Environment variables in Compose

Hai semuanya di materi kali ini kita akan membahas Environment variable khususnya dalam Compose file, diantaranya

1. Set environtment variable in container
2. The .env file
3. Operation System environment variables
4. Using the --env-file option
5. Pass environment variables to containers
6. The env_file configuration option
7. Set environment variables with docker-compose run

Ok langsung ja, kita ke pembahasan yang pertama yaitu

Set environtment variable in container

You can set environment variables in a service’s containers with the environment key, just like with docker run -e VARIABLE=VALUE ...:

The .env file

You can set default values for any environment variables referenced in the Compose file, or used to configure Compose, in an environment file named .env. The .env file path is as follows:

1. Starting with +v1.28, .env file is placed at the base of the project directory
2. Project directory can be explicitly defined with the --file option or COMPOSE_FILE environment variable. Otherwise, it is the current working directory where the docker compose command is executed (+1.28).
3. For previous versions, it might have trouble resolving .env file with --file or COMPOSE_FILE. To work around it, it is recommended to use --project-directory, which overrides the path for the .env file. This inconsistency is addressed in +v1.28 by limiting the filepath to the project directory.

Contohnya kita buat file .env seperti berikut:

Dan berikut adalah file docker-compose.yaml seperti berikut:

When you run docker-compose up, the web service defined above uses the image nginx:1.12.1. You can verify this with the config command, which prints your resolved application config to the terminal:

➜ env-file  docker-compose config
services:
  web:
    image: nginx:1.21.1
    ports:
    - published: 80
      target: 80
version: '3.8'

Operation system environment variables

Selain menggunakan .env file, compose file juga listen dari OS Environtment variable, sebagai contoh kita masih menggunakan docker-compose.yaml sebelumnya yaitu:

Sekarang coba set env variable di OS dengan perintah seperti berikut:

For Bash script:

export NGINX_VERSION=latest

For Powershell script:

$Env:NGINX_VERSION="latest"

Sekarang coba check dengan perintah seperti berikut docker-compose config, maka hasilnya seperti berikut:

## perintah berikut akan meng-override file `.env` file karena levelnya lebih tinggi
➜ env-file  $Env:NGINX_VERSION="latest"
➜ env-file  docker-compose config
services:
  web:
    image: nginx:latest
    ports:
    - published: 80
      target: 80
version: '3.8'

# To remove Env NGINX_VERSION from Session
➜ env-file  Remove-Item Env:NGINX_VERSION

here’s the priority used by Compose to choose which value to use:

1. Compose file
2. Shell environment variables
3. Environment file
4. Dockerfile
5. Variable is not defined

Using the --env-file option

By passing the file as an argument, you can store it anywhere and name it appropriately, for example, .env.ci, .env.dev, .env.prod. Passing the file path is done using the --env-file option:

docker-compose -f .env.dev config

Jika di jalankan maka hasilnya seperti berikut:

## create copy file of `.env` to `.env.dev`
➜ env-file  cp .env .env.dev
# the edit value in `.env.dev` file
➜ env-file  sed -i 's|1.21.1|mainline|g' .env.dev

➜ env-file  cat .env.dev
NGINX_VERSION=mainline

➜ env-file  docker-compose --env-file .env.dev config
services:
  web:
    image: nginx:mainline
    ports:
    - published: 80
      target: 80
version: '3.8'

Pass environment variables to containers

You can pass environment variables from your shell straight through to a service’s containers with the ‘environment’ key by not giving them a value, just like with docker run -e VARIABLE ...:

Buat file baru dengan nama .env seperti berikut:

Dan berikut adalah file docker-compose.yaml seperti berikut:

Jika kita coba validate maka hasilnya seperti berikut:

➜ pass-env  cat .env
POSTGRES_PASSWORD=test_db
DB_USERNAME=test_db
POSTGRES_DB=test_db

➜ pass-env  cat docker-compose.yaml
version: '3.8'
services:
  db:
    image: postgres:12.6
    environment:
      - POSTGRES_PASSWORD
      - POSTGRES_USER=${DB_USERNAME}
      - POSTGRES_DB
    ports:
      - 5432:5432

➜ pass-env  docker-compose --env-file .env config
services:
  db:
    environment:
      POSTGRES_DB: test_db
      POSTGRES_PASSWORD: test_db
      POSTGRES_USER: test_db
    image: postgres:12.6
    ports:
    - published: 5432
      target: 5432
version: '3.8'

The value of the POSTGRES_DB variable in the container is taken from the value for the same variable in the shell in which Compose is run.

The env_file configuration option

You can pass multiple environment variables from an external file through to a service’s containers with the env_file option, just like with docker run --env-file=FILE ...:

Buat file baru dengan nama database.dev.env seperti berikut:

Dan berikut adalah file docker-compose.yaml seperti berikut:

Jika kita coba validate maka hasilnya seperti berikut:

➜ env-file-option  docker-compose config
services:
  db:
    environment:
      POSTGRES_DB: hr_db
      POSTGRES_PASSWORD: dev_db
      POSTGRES_USER: dev_db
    image: postgres:12.6
    ports:
    - published: 5432
      target: 5432
version: '3.8'

Set environment variables with docker-compose run

Similar to docker run -e, you can set environment variables on a one-off container with docker-compose run -e:

Berikut adalah docker-compose.yaml template:

Kemudian coba jalan perintah berikut

docker-compose -f .\docker-compose.yaml run \
-e POSTGRES_DB=hr_db \
-e POSTGRES_USER=prod_db \
db

Jika dijalankan maka hasilnya seperti berikut:

➜ docker-compose-run  docker-compose -f .\docker-compose.yaml run `
>> -e POSTGRES_DB=hr_db `
>> -e POSTGRES_USER=prod_db `
>> -d db

Creating docker-compose-run_db_run ... done
docker-compose-run_db_run_bef93b57be79

➜ docker-compose-run  docker-compose ps
                 Name                               Command              State    Ports
-----------------------------------------------------------------------------------------
docker-compose-run_db_run_bef93b57be79   docker-entrypoint.sh postgres   Up      5432/tcp

➜ docker-compose-run  docker container inspect docker-compose-run_db_run_bef93b57be79 -f '{{json .Config.Env}}' | python.exe -m json.tool
[
    "POSTGRES_PASSWORD=hr_db",
    "POSTGRES_DB=hr_db",
    "POSTGRES_USER=prod_db",
    "PGDATA=/var/lib/postgresql/data"
]