Services

Crow provides a services: section in the pipeline config file for “service” containers. These are static daemon services like databases or APIs which are then used/consumed by other containers within the pipeline. To illustrate possible use cases, the below examples uses a “database” and a “cache” service.

Hostnames

Services are accessed via DNS using their assigned hostnames. In the example below, the MySQL service is assigned the hostname database and is subsequently available at database:3306.

steps:
  - name: build
    image: golang
    commands:
      - go build
      - go test

services:
  - name: database
    image: mysql

  - name: cache
    image: redis

Ports and Protocol

Defining ports and their protocol is supported:

services:
  - name: database
    image: mysql
    ports:
      - 3306

  - name: wireguard
    image: wg
    ports:
      - 51820/udp

Configuration

Service containers allow exposing environment variables to customize their startup.

services:
  - name: database
    image: mysql
    environment:
      - MYSQL_DATABASE=test
      - MYSQL_ALLOW_EMPTY_PASSWORD=yes

  - name: cache
    image: redis

Tmpfs

Service containers like databases benefit greatly from tmpfs mounts, which store data in RAM instead of on disk. This can significantly speed up test pipelines.

services:
  - name: database
    image: postgres:18
    tmpfs:
      - /var/lib/postgresql
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres

  - name: cache
    image: mysql:9
    tmpfs:
      - /var/lib/mysql
    environment:
      MYSQL_DATABASE: test
      MYSQL_ALLOW_EMPTY_PASSWORD: 'yes'

See the tmpfs section in the workflow syntax for more details on size limits and mount options.

Detachment

Services always start at the beginning of a workflow, asynchronously to any other step.

With the detach option, the execution order can be controlled in a more granular way. This setting allows using normal steps as implicit “service” steps which honor the specified execution order. These steps will also terminate at the end of the workflow.

steps:
  - name: build
    image: golang
    commands:
      - go build
      - go test

  - name: database
    image: redis
    detach: true

  - name: test
    image: golang
    commands:
      - go test

Initialization

Service containers require time to initialize and begin accepting connections. If the service is not yet available when the first step tries to connect and using detach is not an option, adding a short sleep command can help:

steps:
  - name: test
    image: golang
    commands:
      - sleep 15
      - go get
      - go test

services:
  - name: database
    image: mysql

Full example

services:
  - name: database
    image: mysql
    environment:
      - MYSQL_DATABASE=test
      - MYSQL_ROOT_PASSWORD=example
steps:
  - name: get-version
    image: ubuntu
    commands:
      - ( apt update && apt dist-upgrade -y && apt install -y mysql-client 2>&1 )> /dev/null
      - sleep 20s # need to wait for mysql-server init
      - echo 'SHOW VARIABLES LIKE "version"' | mysql -u root -h database test -p example