Use the controller-runtime to replace the existing Watch and Handle APIs

[hasbro17]

The controller-runtime project is a set of libraries used to build controllers.

We've been discussing the use of the controller-runtime to refactor and redesign our existing APIs for a while now to resolve a number of design related issues e.g removing global state(#169), reducing the API surface(#160), support watching multiple custom resources(#146) filtering events on predicates (#268)

We'll use this issue to track the work needed for refactoring the SDK's informer and client APIs to use the controller-runtime.

[CSdread]

Is there a design document for this yet? or will it be hashed out here.

[hasbro17]

@CSdread Sorry for the delayed response. There's no design document yet.

Right now we're trying out a basic implementation of the SDK that uses controller-runtime.
Specifically this entails overhauling the SDK generator pkg to use the controller-tools generators so it can scaffold an operator project that uses the controller-runtime directly (without any abstractions or wrappings from the SDK).
An example of such a project structure would be something like https://github.com/kubernetes-sigs/controller-tools/tree/master/test
Most likely that will be a separate branch so the reviewers can try it out.

Based on that we can have a design doc or further discussion on how much(if at all) the SDK should encapsulate the controller-runtime library to provide its own APIs. That's still a WIP and I'll update here once we have a reference implementation.

[hasbro17]

Tracking the reference implementation for the controller-runtime based SDK in the branch refactor/controller-runtime

TODO:

• Make code-generator(only deepcopy) work with multiple apis under pkg/apis 5eb5814
• Refactor operator-sdk new <project>
  • Only scaffolds a new project with the main program at pkg/cmd/manager/main.go
  • Scaffolds everything except pkg/apis/<group>/<version> pkg/controller/<kind>
  • *: add codegen for apis.go #485 *: add codegen for pkg/controller/controller.go #487 *: add codegen for pkg/build/Dockerfile #488 *: add codegen for pkg/build/build.sh #490 *: add codegen for deploy/role_bind.yaml #505 *: add codgen for base deploy/role.yaml #506 *: add codegen for deploy/operator.yaml #511
• Cmd for adding a new api
  • operator-sdk add api —kind=<Kind> —api-version=<APIVersion>
  • Generates pkg/apis/<group>/<version> *: add operator-sdk add api command #491 add api: add new type, generate crd and example cr #504
• Cmd for adding a new controller *: add controller command and templates #514
  • operator-sdk add controller —kind=<Kind> —api-version=<APIVersion>
    • Generates pkg/controller/<kind>
• Update the docs, user-guide and examples, for the new commands and project structure
  • Update the README *: update README and fix templates and commands #542
  • Update the memcached-operator user-guide example *: update user-guide and memcached-operator example #551
  • Update the memcached-operator example in the operator-sdk-samples repo as a separate branch. See the updated memcached-operator branch
• Update e2e tests and operator-sdk test according to the changes in the deployment manifests and project structure. *: update test framework and related changes from master #579
• Remove unused sdk pkgs for the dynamic client, handler, generator
• Migration docs for existing projects to update to v0.1.0 and use the controller-runtime pkgs.
  • Migration guide that goes over an example on manually updating the project structure, moving the reconcile code(pkg/stub/handler to pkg/controller) and updating pkg/apis. doc: add migration guide #653