Achilles SDK

The Achilles SDK offers efficient operator/controller creation by allowing engineers to focus on defining their automation business logic, modeled as transitions between resources states (i.e. an FSM). This significantly lessens the knowledge of controller and Kubernetes plumbing typically required to build controllers. It also forces standardization to ensure consistency amongst controllers at Reddit, providing common functionality such as metrics, logging, reusable API structs, etc..

See the achilles-token-controller repo for a complete, runnable example of an Achilles SDK backed controller.

High Level Walkthrough

As an example, assume you wanted to create a declarative API that allows developers to request object storage for their application. The API you wish to expose may look something like:

apiVersion: infra.snooguts.net/v1alpha1
kind: ObjectStorage
metadata:
  name: persistent-storage
  namespace: web-apps
spec:
  encrypted: true
  region: us-east
  versioning: true

To define this API, you'll use a common-convention with Go structs to automatically generate the CustomResourceDefinition (API). Then you'll define the states and transition logic, such as:

Along with doing the underlying plumbing to support this controller, achilles-sdk is providing you logging, metrics, rate-limiting, and more.

Lastly, in modeling your controller logic this way, you end up with a clean directed graph that models a finite-state-machine (FSM). This can significantly reduce the cognitive overhead of reasoning about what a controller is doing or the state an object is in. More on FSM in the documentation.

Documentation

• Reconciler (FSM) Framework
  • Overview of how achilles-sdk works by offering a finite-state machine orchestrated with a Kubernetes reconciler.

How to Contribute

1. Fork the repo.
2. Make changes and test.
3. Submit a Pull Request with an appropriate description.
4. Tests will automatically run for you.
5. Merge PR once it is approved.

Releasing

Regular releases will be done by maintainers.

After incorporating your changes into the achilles-sdk repository, you can publish a new release to make the updated functionality available for repos that consume achilles-sdk.

Publish a new release:

1. Navigate to the GHE releases page for achilles-sdk and click the “Draft a new release” button in the top right
2. Choose the appropriate next semantic version (major.minor.patch):
   • If there are breaking code changes (e.g., new function signatures for public functions), increment the minor version if the release is pre-1.0, otherwise increment the major version
   • If there are no breaking changes, increment the patch version if pre-1.0, otherwise increment the minor version if adding functionality or the patch version if fixing bugs
   • To create a tag with the new version, click the “Choose a tag” button. Enter the new version number and click “Create new tag: $your-tagname-here on publish.”
3. Click the “Generate release notes” button and verify that the changes align with expectations. If everything looks good, publish the release

Make updated functionality available for repos consuming the achilles-sdk:

1. Create a branch in the consuming repository
2. Run the following command to upgrade the achilles-sdk version (replace v0.7.1 with the new version number):
   go get github.com/reddit/achilles-sdk@v0.7.1
3. Run a git diff and validate that the changes made to go.mod and go.sum are as expected.
4. Create a PR in the consuming repo with the newly upgraded achilles-sdk version