common-go-libs

# WSO2 APK - Common go libs

This guide has information to setup common types for development and tasks for k8s operator development.

## Prerequisites

The following should be installed in your dev machine.

- [Gradle](https://gradle.org/install/) >= 7.5.1 version
- [Docker](https://docs.docker.com/engine/install/ubuntu/) >= 17.03 version
- [Golang](https://go.dev/doc/install) >= 1.19.0 version
- [Revive](https://github.com/mgechev/revive#installation) latest version
- [Kubebuilder](https://book.kubebuilder.io/quick-start.html#installation)

## Setting up

1. Clone the `wso2/apk` repository and navigate into adapter directory in home directory of the cloned tree.

    ```bash
    git clone https://github.com/wso2/apk.git
    ```

2. Check whether you can build the project without running into any issues.

    ```
    gradle build
    ```

3. If you ran into any issue first check whether the [prerequisites](#prerequisites) are satisfied.

## Operator

Since the adapter component uses Kubebuilder framework for operator development, when doing some tasks not listed below then first place to check is the [Kubebuilder documentation](https://book.kubebuilder.io/).

Code for the operator lies in `{PROJECT_HOME}/adapter/internal/operator`. This will be referred as `OPERATOR_HOME` in the upcoming sections.  

Following are some tasks with the steps that a developer might do in operator development:

- [Adding a new Kind](#adding-a-new-kind)
- [Adding a new property to an existing Kind](#adding-a-new-property-to-an-existing-kind)
- [Adding validating and defaulting logic](#adding-validating-and-defaulting-logic)

### Adding a new Kind

1. Decide what the k8s resource group will be depending on whether the CRD is for the control-plane or for the data-plane.

    | Plane  | k8s group |
    | ------------- | ------------- |
    | Data Plane  | dp  |
    | Control Plane  | cp  |

2. Decide the version for the CRD. Current version for all the CRDs are used as `v1alpha1`. 


3. Let's say we want a new Kind called `APIPolicy` for data plane then run the following Kubebuilder command to scaffold out the new kind.

    ```bash
    kubebuilder create api --group dp --version v1alpha1 --kind APIPolicy
    ```

4. This will prompt for creating the resource. Respond yes for that since we need to generate the CRD for it.

    ```bash
    Create Resource [y/n]
    y
    ```

5. Next it will prompt for generating the boilerplate code for a controller, respond yes to it. As we are using a single controller in the current architecture. If your CR changes can be mapped to a `API` kind change event then you can delete the controller file. But, there might be cases you want a separate controller, then keep the generated controller file and add the code there.

    ```bash
    Create Controller [y/n]
    n
    ```

    Now new scaffold files/changes should be available in following directory structure:

    ```bash
    {OPERATOR_HOME}
    ├── PROJECT
    ├── apis
    │   ├── cp
    │   │   └── v1alpha1
    │   │       ├── ...
    │   │       └── ...
    │   └── dp
    │       └── v1alpha1
    |           ├── ...
    │           ├── apipolicy_types.go
    │           └── zz_generated.deepcopy.go
    .
    .
    ```


6. The `apipolicy_types.go` contains the go struct representing the our example `APIPolicy` kind. You need to fill in the `APIPolicySpec` and `APIPolicyStatus` structs as per the needs.

    ```go
    // APIPolicySpec defines the desired state of APIPolicy
    type APIPolicySpec struct {
        // +kubebuilder:validation:MinLength=4
        Type      string                          `json:"type,omitempty"`
        ...
        ...
        TargetRef gwapiv1a2.PolicyTargetReference `json:"targetRef,omitempty"`
    }
    ```

    Here we have set the `Type` property to be required by adding `// +kubebuilder:validation:MinLength=4` [marker](https://book.kubebuilder.io/reference/markers/crd-validation.htm).


7. Finally do the gradle build and check whether the build is successful.

    ```bash
    gradle build
    ```

8. Commit changes to github.

9. To make the CRD and other resource changes affect, you need to move the k8s resources to the helm chart in `PROJECT_HOME/helm-charts` directory:

    - Append new rules to the `ClusterRole` in `helm-charts/templates/serviceAccount/apk-cluster-role.yaml`.

        ```yaml
        - apiGroups: ["dp.wso2.com"]
          resources: ["apipolicies"]
          verbs: ["get","list","watch","update","delete","create"]
        - apiGroups: ["dp.wso2.com"]
          resources: ["apipolicies/finalizers"]
          verbs: ["update"]
        - apiGroups: ["dp.wso2.com"]
          resources: ["apipolicies/status"]
          verbs: ["get","patch","update"]
        ```