Compose: How to use `COMPOSE_PROJECT_NAME`?

[Mahmoudz]

I'm using the latest version of everything and the v2 of docker compose.

• I tried to set it in the docker-compose.yml file with no luck as there's no clear reference on where to place it exactly?
• I tried to add it in an .env file but didn't read it!
• I also tried to add it in the command and it keeps giving an error.

docker-compose up -d -p anything   nginx php mysql

docker-compose up -d --project-name anything   nginx php mysql

I'm more interested in adding it to the docker-compose file.
The main reason is I want to override the default project name which is the directory name.

[ryanweal]

I have to do this to work around the issue you have been running into:

COMPOSE_PROJECT_NAME=project docker-compose up

... and within my docker-compose.yml file I use the variable with the following syntax:

${COMPOSE_PROJECT_NAME}

So essentially I have the same problem that you do, but fortunately this workaround has been serving me well.

Note that if you set the variable on a separate line of the script it will not be read... same as setting it in .env as you have noted.

I would really like for the -p switch to work, it is much easier to remember and to type!

[ryanweal]

It may be worth noting that I'm on Ubuntu 14.04 in this case... I'm curious if the -p switch works on other platforms.

[nschoe]

Where are we on this? Is it solved for you @ryanweal, @mahmoudz?

From docker-compose --help:

Usage:
docker-compose [-f ...] [options] [COMMAND] [ARGS...]

So you have to use the -p before the up which is a command.

So it's expected that docker-compose up -p projectName doesn't work as it should be docker-compose -p projectName up.

Can you try and see if this solves your problems?

Hope this helped :-)

[ryanweal]

I could not get the -p switch to work at all. The environment variable only worked if it was passed on the same line as the up command. I could have used an entirely different variable but I'm hoping that this flag will start working at some point.

[ryanweal]

Here is what I get when I try the suggested format:
rcw@mojito:~/katli$ docker-compose -p sf up
WARNING: The COMPOSE_PROJECT_NAME variable is not set. Defaulting to a blank string.
Starting sf_db_1
Recreating sf_php56_1
Recreating sf_php7_1
Attaching to sf_db_1, sf_php56_1, sf_php7_1

What is curious is that it appears to have named the containers correctly in spite of the warning. I've seen it start up boxes with a null value before though, not sure if it was this same syntax or not. So I guess it might work... but with an unexpected warning.

[nschoe]

@ryanweal Yes, it's perfectly normal:

• when you previously saw boxes started with a null value before, it was because your -p was misplaced.
• Now that -p is placed correctly, docker-compose created the containers with the right name.

Now for COMPOSE_PROJECT_NAME, I think you have mistaken its usage, here is how it works:

when you use docker-compose to create containers, it needs a "project name" to preprend to the container's name, as you saw. If you don't specify -p option, docker-compose looks for an environment varaible named COMPOSE_PROJECT_NAME, and if it's empty, it defaults to the current working directory.

So you have three scenarii :

1. if you don't care about project name because you will only launch ONE docker-compose stack, then don't use anything ^^
2. if you simply need to set a project name to preprend the name of your containers, use the -p option
3. if you need to set the project name to preprend thename of your container AND you need to access the project name inside the docker-compose file, via ${COMPOSE_PROJECT_NAME} then you should use export the ENV variable COMPOSE_PROJECT_NAME.

From what I understand of your last post, it _seems_ that you are setting the project name with -p (and it does preprend the name of the containers, as you saw) but then you expect the COMPOSE_PROJECT_NAME to be set, which is not. docker-compose does not (to my knowledge) set the COMPOSE_PROJECT_NAME variable when you set the name with -p, this ENV variable only used by docker-compose to look for a project name.

Hope this helped!

[ryanweal]

Ah, so basically if I need to use a custom variable I'll have to provide the variable twice... once for myself and once for docker-compose. That seems inefficient. I'll stick to setting the COMPOSE_PROJECT_NAME variable in my case then.

[nschoe]

No I don't understand why you would say that if you need to use a custom variable you have to define it twice. It's just that the -p option is used to give docker-compose a project-name so it can preprend the name of each containers (so that, in turn, you can launch multiple compose stacks).

It's just that _you_ expected that it defined an ENV variable too, named COMPOSE_PROJECT_NAME, which is doesn't. So there is nothing wrong here.

_If_ you need to define, go ahead and do it :-)

[yashgt]

As reported on the forum at https://forums.docker.com/t/unable-to-use-compose-project-name-in-docker-compose/30157, the COMPOSE_PROJECT_NAME nor the -p seem to work in docker-compose 1.10.0. It did work for 1.8.0.

[yashgt]

COMPOSE_PROJECT_NAME is a documented env var. Refer to https://docs.docker.com/compose/reference/envvars/

[melkamar]

Just stumbled upon this now. I think what is confusing about this scenario is that setting the COMPOSE_PROJECT_NAME environment variable will:

1. allow that variable to be used in the docker-compose.yml file
2. change the project name that docker compose will use.

Because -p is used to change the 2., it's reasonable to expect that it will also affect 1.. (Or, at least, it was reasonable for me and the original poster of this issue).

The key difference here is that the environment variable is _only_ used for reading by docker compose. It will not be automatically populated. (Contrast that to e.g. CI environment where the environment variables are provided for you to _consume_.)

The current way this works is fine, but I think the documentation could use an explicit warning about this.

[borja]

I totally agree with @melkamar. If I want to define any other item (e.g. network names) using the project name as a prefix, the ENV variable is mandatory. Docs are a bit confusing at this point.

networks: ["${COMPOSE_PROJECT_NAME}-network"]

• https://docs.docker.com/compose/reference/envvars/#compose_file#compose_project_name
• This should refer only for container names.. (+1: Maybe an interesting feature here...)