Add internal callback variant (#438)

Author: bergundy

Diff for: openapi/openapiv2.json

@@ -4653,6 +4653,17 @@
       "type": "object",
       "description": "Trigger for when the workflow is closed."
     },
+    "CallbackInternal": {
+      "type": "object",
+      "properties": {
+        "data": {
+          "type": "string",
+          "format": "byte",
+          "description": "Opaque internal data."
+        }
+      },
+      "description": "Callbacks to be delivered internally within the system.\nThis variant is not settable in the API and will be rejected by the service with an INVALID_ARGUMENT error.\nThe only reason that this is exposed is because callbacks are replicated across clusters via the\nWorkflowExecutionStarted event, which is defined in the public API."
+    },
     "CallbackNexus": {
       "type": "object",
       "properties": {
@@ -6300,6 +6311,9 @@
       "properties": {
         "nexus": {
           "$ref": "#/definitions/CallbackNexus"
+        },
+        "internal": {
+          "$ref": "#/definitions/CallbackInternal"
         }
       },
       "description": "Callback to attach to various events in the system, e.g. workflow run completion."

Diff for: openapi/openapiv3.yaml

@@ -4572,6 +4572,8 @@ components:
       properties:
         nexus:
           $ref: '#/components/schemas/Callback_Nexus'
+        internal:
+          $ref: '#/components/schemas/Callback_Internal'
       description: Callback to attach to various events in the system, e.g. workflow run completion.
     CallbackInfo:
       type: object
@@ -4626,6 +4628,18 @@ components:
       type: object
       properties: {}
       description: Trigger for when the workflow is closed.
+    Callback_Internal:
+      type: object
+      properties:
+        data:
+          type: string
+          description: Opaque internal data.
+          format: bytes
+      description: |-
+        Callbacks to be delivered internally within the system.
+         This variant is not settable in the API and will be rejected by the service with an INVALID_ARGUMENT error.
+         The only reason that this is exposed is because callbacks are replicated across clusters via the
+         WorkflowExecutionStarted event, which is defined in the public API.
     Callback_Nexus:
       type: object
       properties:

Diff for: temporal/api/common/v1/message.proto

@@ -191,8 +191,18 @@ message Callback {
         map<string, string> header = 2;
     }
 
+    // Callbacks to be delivered internally within the system.
+    // This variant is not settable in the API and will be rejected by the service with an INVALID_ARGUMENT error.
+    // The only reason that this is exposed is because callbacks are replicated across clusters via the
+    // WorkflowExecutionStarted event, which is defined in the public API.
+    message Internal {
+        // Opaque internal data.
+        bytes data = 1;
+    }
+
     reserved 1; // For a generic callback mechanism to be added later.
     oneof variant {
         Nexus nexus = 2;
+        Internal internal = 3;
     }
 }