Service containers

Azure Pipelines

If your pipeline requires the support of one or more services, in many cases you'll want to create, connect to, and clean up each service on a per-job basis. For instance, a pipeline may run integration tests that require access to a database and a memory cache. The database and memory cache need to be freshly created for each job in the pipeline.

A container provides a simple and portable way to run a service that your pipeline depends on. A service container enables you to automatically create, network, and manage the lifecycle of your containerized service. Each service container is accessible by only the job that requires it. Service containers work with any kind of job, but they're most commonly used with container jobs.

Requirements

Service containers must define a CMD or ENTRYPOINT. The pipeline will docker run the provided container without additional arguments.

Azure Pipelines can run Linux or Windows Containers. Use either hosted Ubuntu for Linux containers, or the Hosted Windows Container pool for Windows containers. (The Hosted macOS pool does not support running containers.)

Single container job

A simple example of using container jobs:

resources:
  containers:
  - container: my_container
    image: buildpack-deps:focal
  - container: nginx
    image: nginx


pool:
  vmImage: 'ubuntu-20.04'

container: my_container
services:
  nginx: nginx

steps:
- script: |
    curl nginx
  displayName: Show that nginx is running

This pipeline fetches the nginx and buildpack-deps containers from Docker Hub and then starts the containers. The containers are networked together so that they can reach each other by their services name.

From inside this job container, the nginx host names resolves to the correct services using Docker networking. All containers on the network automatically expose all ports to each other.

Single job

You can also use service containers without a job container. A simple example:

resources:
  containers:
  - container: nginx
    image: nginx
    ports:
    - 8080:80
    env:
      NGINX_PORT: 80
  - container: redis
    image: redis
    ports:
    - 6379

pool:
  vmImage: 'ubuntu-18.04'

services:
  nginx: nginx
  redis: redis

steps:
- script: |
    curl localhost:8080
    echo $AGENT_SERVICES_REDIS_PORTS_6379

This pipeline starts the latest nginx containers. Since the job is not running in a container, there's no automatic name resolution. This example shows how you can instead reach services by using localhost. In the above example we provide the port explicitly (for example, 8080:80).

An alternative approach is to let a random port get assigned dynamically at runtime. You can then access these dynamic ports by using variables. In a Bash script, you can access a variable by using the process environment. These variables take the form: agent.services.<serviceName>.ports.<port>. In the above example, redis is assigned a random available port on the host. The agent.services.redis.ports.6379 variable contains the port number.

Multiple jobs

Service containers are also useful for running the same steps against multiple versions of the same service. In the following example, the same steps run against multiple versions of PostgreSQL.

resources:
  containers:
  - container: my_container
    image: ubuntu:18.04
  - container: pg12
    image: postgres:12
  - container: pg11
    image: postgres:11

pool:
  vmImage: 'ubuntu-18.04'

strategy:
  matrix:
    postgres12:
      postgresService: pg12
    postgres11:
      postgresService: pg11

container: my_container

services:
  postgres: $[ variables['postgresService'] ]
steps:
- script: printenv

Ports

When specifying a container resource or an inline container, you can specify an array of ports to expose on the container.

resources:
  containers:
  - container: my_service
    image: my_service:latest
    ports:
    - 8080:80
    - 5432

services:
  redis:
    image: redis
    ports:
    - 6379/tcp

Specifying ports is not required if your job is running in a container because containers on the same Docker network automatically expose all ports to each other by default.

If your job is running on the host, then ports are required to access the service. A port takes the form <hostPort>:<containerPort> or just <containerPort>, with an optional /<protocol> at the end, for example 6379/tcp to expose tcp over port 6379, bound to a random port on the host machine.

For ports bound to a random port on the host machine, the pipeline creates a variable of the form agent.services.<serviceName>.ports.<port> so that it can be accessed by the job. For example, agent.services.redis.ports.6379 resolves to the randomly assigned port on the host machine.

Volumes

Volumes are useful for sharing data between services, or for persisting data between multiple runs of a job.

You can specify volume mounts as an array of volumes. Volumes can either be named Docker volumes, anonymous Docker volumes, or bind mounts on the host.

services:
  my_service:
    image: myservice:latest
    volumes:
    - mydockervolume:/data/dir
    - /data/dir
    - /src/dir:/dst/dir

Volumes take the form <source>:<destinationPath>, where <source> can be a named volume or an absolute path on the host machine, and <destinationPath> is an absolute path in the container.

Note

If you use our hosted pools, then your volumes will not be persisted between jobs because the host machine is cleaned up after the job is completed.

Other options

Service containers share the same container resources as container jobs. This means that you can use the same additional options.

Healthcheck

Optionally, if any service container specifies a HEALTHCHECK, the agent waits until the container is healthy before running the job.