Bug: Starting multiple containers at once in parallel causes Conflict by starting ryuk container multiple times due to race condition

Describe the bug

Starting two testcontainers at once triggers both of them to call Reaper._create_instance close in time. Both Reaper instances attempt to create the same ryuk container (since SESSION_ID is the same).

This is relevant when using pytest-parallel, which my organization does. I can probably work around the problem by serializing testcontainer start() calls on one thread.

To Reproduce

from testcontainers.postgres import PostgresContainer
import concurrent.futures


def start_postgres_container(port: int):
    with PostgresContainer(port=port) as postgres:
        print("Postgres is running on port", postgres.get_exposed_port(port))


with concurrent.futures.ThreadPoolExecutor() as executor:
    future1 = executor.submit(start_postgres_container, port=5400)

    # Uncommenting this reliably avoids the error
    # import time
    # time.sleep(5)
    future2 = executor.submit(start_postgres_container, port=5401)
    future1.result()
    future2.result()

Runtime environment

Provide a summary of your runtime environment. Which operating system, python version, and docker version are you using? What is the version of testcontainers-python you are using? You can run the following commands to get the relevant information.

# Get the operating system information (on a unix os).
$ uname -a
Darwin xxx 24.1.0 Darwin Kernel Version 24.1.0: Thu Oct 10 21:03:11 PDT 2024; root:xnu-11215.41.3~2/RELEASE_ARM64_T6020 arm64 arm Darwin
$ python --version
Python 3.11.10
$ docker info
# Get all python packages.
$ pip freeze
certifi==2024.8.30
charset-normalizer==3.4.0
docker==7.1.0
idna==3.10
requests==2.32.3
testcontainers==4.8.2
typing_extensions==4.12.2
urllib3==2.2.3
wrapt==1.17.0

Reaper._create_instance から始め、issue にある concurrent.futures の再現を 2 つの PostgresContainer インスタンスで実行します。完了条件は、同時起動で ryuk コンテナを複数回作成しようとしても Conflict が発生しなくなり、両方のコンテナが正常に起動することです。