postgresql-sync.py

# coding: utf-8
from datetime import datetime
from time import sleep

from psycopg2 import connect, OperationalError


connected = False
while not connected:
    try:
        connection = connect(host='db', dbname='postgres', user='postgres')
    except OperationalError:
        print("Couldn't connect at %s, waiting 4 s ." % datetime.now())
        sleep(4)
    else:
        connected = True
        connection.close()

def can_connect(retries=10):
    delay = 1
    
    for _ in range(retries):
        try:
            with connect(host='db', dbname='postgres', user='postgres') as connection:
                # test the connection
            connection.close()
            return True
        except OperationalError:
            print("Couldn't connect at %s, waiting 4 s ." % datetime.now())
            sleep(delay)
            delay = min(delay * 2, 60)

    return False