tsuru.yaml

tsuru.yaml is a special file located in the root of the application. The name of the file may be tsuru.yaml or tsuru.yml. (app.yaml or app.yml are also supported for backward compatibility reasons, however this will be dropped soon.)

This file is used to describe certain aspects of your app. Currently it describes information about deployment hooks and deployment time health checks. How to use this features is described below.

Deployment hooks

tsuru provides some deployment hooks, like restart:before, restart:after and build. Deployment hooks allow developers to run commands before and after some commands.

Here is an example about how to declare this hooks in your tsuru.yaml file:

hooks:
  restart:
    before:
      - python manage.py generate_local_file
    after:
      - python manage.py clear_local_cache
  build:
    - python manage.py collectstatic --noinput
    - python manage.py compress

tsuru supports the following hooks:

  • restart:before: this hook lists commands that will run before the unit is restarted. Commands listed in this hook will run once per unit. For instance, imagine there’s an app with two units and the tsuru.yaml file listed above. The command python manage.py generate_local_file would run two times, once per unit.
  • restart:after: this hook is like before-each, but runs after restarting a unit.
  • build: this hook lists commands that will be run during deploy, when the image is being generated.

Healthcheck

You can declare a health check in your tsuru.yaml file. This health check will be called during the deployment process and tsuru will make sure this health check is passing before continuing with the deployment process.

If tsuru fails to run the health check successfully it will abort the deployment before switching the router to point to the new units, so your application will never be unresponsive. You can configure the maximum time to wait for the application to respond with the docker:healthcheck:max-time config.

Here is how you can configure a health check in your yaml file:

healthcheck:
  path: /healthcheck
  method: GET
  status: 200
  match: .*OKAY.*
  allowed_failures: 0
  • healthcheck:path: Which path to call in your application. This path will be called for each unit. It is the only mandatory field, if it’s not set your health check will be ignored.
  • healthcheck:method: The method used to make the http request. Defaults to GET.
  • healthcheck:status: The expected response code for the request. Defaults to 200.
  • healthcheck:match: A regular expression to be matched against the request body. If it’s not set the body won’t be read and only the status code will be checked. This regular expression uses go syntax and runs with . matching \n (s flag).
  • healthcheck:allowed_failures: The number of allowed failures before that the health check consider the application as unhealthy. Defaults to 0.