References

CPS-390 - Getting issue details... STATUS

RESTful API Design Specification

Issues and Decisions

#	Issue	Notes	Decision
1	How will hostname and port be provided when dmiPlugin register itself and its list of cmHandles with NCMP	The team thinks that the information should instead be provided in the form of a ‘host-name’ and a ‘port’  (there was some debate on service-name v. host-name but it was settled on host-name) e.g. "dmiPlugin" : { <host-name>,  <port> } Where the host-name is unique. (the DB might assign an internal unique ID for each entry but that is just for indexing and x-referencing in a relation DB and this ID is not to be used/ exposed externally)	Instead of using ‘host-names’ and ‘ports’ parameters between java applications when in the cloud all we need is ‘service-names’ . The mapping of service-names to hosts and ports is done as part of the cloud configuration, in our case Kubernetes. And these are dynamic! The client application can then use a simple dns-lookup to connect to an instance of the service. Using service names also allows any plugin to use implement scaling as they see fit e.g. partitioning For the ONAP DMI Plugin which initial have only 1 instance we can simply hard-code the service-name and us the same name in the Kubernetes configuration e.g. “onap.cps.dmiPlugin"
2	Additional information in request body duplicates cmHandleId this is redundant information	Suggested to remove from request body to avoid possible error scenarios.	Only the one with the additionalInformation is needed and remove body
3	No need for Sync method, this is basic standard read operation at the root level for that cmHandle
4	Use include 'location' property when request yang-module sources	Suggestion: do include it in the request but allow dmiPlugin to decide to use it or now. Location (this leaf is called schema in older RFC7895) is not mandatory to support in YANG library and nodes may not include it. Another alternative presumably used also by ODL itself is the <get-schema> RPC. The key difference is that the YANG module definition is sent directly over the NETCONF channel, not requiring separate file servers and clients. So this is maybe one more reason that the ONAP DMI plugin currently doesn’t need the location attribute.	Location is not needed for any plugin and could only lead to ambiguity therefore will NOT be included in this request
5	Inconsistent use of "Operation" and/or HTTP Methods to distinguish write operations	Currently this page proposes to use "Operation=update" request body parameter for restconf "Replace" and "Patch" operations and use the HTTP (RESTFul) operation to distinguish between them. It also proposes to use PUT  HTTP for Read and Delete operations Basically a very confusing an unintuitive use of HTTP operations to distinguish ambiguous operations that instead easily could be defined by just using the 'operation' field in the request body.	Proposal Toine: For Consistent (restful) design I would suggest to think as the operation to DMI-Plugin (always with body) as "creating a new order to do something" toward DMI-Plugin. Ie always a HTTP POST (or PUT?) operation. The "operation " in the body can simple be extended to include both "update" and "patch" as required. If the 'operation' is NOT supplied "read" wil be assumed as the default operation See also CPS-577: Prepare the request from client and send write request to dmi-plugin Proposal agreed by stakeholders in meeting 09 Nov 2021  Only 'POST' method needs to be supported use term 'Update' instead of 'replace'

DMI URI

Below table shows the proposed interface, actual implementation might deviate from this but can be accessed from

• Gerrit Source 
• Read-the-docs: https://docs.onap.org/projects/onap-cps-ncmp-dmi-plugin/en/latest/design.html

DMI URI format to follow below pattern

<OP>dmi/<v{vNumber}>/ch/<cmHandle>/<data|operations|dmiAction>/ds/<datastore>/[rp:]<resourcePath>?<query>

NCPS-NCMP - DMI Plugin Write Request Flow

See CPS-577: Prepare the request from client and send write request to dmi-plugin

Datastore

If the cmhandle metadata indicates that data is not synched in CPS then the request is forwarded to the dmiPlugin

RESTCONF/NETCONF relationship

REST Data API

The DMI APIs for data access are similar to corresponding NCMP APIs. The following list is a summary of the main differences:

1. The URI prefix is /dmi instead of /ncmp.
2. For non-passthrough datastores, the resource path will be converted from cpsPath to RESTConfPath

3. The body for each request will contain additional information and any data provided on the NCMP interface (write operations) will be embedded in a larger JSON structure as described in example below.
   

4. Since all requests will have a message body, in some cases the HTTP method will be different to allow passing data. Thus POST can be used, the actual operation will be read from the body.

Request Format for Data Access

{
  “operation”: “<operation>”,         // Valid operations are: “create”, “read”, “update” and “delete”.
                                      // For update, replace and patch is distinguished by the HTTP method (PUT or PATCH).
  "dataType": "<dataType>",

    “data”: {                           // Embedded data as a String.
    <data>                            // required for create and update operations. Optional filter-data for read-operations
  },

  “cmHandleProperties”: {           // Additional properties for CM handle previously added by DMI plugin and stored in NCMP.
    <properties>
  }
}

DMI Inventory, Model & Data Sync API

 This presentation illustrates the API methods #1, #3 and #4 detailed below

{
  "operation": "read",
    "cmHandleProperties ": {
      "subSystemId": "system-001"
    }
  }
}

Response:  
     "schemas": [
                    {
                      "moduleName": "example-identifier",
                      "revision": "example-version",
                      "namespace": "example-namespace"
                    },
					{
						...
					}
                  ]
                }

{
  "operation": "read",
	"dataType": "application/json",
    "data": {
       "modules": [
        {
          "name": "pnf-sw-upgrade",
          "revision": "2019-12-03"
        }
      ]
    },
    "cmHandleProperties": {
      "subSystemId": "system-001"
    }
}

Response: a list yang module references and source for each

[ {
"name" : "pnf-sw-upgrade",
"revision" : "2019-12-03",
"yang-source": "some-source", {...} ]

GET Request with body

The HTTP libraries of certain languages (notably JavaScript) don’t allow GET requests to have a request body. In fact, some users are surprised that GET requests are ever allowed to have a body.

The truth is that RFC 7231—the RFC that deals with HTTP semantics and content—does not define what should happen to a GET request with a body! As a result, some HTTP servers allow it, and some—especially caching proxies—don’t.

The authors of Elasticsearch prefer using GET for a search request because they feel that it describes the action—retrieving information—better than the POST verb. However, because GET with a request body is not universally supported, the search API also accepts POST requests: }

The same rule applies to any other GET API that requires a request body.
See Elasticsearch details here for more info

yang-patch operations (see rfc8072)

"create", "delete", "insert", "merge", "move", "replace", and "remove"

YANG Data Structure Extensions

https://tools.ietf.org/html/rfc8791

References

Follow principles/patterns of RESTCONF RFC-8040 https://datatracker.ietf.org/doc/html/rfc8040
Follow principles/patterns of yang-patch RFC-8072 https://datatracker.ietf.org/doc/html/rfc8040
Follow principles/patterns of RESTCONF NMDA RFC-8527 https://datatracker.ietf.org/doc/html/rfc8527