use native fields dataInput and dataOutput

Signed-off-by: Hongchao Deng <[email protected]>

design/resource-dependency.md

@@ -132,47 +132,35 @@ To achieve this, we propose:
           fieldPath: status.connSecret
     ```
 
-2. Add a field `valueFrom.dataOutputName` in Component ParameterValue to specify the dependency on data outputs:
+2. Add a field `dataInputs` in Component configuration to specify a data input:
 
     ```yaml
-    parameterValues:
-    - name: <parameter-name>
-      valueFrom:
+    dataInputs:
+    - valueFrom:
         dataOutputName: <dataoutput-object-name>
+      toFieldPaths: <field-paths-to-fill>
     ```
 
     For example, web app's dependency on RDS's database secret could be specified as:
 
     ```yaml
-    kind: Component
-    metadata:
-      name: my-web
-    spec:
-      workload:
-        kind: MyWorkload
-        metadata:
-          name: my-web
-      parameters:
-      - name: database-secret # workload's fieldPaths needs to be filled
-        fieldPaths:
-        - spec.connSecret
-    ---
-
     kind: ApplicationConfiguration
     spec:
       components:
+      - componentName: my-rds
+        dataOutputs:
+        - name: mysql-conn-secret
+          fieldPath: status.connSecret
+
       - componentName: my-web
-        parameterValues:
-        - name: database-secret
-          valueFrom:
+        dataInputs:
+        - valueFrom:
             # Specify the dependency on a data output.
             # The component's workload won't be created until the data output has returned value to fill workload's fieldPaths. 
             dataOutputName: mysql-conn-secret
+          toFieldPaths:
+          - "spec.connSecret"
 
-      - componentName: my-rds
-        dataOutputs:
-        - name: mysql-conn-secret
-          fieldPath: status.connSecret
     ```
 
     In this case, the OAM runtime will automatically build a dependency from `my-web` to `my-rds`.
@@ -199,17 +187,7 @@ To achieve this, we propose:
       connSecret: mysql-conn # patched by OAM runtime
     ```
 
-3. Similary, add fields `dataOutputs` and `parameters` in Trait configuration to specify the dependency on data output objects.
-
-    ```yaml
-    parameters:
-    - valueFrom:
-        dataOutputName: <dataoutput-object-name>
-      toFieldPaths: <field-paths-to-fill>
-    dataOutputs:
-    - name: <dataoutput-name>
-      fieldPath: <object-field-path>
-    ```
+3. Similary, add fields `dataOutputs` and `dataInputs` in Trait configuration to specify the dependency on data output objects.
 
     For example, we have an etcd backup trait that relies on the data output from an etcd cluster resource.
     We can specify it as:
@@ -229,7 +207,7 @@ To achieve this, we propose:
             kind: EtcdBackup
             metadata:
               name: my-etcd-backup
-          parameters:
+          dataInputs:
           - valueFrom: # An EtcdBackup trait has dependency on some DataOutput to fill its fields.
               dataOutputName: etcd-conn-secret
             toFieldPaths:
@@ -247,10 +225,17 @@ To achieve this, we propose:
 ### Generic core engine consideration
 
 The design of resource dependency is a pretty generic engine that works for any k8s resources.
-Even though we use OAM native fields like `Parameters` or `Outputs` fields, those are just representation layer.
+Even though we use OAM native fields like `dataInputs` or `dataOutputs` fields, those are just representation layer.
 The underlying dependency engine along with the DataInput and DataOutput model is the core implementation,
 which should be generic enough to convert or adopt future concepts or fields.
 
+
+## Impact to existing system
+
+This proposal is additional to existing OAM runtime. It would not affect any existing deployments.
+
+If dataOutputName in a data input doesn't match any name of the data outputs, it would fail the deployment.
+
 ### Spec upgrade path consideration
 
 Initially the feature will be experimental. It might change iteratively.
@@ -290,19 +275,17 @@ In this section we are providing more solution examples for dependency use cases
         kind: MyWorkload
         metadata:
           name: my-web
-      parameters:
-      - name: database-secret
-        fieldPaths: ["spec.connSecret"]
     ---
 
     kind: ApplicationConfiguration
     spec:
       components:
       - componentName: my-web
-        parameterValues:
-        - name: database-secret
-          valueFrom:
+        dataInputs:
+        - valueFrom:
             dataOutputName: mysql-conn-secret
+          toFieldPaths:
+          - "spec.connSecret"
       - componentName: my-rds
         dataOutputs:
           - name: mysql-conn-secret
@@ -318,6 +301,10 @@ In this section we are providing more solution examples for dependency use cases
     spec:
       components:
       - componentName: my-web
+        dataInputs:
+        - fieldPaths: [] # This data input is for ordering purpose only
+          valueFrom:
+            dataOutputName: my-secret-binding
         traits:
         - trait:
             apiVersion: core.oam.dev/v1alpha1
@@ -334,15 +321,3 @@ In this section we are providing more solution examples for dependency use cases
             - name: my-secret-binding
               fieldPath: status.ready
     ```
-
-    Component:
-
-    ```yaml
-    kind: Component
-    metadata:
-      name: my-web
-    spec:
-      parameters:
-      - name: my-secret-binding
-        fieldPaths: [] # This parameter is for ordering purpose only
-    ```