Add ability to reload env_file for a specific container

[joaquincasares]

Hello,

I'm not sure if this task is something that compose can handle alone, or if I also need to create a ticket against the docker project, but I figured to start here.

My use case is:

• I have ngnix, cassandra, and a web container running, via docker-compose up.
• I've updated an env_file used by the web container.
• Now, I'd wish to have my web container use the updated env_file.

If I try:

• docker-compose [stop|kill] web
• docker-compose start web

I still get my original envars that were in place at the time of docker-compose up.

How can I reload my web container to consume the updated env_file without having to do a full shutdown via docker-compose down?

Thanks for any help and guidance!

[shin-]

You would need to do docker-compose up --force-recreate web, I think. Let me know if that works!

[joaquincasares]

I gave that a shot, but it seems like a bit of a destructive path for just reloading an env_file:

$ docker-compose up --force-recreate web
Recreating project_cassandra_1
Recreating project_zookeeper_1
Recreating project_kafka_1
...

I understand that's caused by the docker-compose links definition. Thanks for the help though! Do you by chance have any other suggestions?

[Dineshs91]

docker exec -it <container_name> bash -c "source env_file"
docker restart <container_name> or docker-compose up -d <service_name>

@joaquincasares Can you try these and see if it helps ?

[MetricMike]

(as of 1.12.5) I think the .env_file directive in your docker-compose.yml is doing a couple things:

0. After a container is built, but before CMD/ENTRYPOINT is called,
1. Copy <env_file> into the container.
2. Call source <env_file>

Based on docker-compose --verbose and https://github.com/docker/compose/blob/master/compose/config/config.py it looks like docker-compose can check the env file (and volume/network settings) for changes to the configuration.

So when you run, docker-compose up, one of two things might happen assuming your Dockerfile hasn't changed and an up-to-date image has been built:

• No config changes? Don't do anything unless another option like --force-recreate is passed.
• Yes changes? Reapply any config changes needed (copy and source env_file, open ports, mnt volumes). Then call the equivalent of docker-compose restart <service> and restart the container, because docker-compose can't tell what you're running inside and what services might need a restart to pick up those config changes, refresh file handles, etc.

restart skips an important step (because docker-compose has chosen to make container configuration part of the build step, which probably isn't a terrible idea), but you shouldn't need to tear everything down to do what you want.

Hope that helps! I've been wrestling with a similar problem most of today :)

[shin-]

When a container is recreated the containers that depend on it are recreated as well, which is the behavior you want in most cases.
You could make a case for adding an option that simply reconnect the existing dependents to the new container instead, but it's honestly not very high on the list of priorities.