connection_pool_example.py

from uuid import uuid4
from time import sleep
import threading
from concurrent.futures import ThreadPoolExecutor, as_completed

THREAD_LOCAL = threading.local()


def connect():
    """
    Create the connection for the thread
    """
    THREAD_LOCAL.connection = uuid4()  # a dummy value which is unique


def run(name):
    """
    Run the blocking operation against the thread's connection
    """
    connection = THREAD_LOCAL.connection
    print("Hello from {} in {}".format(name, connection))
    sleep(2)
    print("Bye from {} in {}".format(name, connection))


with ThreadPoolExecutor(initializer=connect, max_workers=2) as pool:
    futures = [
        pool.submit(run, str(i)) for i in range(5)
    ]
    as_completed(futures)