async):
    click.echo("Async..." if async else "Sync...")
    for i in range(10):
        send_message(json.dumps({'a': i}), async=async)

    print("I'm done logging, start the heavy processing")
    time.sleep(5)
    print("I'm done processing")


if __name__ == "__main__":
    main()

⭆ time python send_message.py
Async...
I'm done logging, start the heavy processing
Sending {"a": 0}
Sending {"a": 6}
Sending {"a": 9}
Sending {"a": 3}
Sending {"a": 5}
Sending {"a": 8}
Sending {"a": 7}
Sending {"a": 2}
Sending {"a": 1}
Sending {"a": 4}
I'm done processing

real	0m5.078s
user	0m0.058s
sys	0m0.019s


⭆ time python send_message.py --sync
Sync...
Sending {"a": 0}
Sending {"a": 1}
Sending {"a": 2}
Sending {"a": 3}
Sending {"a": 4}
Sending {"a": 5}
Sending {"a": 6}
Sending {"a": 7}
Sending {"a": 8}
Sending {"a": 9}
I'm done logging, start the heavy processing
I'm done processing

real	0m21.524s
user	0m0.058s
sys	0m0.019s

If the main process exits before the threads, any remaining threads are "orphaned" and may not complete. To avoid this, set thread.daemon = False to allow all threads to run until completion.