Compose: Improve variable interpolation, required flag and default value.

[aramalipoor]

As first proposed in #1377 I think it would be very useful to have a way to set a variable as required, and also set some default value.

web:
   image: org/app:${VERSION?} # Required

Or

web:
   image: org/app:${VERSION:latest} # Default Value

[majidgolshadi]

:+1:

[dustinblackman]

:+1:

[armab]

:+1: for defaults.

[valeriangalliat]

:+1:

[mseashor]

:+1:

[shane-axiom]

+1

[bennycornelissen]

:+1:

[plouc]

I'm working on a project where people have heterogeneous env, I'm working on OSX and some are using Ubuntu, when using docker-machine with virtualbox provider, I have to put the full path to make Volume works:

myservice:
  volumes:
    - ${HOST_VOLUME_PATH}/src:/src

The problem is now people who don't use virtualbox have to define the value, it should be great if we could have a default value:

myservice:
  volumes:
    - ${HOST_VOLUME_PATH:.}/src:/src

In other words :+1:

[obazoud]

:+1:

[jlrigau]

:+1:

[scasagrande-d2l]

+1

[leogamas]

:+1:

[roll]

:+1:

[asilluron]

:+1:

[digitalLumberjack]

:+1:

[hadim]

This feature is a must have. Any devs from the docker-compsose team working on it ? If not I could propose a PR.

[dnephin]

While having defaults would be really nice, we haven't decided on any implementations yet.

I (personally) think it's more likely we go with something like #2636 for default values. It supports more use-cases, and doesn't require us to invent new syntax for defaults.

[marcellodesales]

I'd like to see the same implementation as https://docs.docker.com/engine/reference/builder/#environment-replacement Right now, I'd like the ability to switch from 2 different implementations for the log driver.

Given the following Base implementation:

intuitive-syslog:
  log_driver: "syslog"
  labels:
    - net.c.d.datacenter: ${DATA_CENTER}
    - net.c.d.env: ${NPMO_ENV}
    - net.c.d.hostname: ${HOSTNAME}
    - net.c.d.role: ${NPMO_ROLE}

intuitive-json:
  log_driver: "json"
  labels:
    - net.c.d.datacenter: ${DATA_CENTER}
    - net.c.d.env: ${NPMO_ENV}
    - net.c.d.hostname: ${HOSTNAME}
    - net.c.d.role: ${NPMO_ROLE}

I'd like to run the syslog driver by default and select the regular logs while debugging.

mycouch:
  extends:
    file: base.yml
    service: intuitive-${LOG_DRIVER:-syslog}
  build: roles/couchdb
  restart: always
  ports:
    - "5984"
  log_opt:
    syslog-tag: "mycouch"

myredis:
  extends:
    file: base
    service: intuitive-${LOG_DRIVER:-syslog}
  image: redis
  restart: always
  expose:
    - "6379"
  log_opt:
    syslog-tag: "myredis"

I'm getting the following error:

docker-compose -f services/new1.yml ps
ERROR: Invalid interpolation format for "extends" option in service "myredis": "intuitive-${LOG_DRIVER:-syslog}"

[gittycat]

:+1: for both required and default values.
I actually believe variables should be required by default but it might be too late for that now.

[matleh]

+1 - without this, the usefulness of variable expansion (which is a great feature) is severely limited

[marcellodesales]

Just hit this problem again :(

$ docker-compose  up    
ERROR: Invalid interpolation format for "env_file" option in service "rabbitmq": "env/${DATA_CENTER:-aws}/${ENV:-dev}.env"

I agree with @matleh, without this in docker-compose, this is definitely useless...

[marcellodesales]

Please please support the same features ALREADY SUPPORTED in Dockerfile https://docs.docker.com/engine/reference/builder/#environment-replacement

[marcellodesales]

@aramalipoor Can you update the description of this issue to include the link to the currently supported variable interpolation as of Dockerfile?

thanks!

[marcellodesales]

The section https://docs.docker.com/compose/compose-file/#variable-substitution describes that it is not supported... If this gets implemented, this documentation should be updated.

[mazerty]

:+1:

[eduardoleal]

👍

[Cosmicist]

👍 to have this implemented the same way as in the Dockerfile implementation

[bufface]

:+1:

[rubycut]

👍

[xeor]

Anyone got any news about this, it's been a whole 27 days since the last :+1: ?
Much much needed!

[jpbochi]

is there a PR already open with this change? Perhaps we need a volunteer to implement it.

[phutchins]

Definitely need this...

[hadim]

There is no reason to not implement this...

[bongole]

+1

[daleobrien]

👍 +1

[kouki-o]

+1

[shin-]

Closing via #3108

[shane-axiom]

:tada: