Python script to catch the Docker SIGTERM signal

README.md

Python - Catch SIGTERM signal

Overview

This Docker image will catch the SIGTERM signal and then take STOP_TIMEOUT seconds to cleanup.

Getting Started

$ # Build the Docker image.
$ docker build -t slow-stop .

$ # Run the container, when the SIGTERM is received spend 10 seconds doing "cleanup".
$ docker run -dit -e STOP_TIMEOUT=10 -p 8000:8000 slow-stop:latest

Dockerfile

FROM python:3-onbuild

EXPOSE 8000

CMD ["./server.py"]

server.py

#!/usr/bin/env python3
"""

    Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.

    Licensed under the Apache License, Version 2.0 (the "License").
    You may not use this file except in compliance with the License.
    A copy of the License is located at

        http://www.apache.org/licenses/LICENSE-2.0

    or in the "license" file accompanying this file. This file is distributed
    on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
    express or implied. See the License for the specific language governing
    permissions and limitations under the License.

"""
import time
import signal
import os

from multiprocessing import Process

from flask import Flask, jsonify

STOP_TIMEOUT = int(os.environ.get('STOP_TIMEOUT', '10'))
PORT = int(os.environ.get('PORT', '8000'))

APP = Flask(__name__)


@APP.route('/')
def home():
    return jsonify(**{'status': 'ok'}), 200


def run():
    APP.run(host='0.0.0.0', port=PORT)


def signal_handler(sig, _frame):
    """Handling the SIGTERM event"""
    print(f'Received signal {sig} - stopping gracefully')
    count = STOP_TIMEOUT
    while count > 0:
        print(f'cleaning up: {count}')
        time.sleep(1)
        count -= 1
    print('Finished cleanup...')


def main():
    # Create a process and pipe to pass messages to the process.
    process = Process(target=run)
    process.start()
    signal.signal(signal.SIGTERM, signal_handler)
    signal.pause()
    process.join()


if __name__ == "__main__":
    main()