CPS-455 - Getting issue details... STATUS


Purpose of spike

The purpose of this spike is to investigate how fields and depth can be implemented and used in conjunction with Restconf to gather attributes from xNFs and be able to determine the depth of information retrieved.

RESTConf defines 'fields' and 'depth' parameters to control the output of a get or query request.

See https://tools.ietf.org/id/draft-ietf-netconf-restconf-07.xml and https://datatracker.ietf.org/doc/html/rfc8040#section-4.8.3


turing-machine.yang 
module turing-machine {

  namespace "http://example.net/turing-machine";

  prefix "tm";

  description
    "Data model for the Turing Machine.";

  revision 2013-12-27 {
    description
      "Initial revision.";
  }

  /* Typedefs */

  typedef tape-symbol {
    type string {
      length "0..1";
    }
    description
      "Type of symbols appearing in tape cells.

       A blank is represented as an empty string where necessary.";
  }

  typedef cell-index {
    type int64;
    description
      "Type for indexing tape cells.";
  }

  typedef state-index {
    type uint16;
    description
      "Type for indexing states of the control unit.";
  }

  typedef head-dir {
    type enumeration {
      enum left;
      enum right;
    }
    default "right";
    description
      "Possible directions for moving the read/write head, one cell
       to the left or right (default).";
  }

  /* Groupings */

  grouping tape-cells {
    description
      "The tape of the Turing Machine is represented as a sparse
       array.";
    list cell {
      key "coord";
      description
        "List of non-blank cells.";
      leaf coord {
        type cell-index;
        description
          "Coordinate (index) of the tape cell.";
      }
      leaf symbol {
        type tape-symbol {
          length "1";
        }
        description
          "Symbol appearing in the tape cell.

           Blank (empty string) is not allowed here because the
           'cell' list only contains non-blank cells.";
      }
    }
  }

  /* State data and Configuration */

  container turing-machine {
    description
      "State data and configuration of a Turing Machine.";
    leaf state {
      type state-index;
      config "false";
      mandatory "true";
      description
        "Current state of the control unit.

         The initial state is 0.";
    }
    leaf head-position {
      type cell-index;
      config "false";
      mandatory "true";
      description
        "Position of tape read/write head.";
    }
    container tape {
      config "false";
      description
        "The contents of the tape.";
      uses tape-cells;
    }
    container transition-function {
      description
        "The Turing Machine is configured by specifying the
         transition function.";
      list delta {
        key "label";
        unique "input/state input/symbol";
        description
          "The list of transition rules.";
        leaf label {
          type string;
          description
            "An arbitrary label of the transition rule.";
        }
        container input {
          description
            "Input parameters (arguments) of the transition rule.";
          leaf state {
            type state-index;
            mandatory "true";
            description
              "Current state of the control unit.";
          }
          leaf symbol {
            type tape-symbol;
            mandatory "true";
            description
              "Symbol read from the tape cell.";
          }
        }
        container output {
          description
            "Output values of the transition rule.";
          leaf state {
            type state-index;
            description
              "New state of the control unit. If this leaf is not
               present, the state doesn't change.";
          }
          leaf symbol {
            type tape-symbol;
            description
              "Symbol to be written to the tape cell. If this leaf is
               not present, the symbol doesn't change.";
          }
          leaf head-move {
            type head-dir;
            description
              "Move the head one cell to the left or right";
          }
        }
      }
    }
  }

  /* RPCs */

  rpc initialize {
    description
      "Initialize the Turing Machine as follows:

       1. Put the control unit into the initial state (0).

       2. Move the read/write head to the tape cell with coordinate
          zero.

       3. Write the string from the 'tape-content' input parameter to
          the tape, character by character, starting at cell 0. The
          tape is othewise empty.";
    input {
      leaf tape-content {
        type string;
        default "";
        description
          "The string with which the tape shall be initialized. The
           leftmost symbol will be at tape coordinate 0.";
      }
    }
  }

  rpc run {
    description
      "Start the Turing Machine operation.";
  }

  rpc run-until {
    description
      "Start the Turing Machine operation and let it run until it is halted
       or ALL the defined breakpoint conditions are satisfied.";
    input {
      leaf state {
        type state-index;
        description
          "What state the control unit has to be at for the execution to be paused.";
      }
      leaf head-position {
        type cell-index;
        description
          "Position of tape read/write head for which the breakpoint applies.";
      }
      container tape {
        description
          "What content the tape has to have for the breakpoint to apply.";
        uses tape-cells;
      }
    }
    output {
      leaf step-count {
        type uint64;
        description
          "The number of steps executed since the last 'run-until' call.";
      }
      leaf halted {
        type boolean;
        description
          "'True' if the Turing machine is halted, 'false' if it is only paused.";
      }
    }
  }

