Structure

Every application you deploy on Platform.sh is built as a virtual cluster, containing a set of containers. The master branch of your Git repository is always deployed as the production cluster. Any other branch can be deployed as a development cluster. By default, you can have up to three live development clusters at once, but you can buy more on a per-project basis.

There are three types of containers within your cluster:

  • one Router
  • one or more Application containers
  • zero or more Service containers

When deployed, they conceptually look like this:

All of those containers are managed by three special files in your Git repository:

  • .platform/routes.yaml
  • .platform/services.yaml
  • .platform.app.yaml

In most cases, that means your repository will look like this:

yourproject/
  .git/
  .platform/
    services.yaml
    routes.yaml
  .platform.app.yaml
  <your application files>

Router

There is always exactly one Router per cluster.

The Router of a cluster is a single nginx process. It is configured by the routes.yaml file. It maps incoming requests to the appropriate Application container and provides basic caching of responses, if so configured. It has no persistent storage.

Service

Service containers are configured by the services.yaml file.

There may be zero or more Service containers in a cluster, depending on the services.yaml file. The code for a Service is provided by Platform.sh in a pre-built container image, along with a default configuration. Depending on the service it may also include user-provided configuration in the services.yaml file. Examples of services include MySQL/MariaDB, Elasticsearch, Redis, and RabbitMQ.

Application

There always must be one Application container in a cluster, but there may be more.

Each Application container corresponds to a .platform.app.yaml file in the repository. If there are 3 .platform.app.yaml files, there will be three Application containers. Application containers hold the code you provide via your Git repository. Application containers are always built off of one of the Platform.sh-provided language-specific images, such as “PHP 5.6”, “PHP 7.2”, or “Python 3.7”. It is also possible to have multiple Application containers running different languages or versions.

For typical applications, there is only one .platform.app.yaml file, which is generally placed at the repository root.