Defining an additional service with Docker Compose

Prerequisite knowledge

Much of ddev's customization ability and extensibility comes from leveraging features and functionality provided by Docker and Docker Compose. Some working knowledge of these tools is required in order to customize or extend the environment ddev provides.

Background

Under the hood, ddev uses docker-compose to define and run the multiple containers that make up the local environment for a project. docker-compose supports defining multiple compose files to facilitate sharing Compose configurations between files and projects, and ddev is designed to leverage this ability.

To add custom configuration or additional services to your project, create docker-compose files in the .ddev directory for your project. ddev will process any files using the docker-compose.[servicename].yaml naming convention and include them in executing docker-compose functionality. Optionally you can also create a docker-compose.override.yaml to override any configurations from the main docker-compose.yaml or any additional compose files added to your project.

Restrictions on the docker-compose.yaml file

The main docker-compose.yaml file is exclusively reserved for ddev's use, and will be overwritten on ddev upgrades and when a project is started, so it should not be edited, or edits will be lost. If you need to override configuration provided by docker-compose.yaml, use an additional file to do so.

Confirming docker-compose configurations

To better understand how ddev is parsing your custom docker-compose files, you can run ddev debug compose-config to print the final docker-compose configuration as generated by ddev when starting your project.

Conventions for defining additional services

When defining additional services for your project, we recommended you follow these conventions to ensure ddev handles your service the same way ddev handles default services.

  • To name containers follow this naming convention ddev-[projectname]-[servicename]

  • Provide containers with the following labels

  • com.ddev.site-name: ${DDEV_SITENAME}

  • com.ddev.approot: $DDEV_APPROOT

  • Exposing ports for service: you can expose the port for a service to be accessible as projectname.ddev.site:portNum while your project is running. This is achieved by the following configurations for the container(s) being added:

  • Define only the internal port in the ports section for docker-compose. The hostPort:containerPort convention normally used to expose ports in docker should not be used here, since we are leveraging the ddev router to expose the ports.

  • To expose a web interface to be accessible over HTTP, define the following environment variables in the environment section for docker-compose:

    • VIRTUAL_HOST=$DDEV_HOSTNAME

    • HTTP_EXPOSE=portNum The hostPort:containerPort convention may be used here to expose a container's port to a different external port. To expose multiple ports for a single container, define the ports as comma-separated values.

Interacting with additional services

Certain ddev commands, namely ddev exec, ddev ssh, and ddev logs interact with containers on an individual basis. By default, these commands interact with the web container for a project. All of these commands, however, provide a --service or -s flag allowing you to specify the service name of the container you want to interact with. For example, if you added a service to provide Apache Solr, and the service was named solr, you would be able to run ddev logs --service solr to retrieve the logs of the Solr container.