add operationJob plugin usage

kuperator_versioned_docs/version-v0.6/manuals/operationjob.md

@@ -10,7 +10,7 @@ Each operational plugin will be presented as a type of `Action` API in Operation
 Additionally, it optionally facilitates seamless integration with the `PodOpsLifecycle` to ensure lossless traffic changes during operations.
 
 # Example
-Following docs will guide you to play with OperationJob, and to implement a demo OperationJob action by plugin.
+Following docs will guide you to play with OperationJob, and to implement OperationJob action plugin.
 
 ## Replace
 ### Prepare Pods
@@ -26,7 +26,7 @@ foo-752sz      1/1     Running   0             41s
 foo-jttd5      1/1     Running   0             41s
 ```
 
-### Create Replace OperationJob
+### Create OperationJob
 The following `operationjob.yaml` file describes a `Replace` OperationJob, which will replace pods in `targets`.
 For each replace operation, a new pod will be created to replace the target pod, which will not be deleted until new pod is **[ServiceAvailable](../concepts/podopslifecycle.md#introduction)**.  
 
@@ -139,7 +139,60 @@ NAME          PROGRESS    AGE
 opj-replace   Succeeded   6m42s
 ```
 
-The ```status.targetDetails[x].extraInfo``` is a key-value string map, which is used to store operate information, such as operation stages, object metadata. 
+The ```status.targetDetails[x].extraInfo``` is a key-value string map, which is used to store operate information for target. 
 Developers can define and utilize specified extraInfos for their action plugins.
 
-## Tutorial
+## Tutorial
+### Action Plugin
+Developers implement and register action plugin, then OperationJob controller is responsible for running it:
+![operationjob-framework](/img/kuperator/manuals/operationjob/operationjob-frame.png)
+Action plugin is formulated as golang adapter `ActionHandler`, which consists 4 idempotent functions:
+- `Setup` sets up action in `AddToMgr`, i.e., watch resources for action, register cache index
+- `OperateTarget` operates what you want to the target pod
+- `GetOpsProgress` gets current operation status of target pod, i.e., "Processing", "Failed" and "Succeeded"
+- `ReleaseTarget` cleans up target pod and operating environment when operation finished or job deleted
+
+```shell
+cat ~/kuperator/pkg/controllers/operationjob/opscore/handler.go
+```
+
+```go
+...
+type ActionHandler interface {
+	// Setup sets up action with manager in AddToMgr, i.e., watch, cache...
+	Setup(controller.Controller, *mixin.ReconcilerMixin) error
+
+	// OperateTarget do real operation to target
+	OperateTarget(context.Context, *OpsCandidate, *appsv1alpha1.OperationJob) error
+
+	// GetOpsProgress returns target's current opsStatus, e.g., progress, reason, message
+	GetOpsProgress(context.Context, *OpsCandidate, *appsv1alpha1.OperationJob) (progress ActionProgress, err error)
+
+	// ReleaseTarget releases the target from operation when the operationJob is deleted
+	ReleaseTarget(context.Context, *OpsCandidate, *appsv1alpha1.OperationJob) error
+}
+```
+
+### Register Action
+Once action plugin is implemented, developers can register it by calling `RegisterAction` before OperationJob controller `AddToMgr`. 
+It consists 3 parameters: 
+- `action`: string, name of action plugin, showed in `spec.action`
+- `hander`: ActionHandler, the implemented adapter
+- `enablePodOpsLifecycle`: bool, if true, target pods will be operated in the manner of **[PodOpsLifecycle](../concepts/podopslifecycle.md)**
+
+```shell
+cat ~/kuperator/pkg/controllers/operationjob/opscore/register.go
+```
+
+```go
+...
+// RegisterAction will register an operationJob action with handler and lifecycleAdapter
+// Note: if enablePodOpsLifecycle=false, this operation will be done directly, ignoring podOpsLifecycle
+func RegisterAction(action string, handler ActionHandler, enablePodOpsLifecycle bool) {...}
+```
+
+### Practice
+OperationJob natively supports Replace action. And Replace ActionHandler is implemented in the bellow folder:
+```shell
+cd ~/kuperator/pkg/controllers/operationjob/replace
+```