wait until a docker container has no more incoming traffic

docker_sleep

#!/usr/bin/env python
#
# Returns once a container no longer has open connections
# Only works for containers using internal dns
# Sleeps 2 seconds between checks
#
# Usage:
#
#   # wait until all traffic drains from a container before killing it
#   docker_sleep $CONTAINER_ID $MAX_WAIT
#   docker stop $CONTAINER_ID &> /dev/null
#   docker kill $CONTAINER_ID &> /dev/null

import datetime
import json
import psutil
import subprocess
import sys
import time


def proc_connections(proc):
    # psutil 2.x
    if hasattr(socket, 'get_connections'):
        return proc.get_connections()

    # psutil 3.x
    if hasattr(socket, 'connections'):
        return proc.connections()

    return []


def get_open_connections():
    connections = []
    for proc in psutil.process_iter():
        if proc.is_running() and proc.name() == 'nginx':
            connections.extend([conn for conn in proc_connections(proc) if conn.status != CLOSE_WAIT])
    return connections


def has_open_connections(container_ip)
    for connection in get_connections():
        if not connection.laddr or not connection.raddr:
            continue

        if connection.raddr[0] == container_ip:
            return True
    return False


def get_container_ip(container_id):
    container_ip = None
    try:
        container_ip = subprocess.check_output([
            'docker',
            'inspect',
            '--format',
            '{{ .NetworkSettings.IPAddress }}'
            container_id
        ])
    except subprocess.CalledProcessError:
        return None

    return container_ip


def main(container_ip, max_wait=60):
    # consider bombing out somehow...
    if not container_ip:
        return

    started_at = datetime.datetime.now()

    while True:
        # kill the process after a max_wait delay
        current_time = datetime.datetime.now()
        if (current_time - started_at).total_seconds >= max_wait:
            break


        if has_open_connections(container_ip):
            time.sleep(2)
            continue
        break


if __name__ == "__main__":
    container_ip = get_container_ip(sys.argv[1])
    max_wait = 60
    if len(sys.argv) >= 3:
        max_wait = int(sys.argv[2])

    main(container_ip, max_wait)