CPS-390 - Getting issue details... STATUS

RESTful API Design Specification

Issues and Decisions

1How 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"
2Additional information in request body duplicates cmHandleId this is redundant informationSuggested to remove from request body to avoid possible error scenarios.Only the one with the additionalInformation is needed and remove body
3No need for Sync method, this is basic standard read operation at the root level for that cmHandle

4Use include 'location' property when request yang-module sourcesSuggestion: 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

5Inconsistent use of "Operation" and/or HTTP Methods to distinguish write operationsCurrently 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 (sad) 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-NCMP - DMI - SDNC Request and Response Mapping

Proposal agreed by stakeholders in meeting  

  • Only 'POST' method needs to be supported
  • use term 'Update' instead of 'replace'


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

DMI URI format to follow below pattern


URIMandatory or OptionalDescription
<OP>mandatorythe HTTP method
dmimandatorythe dmi root resource
<v{vNumber}>mandatoryversion of the dmi interface is the target resource URI is the query parameter list
<cmHandle>mandatoryunique (string) identifier of a yang tree instance.
<data|operations|dmiAction>mandatoryyang data, rpc operation or a (non-modeled) dmi action
{datastore}mandatorymandatory datastore
<resourcePath>optionalthe path expression identifying the resource that is
being accessed by the operation. If this field is not
present, then the target resource is the API itself.
<query>optionalthe set of parameters associated with the RESTCONF message;
see Section 3.4 of [RFC3986]. RESTCONF parameters have 
the familiar form of "name=value" pairs. Most query parameters are
optional to implement by the server and optional to use by the client. Each optional query parameter is identified by a URI

NCPS-NCMP - DMI Plugin Write Request Flow

See CPS-NCMP - DMI - SDNC Request and Response Mapping


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



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

request body
  “operation”: “<operation>”,         // Valid operations are: “create”, “read”, “update”, “patch” and “delete”.
  "dataType": "<dataType>",           // e.g. "application/"

    “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.

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

UsecaseREST MethodURI
1Add a data resource for a cmHandlePOST



Content-Type: application/json

"data" payload : yang-data+json

2Delete a data resource for a cmHandlePUT{dmiRoot}/dmi/v1/ch/<cmHandle>/data/ds/ncmp-datastore:running/{resourceIdentifier}
3Patch a data resource for a cmHandlePATCH



Content-Type: application/json

"data" payload : yang-data+json

4Patch multiple child resources for a single cmHandlePATCH


Content-Type: application/json

"data" payload : yang-patch+json

5Execute a yang action on a cmhandle instancePOST


input: {
         "param1Name" :"param1Value”,
          "param2Name" : "param2Value”


Note : If the "action" statement has no "input" section, the request message MUST NOT include a message-body

6Execute an rpc operationPOST

{dmiRoot}/dmi/v1/operations/ch/<cmHandle>/ds/ncmp-datastore:operational/ {module-name}:{action}

{ input: {
            "param1Name" : "param1Value”,
             "param2Name" : "param2Value”
} }

Note: If there is no "input" section, the request MUST NOT include a message-body

7Read a filtered set of data under a data resource for a cmHandlePUT


fieldsRequest a subset of the target
resource contents
8Read data resources with specified fields under a given data resource for a given cmHandlePUT


fieldsRequest a subset of the target
resource contents
9Get data resource with 'fileds' for a cmhandle with a given scope conditionPUT{dmiRoot}/dmi/v1/ch/{cmHandle}/data/ds/ncmp-datastore:operational/{resourcepath}?fields={fields}&scope={scope}
10Read descendant nodes to a given depth for a given cmHandlePUT


depthRequest limited sub-tree depth in
the reply content
If '1' then only immediate resource
is retrieved
If '2' then resource plus next level
resources are retrieved
11Replace data for a CMHandlePUT


{data : {

            .... the complete tree config to be replaced


DMI Inventory, Model & Data Sync API

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

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

*For response output, where applicable the yang-library format and conventions are used 'as is'  or extended

#Use CaseRest MethodURIExample*

Get module set for a cmhandle


Header :
Content-Type: application/json

Request Body
  "operation": "read",
    "cmHandleProperties ": {
      "subSystemId": "system-001"

Response Body
     "schemas": [
                      "moduleName": "example-identifier",
                      "revision": "example-version",
                      "namespace": "example-namespace"

2Get yang module source for a list of modulesPOST


DMI Plugin will make multiple requests to xNF and combine the result in a list

Request Body
  "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

Response Body
[ {
"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


Follow principles/patterns of RESTCONF RFC-8040
Follow principles/patterns of yang-patch RFC-8072
Follow principles/patterns of RESTCONF NMDA RFC-8527

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