The Shirlington Public Library during cherry blossom season.

Defining Your Own Pattern Library

Announcing Updates to the Tilt Extensions API

Tilt provides a few basic primitives for defining the local shell scripts, docker builds, and Kubernetes pods in your dev environment.

But most teams have an opinionated way to build services! For example, you might have

  • checks to make sure your laptop has the right tools,

  • conventions for building images,

  • custom scripts for deploying objects,

  • custom buttons for debugging services!

As of v0.25, Tilt has a new API for managing your own repo of Tiltfile snippets, so that you can easily set some standards across multiple repos or multiple projects.

Let’s take a quick tour of the extension system and how it works:

Using an Extension

Let’s look at the hello_world extension.

The source code for this extension is here and has exactly two (2) lines of code:

def hi():
  print("Hello world!")

It exports one function, hi, that simply prints “Hello world!”.

Let’s load this extension into our project:

load('ext://hello_world', 'hi')
hi()

When you run tilt ci in this project, you’ll see output like:

Initial Build • (Tiltfile)
Loading Tiltfile at: /home/nick/src/scratch/Tiltfile
Hello world!
Successfully loaded Tiltfile (1.990905ms)
ERROR: No resources found. Check out https://docs.tilt.dev/tutorial.html to get started!

Tilt printed the message! Tilt also printed an error because it doesn’t make any sense to have a dev environment that only prints “Hello world!”. 🙃

Managing Your Own Extension Repo

The new v1alpha1.extension_repo API1 lets you change the behavior of load().

Let’s start with the hello_world example above:

load('ext://hello_world', 'hi')

This is a shorthand with nice defaults. You could write it like this:

v1alpha1.extension_repo(name='default', url='https://github.com/tilt-dev/tilt-extensions')
v1alpha1.extension(name='hello_world', repo_name='default', repo_path='hello_world')
load('ext://hello_world', 'hi')

These two snippets are equivalent. The second snippet explicitly spells out that there’s an extension repo called default at https://github.com/tilt-dev/tilt-extensions. The extension hello_world gets loaded from the path hello_world in the default repo.

This API lets you fork the shared tilt-extensions repo, and instruct load() to pull from there:

v1alpha1.extension_repo(name='default', url='https://github.com/my-org/tilt-extensions')
load('ext://hello_world', 'hi')

Alternatively, you can add new extension repos alongside the default one.

v1alpha1.extension_repo(name='my-repo', url='https://github.com/my-org/tilt-extensions')
v1alpha1.extension(name='hello_world', repo_name='my-repo', repo_path='hello_world')
load('ext://hello_world', 'hi')

Notice that in the above, we define hello_world to pull its source from my-repo rather than default.

If your extension repo is private, you’ll need to configure git to authenticate against the private repo in the background. A common pattern (borrowed from the Go FAQ) is to setup your Git repo for SSH and add these lines to your ~/.gitconfig:

[url "ssh://git@github.com/"]
	insteadOf = https://github.com/

Sharing Extensions with the Community

If you have an extension that you think would be generally useful, we love to see people contribute them back to the main repo!

For more detail on the new extension system, check out:

  1. The v1alpha1 part of the API indicates that this is an object in the Tilt API server, matching the Kubernetes API conventions. You can use tilt get extension or tilt get extensionrepo as a CLI to see information about the extensions currently in your dev env. 

Related

Keep up with Developments in Multi-Service Development
 
 
 
Keep up with Developments in Multi-Service Development

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