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Resource Dependencies

Say you have a web service specified in a Tilt resource named frontend and a database in a Tilt resource named database, and frontend fails to even start up if database isn’t running. This can lead to distracting errors on startup (especially, e.g., if you have 5 services all depending on the same backend!)

Tilt allows you to specify that frontend depends on database, so that frontend will not be deployed until database has been successfully deployed:

k8s_resource('frontend', resource_deps=['database'])

This has two effects:

  1. frontend will not be deployed until database has been ready at least once since Tilt was started.
  2. If you run tilt up frontend to select only some of your Tiltfile’s resources, that also implicitly selects all of frontend’s transitive dependencies.

A resource is “ready” when:

  • For K8s resources: the pod is running and K8s considers all of its containers ready
  • For docker-compose resources: the container is started (NB: Tilt doesn’t currently observe docker-compose health checks)
  • For local resources: the command has succeeded at least once

Some other use cases:

  • Define your resource deps such that it’s easy to bring up only the services you need for what you’re currently working on. e.g., tilt up frontend starts not just frontend, but also the database and the assets server.
  • Create a local_resource to generate language bindings from protobuf schemas, and make the services that use those language bindings depend on that local resource.

Caveat: This feature currently mostly only helps in the common case that different versions of services are broadly compatible with each other, and focuses on ensuring that some instance of a resource’s dependencies exist, without worrying too much about whether it’s a current version. For this reason, resource_deps currently only affects the first build after a tilt up. e.g., Once any version of database has been running at least once, its dependencies are unblocked to build for the rest of Tilt’s lifetime.

We think this feature is useful as-is, but are aware there are more possibilities for it. Please reach out if it’s not meeting your needs!