APPC LCM Actor 

Overview of APPC LCM Actor 

ONAP Policy Framework enables APPC as one of the supported actors. The APPC LCM Actor contains operations supporting both the LCM interface and the legacy interface. As such, this actor supersedes the APPC Legacy actor. Its sequence number is lower than the APPC Legacy actor’s sequence number, which ensures that it is loaded first.

APPC Legacy uses a single DMaaP topic for both requests and responses. The class(es) supporting this interface are described in APPC Legacy Actor. The APPC LCM Actor only supports the APPC Legacy operation, ModifyConfig.

The APPC LCM interface, on the other hand, uses two DMaaP topics, one to which requests are published, and another from which responses are received. Similar to the legacy interface, APPC LCM may generate more than one response for a particular request, the first response simply indicating that the request was accepted, while the second response indicates completion of the request.

For each request, a unique sub-request ID is generated. This is used to match the received responses with the published requests. (APPC LCM also has a “correlation-id” field, which could potentially be used to match the response to the request, but apparently APPC LCM has not implemented that capability yet.)

All APPC LCM operations are currently supported by a single java class, AppcLcmOperation, which is responsible for populating the request structure appropriately. This class is derived from BidirectionalTopicOperation.

The remainder of this discussion describes the operations that are specific to APPC LCM.

Request 

CommonHeader 

The “common-header” field in the request is built by policy.

“common-header” field name	type	Description
sub-request-id	string	Generated by Policy. Is a UUID and used internally by policy to match the response with the request.
request-id	string	Inserted by Policy. Maps to the UUID sent by DCAE i.e. the ID used throughout the closed loop lifecycle to identify a request.
originator-id	string	Copy of the request-id.

Action 

The “action” field uniquely identifies the operation to perform. Currently, the following operations are supported:

Restart
Rebuild
Migrate
ConfigModify

The valid operations are listed in AppcLcmConstants. These are the values that must be specified in the policy. However, before being stuffed into the “action” field, they are converted to camel case, stripping any hyphens, and translating the first character to upper case, if it isn’t already.

Action Identifiers 

Currently, the “action-identifiers” field contains only the VNF ID, which should be the targetEntity specified within the ControlLoopOperationParams.

Payload 

The “payload” field is populated based on the payload specified within the ControlLoopOperationParams. Unlike the APPC Legacy operations, which inject POJOs into the “payload” field, the APPC LCM operations simply encode the entire parameter payload into a JSON string, and then place the encoded string into the “payload” field of the request.

Examples 

Suppose the ControlLoopOperationParams were populated as follows:

{
    "actor": "APPC",
    "operation": "Restart",
    "targetEntity": "my-target",
    "payload": {
        "my-key-A": "hello",
        "my-key-B": "world"
    },
    "context": {
        "event": {
            "requestId": "664be3d2-6c12-4f4b-a3e7-c349acced200"
        }
    }
}

An example of a request constructed by the actor using the above parameters, published to the APPC LCM request topic:

{
  "version": "2.0",
  "rpc-name": "restart",
  "correlation-id": "664be3d2-6c12-4f4b-a3e7-c349acced200-8c4c1914-00ed-4be0-ae3b-49dd22e8f461",
  "type": "request",
  "body": {
    "input": {
      "common-header": {
        "timestamp": "2020-05-14T19:19:32.619890900Z",
        "api-ver": "2.00",
        "originator-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "request-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "sub-request-id": "8c4c1914-00ed-4be0-ae3b-49dd22e8f461",
        "flags": {}
      },
      "action": "Restart",
      "action-identifiers": {
        "vnf-id": "my-target"
      },
      "payload": "{\"my-key-A\":\"hello\", \"my-key-B\":\"world\"}"
    }
  }
}

An example initial response received from the APPC LCM response topic:

{
  "body": {
    "output": {
      "common-header": {
        "timestamp": "2020-05-14T19:19:32.619897000Z",
        "api-ver": "5.00",
        "originator-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "request-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "sub-request-id": "8c4c1914-00ed-4be0-ae3b-49dd22e8f461",
        "flags": {}
      },
      "status": {
        "code": 100,
        "message": "Restart accepted"
      }
    }
  },
  "version": "2.0",
  "rpc-name": "restart",
  "correlation-id": "664be3d2-6c12-4f4b-a3e7-c349acced200-1",
  "type": "response"
}

An example final response received from the APPC LCM on the same response topic:

{
  "body": {
    "output": {
      "common-header": {
        "timestamp": "2020-05-14T19:19:32.619898000Z",
        "api-ver": "5.00",
        "originator-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "request-id": "664be3d2-6c12-4f4b-a3e7-c349acced200",
        "sub-request-id": "8c4c1914-00ed-4be0-ae3b-49dd22e8f461",
        "flags": {}
      },
      "status": {
        "code": 400,
        "message": "Restart Successful"
      }
    }
  },
  "version": "2.0",
  "rpc-name": "restart",
  "correlation-id": "664be3d2-6c12-4f4b-a3e7-c349acced200-1",
  "type": "response"
}

Configuration of the APPC LCM Actor 

The following table specifies the fields that should be provided to configure the APPC LCM actor.

Field name	type	Description
sinkTopic	string	Name of the topic to which the request should be published.
sourceTopic	string	Name of the topic from which the response should be read. This must not be the same as the sinkTopic.
timeoutSec	integer (optional)	Maximum time, in seconds, to wait for a response to be received on the topic.

The individual operations are configured using these same field names. However, all of them are optional, as they inherit their values from the corresponding actor-level fields. That being said, the APPC Legacy operation(s) use a different topic than the APPC LCM operations. As a result, the sink and source topics should be specified for each APPC Legacy operation supported by this actor.