Hai semuanya, di materi kali ini kita akan membahas tentang Service Dependencies dalam Compose file.

Service Dependency adalah the most-common dalam pengembangan aplikasi, component paling basic atau minimal biasanya kita memerlukan database atau external service. Sebagai contoh misalnya klo kita menjalankan aplikasi tapi tanpa database maka akan terjadi failure.

Pada Compose file, ada depends_on. Express dependency between services. Service dependencies cause the following behaviors:

  1. docker-compose up starts services in dependency order. In the following example, db and migrate-tool are started before web.
  2. docker-compose up SERVICE automatically includes SERVICE’s dependencies. In the example below, docker-compose up web also creates and starts db and migrate-tool.
  3. docker-compose stop stops services in dependency order. In the following example, web is stopped before db.
version: '3.9'
services:
web:
image: nginx
ports:
- "80:80"
volumes:
- ./html:/usr/share/nginx/html
depends_on:
- postgres
- migrate-tools
postgres:
image: postgres:12.6
ports:
- 5432:5432
environment:
- POSTGRES_PASSWORD
- POSTGRES_USER
- POSTGRES_DB
volumes:
- pg_data:/var/lib/postgresql/data
migrate-tools:
image: flyway/flyway:latest-alpine
environment:
- FLYWAY_EDITION
command: ["-user=${POSTGRES_USER}", "-password=${POSTGRES_PASSWORD}", "-url=jdbc:postgresql://postgres:5432/${POSTGRES_DB}", "info"]
depends_on:
- postgres
volumes:
pg_data: { }
view raw 09l-depend-on.docker-compose.yaml hosted with ❤ by GitHub

Dan berikut adalah file .env:

# database postgresql
POSTGRES_PASSWORD=secretPassword
POSTGRES_USER=bisnis_app
POSTGRES_DB=bisnis_app
# flyway migration tools
FLYWAY_EDITION=community
view raw 09l-depend-on.env hosted with ❤ by GitHub

Jika di jalankan maka hasilnya seperti berikut:

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml config
services:
  migrate-tools:
    command:
    - -user=bisnis_app
    - -password=secretPassword
    - -url=jdbc:postgresql://postgres:5432/bisnis_app
    - info
    depends_on:
      postgres:
        condition: service_started
    environment:
      FLYWAY_EDITION: community
    image: flyway/flyway:latest-alpine
  postgres:
    environment:
      POSTGRES_DB: bisnis_app
      POSTGRES_PASSWORD: secretPassword
      POSTGRES_USER: bisnis_app
    image: postgres:12.6
    ports:
    - published: 5432
      target: 5432
    volumes:
    - pg_data:/var/lib/postgresql/data:rw
  web:
    depends_on:
      migrate-tools:
        condition: service_started
      postgres:
        condition: service_started
    image: nginx
    ports:
    - published: 80
      target: 80
    volumes:
    - C:\Users\dimasm93\Workspaces\youtube\docker\09-docker-compose\dependency\html:/usr/share/nginx/html:rw
version: '3.9'
volumes:
  pg_data: {}

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency up -d
Creating network "dependency_default" with the default driver
Creating volume "dependency_pg_data" with default driver
Creating dependency_postgres_1 ... done
Creating dependency_migrate-tools_1 ... done
Creating dependency_web_1           ... done

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency ps
           Name                         Command               State                     Ports
---------------------------------------------------------------------------------------------------------------
dependency_migrate-tools_1   flyway -user=bisnis_app -p ...   Exit 0
dependency_postgres_1        docker-entrypoint.sh postgres    Up       0.0.0.0:5432->5432/tcp,:::5432->5432/tcp
dependency_web_1             /docker-entrypoint.sh ngin ...   Up       0.0.0.0:80->80/tcp,:::80->80/tcp

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency logs migrate-tools
Attaching to dependency_migrate-tools_1
migrate-tools_1  | Flyway Community Edition 7.14.0 by Redgate
migrate-tools_1  | Database: jdbc:postgresql://postgres:5432/bisnis_app (PostgreSQL 12.6)
migrate-tools_1  | Schema version: << Empty Schema >>
migrate-tools_1  |
migrate-tools_1  | +----------+---------+-------------+------+--------------+-------+
migrate-tools_1  | | Category | Version | Description | Type | Installed On | State |
migrate-tools_1  | +----------+---------+-------------+------+--------------+-------+
migrate-tools_1  | | No migrations found                                            |
migrate-tools_1  | +----------+---------+-------------+------+--------------+-------+
migrate-tools_1  |

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency down
Stopping dependency_web_1      ... done
Stopping dependency_postgres_1 ... done
Removing dependency_web_1           ... done
Removing dependency_migrate-tools_1 ... done
Removing dependency_postgres_1      ... done
Removing network dependency_default

# testing start from service name: migrate-tools
➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency up -d migrate-tools
Creating network "dependency_default" with the default driver
Creating dependency_postgres_1 ... done
Creating dependency_migrate-tools_1 ... done

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency down
Stopping dependency_postgres_1 ... done
Removing dependency_migrate-tools_1 ... done
Removing dependency_postgres_1      ... done
Removing network dependency_default

# testing start from service name: web
➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency up -d web
Creating network "dependency_default" with the default driver
Creating dependency_postgres_1 ... done
Creating dependency_migrate-tools_1 ... done
Creating dependency_web_1           ... done

➜ docker  docker-compose -f .\09-docker-compose\dependency\docker-compose.yaml -p dependency down --volumes
Stopping dependency_web_1      ... done
Stopping dependency_postgres_1 ... done
Removing dependency_web_1           ... done
Removing dependency_migrate-tools_1 ... done
Removing dependency_postgres_1      ... done
Removing network dependency_default
Removing volume dependency_pg_data

There are several things to be aware of when using depends_on:

  1. depends_on does not wait for db and migrate-tools to be “ready” before starting web - only until they have been started. If you need to wait for a service to be ready, see Controlling startup order for more on this problem and strategies for solving it.
  2. The depends_on option is ignored when deploying a stack in swarm mode with a version 3 Compose file.