docker_django_management.py 文件源码

def wait_for_db(max_attempts=15, seconds_between_attempts=1):
    # type: (int, int) -> None
    '''
    Some manage.py commands interact with the database, and we want
    them to be directly callable from `docker-compose run`. However,
    because docker may start the database container at the same time
    as it runs `manage.py`, we potentially face a race condition, and
    the manage.py command may attempt to connect to a database that
    isn't yet ready for connections.

    To alleviate this, we'll just wait for the database before calling
    the manage.py command.
    '''

    from django.db import DEFAULT_DB_ALIAS, connections
    from django.db.utils import OperationalError

    connection = connections[DEFAULT_DB_ALIAS]
    attempts = 0

    while True:
        try:
            connection.ensure_connection()
            break
        except OperationalError as e:
            if attempts >= max_attempts:
                raise e
            attempts += 1
            time.sleep(seconds_between_attempts)
            info("Attempting to connect to database.")

    info("Connection to database established.")