  /* Notifications */

  notification halted {
    description
      "The Turing Machine has halted. This means that there is no
       transition rule for the current state and tape symbol.";
    leaf state {
      type state-index;
      mandatory "true";
      description
        "The state of the control unit in which the machine has
         halted.";
    }
  }

  notification paused {
    description
      "The Turing machine has reached a breakpoint and was paused.";
    leaf state {
      type state-index;
      mandatory "true";
      description
        "State of the control unit in which the machine was paused.";
    }
    leaf head-position {
      type cell-index;
      mandatory "true";
      description
        "Position of tape read/write head when the machine was paused.";
    }
    container tape {
      description
        "Content of the tape when the machine was paused.";
      uses tape-cells;
    }
  }
}


turing-machine response 
{
    "turing-machine": {
        "transition-function": {
            "delta": [
                {
                    "label": "separator",
                    "input": {
                        "state": 0,
                        "symbol": "0"
                    },
                    "output": {
                        "state": 1,
                        "symbol": "1"
                    }
                },
                {
                    "label": "write separator",
                    "input": {
                        "state": 2,
                        "symbol": "1"
                    },
                    "output": {
                        "state": 3,
                        "symbol": "0",
                        "head-move": "left"
                    }
                },
                {
                    "label": "right summand",
                    "input": {
                        "state": 1,
                        "symbol": "1"
                    }
                },
                {
                    "label": "final step",
                    "input": {
                        "state": 3,
                        "symbol": ""
                    },
                    "output": {
                        "state": 4
                    }
                },
                {
                    "label": "go home",
                    "input": {
                        "state": 3,
                        "symbol": "1"
                    },
                    "output": {
                        "head-move": "left"
                    }
                },
                {
                    "label": "right end",
                    "input": {
                        "state": 1,
                        "symbol": ""
                    },
                    "output": {
                        "state": 2,
                        "head-move": "left"
                    }
                },
                {
                    "label": "left summand",
                    "input": {
                        "state": 0,
                        "symbol": "1"
                    }
                }
            ]
        }
    }
}


Assumptions

#AssumptionNotes
1

rests bundle is enable by default


2

node has been mounted


Open Issues & Decisions

#QuestionAnswer
1When field function is used to list attributes in child will the parent still be part of output? Yes if we do not specifically use delta=separator/input?fields=state
2When not supplied with the module, if one match is found then we can insert the module. If more than one submodule is found with the same top-level element then it becomes ambiguous and cannot be resolved. The system will throw an exception in the scenario where more then one submodule


The capabilities of both parameters as defined by RESTConf

Fields

The "fields" query parameter is used to optionally identify data nodes within the target resource to be retrieved in a GET method. The client can use this parameter to retrieve a subset of all nodes in a resource.

  • ";" is used to select multiple nodes. For example, to retrieve only the "genre" and "year" of an album, use: "fields=genre;year".
  • Parentheses are used to specify sub-selectors of a node. For example, to retrieve only the "label" and "catalogue‑number" of an album, use: "fields=admin(label;catalogue‑number)".
  • "/" is used in a path to retrieve a child node of a node. For example, to retrieve only the "label" of an album, use: "fields=admin/label".
  • This parameter is only allowed for GET methods on api, datastore, and data resources. A 400 Bad Request error is returned if used for other methods or resource types.

Fields Syntax

Syntax & examples
'fields=' ( <module-name> ':' )? <container-name> ( '(' <leaf-name> ( ',' <leaf-name> )* ')' )? 
          ( '/' ( <module-name> ':' )? <container-name> ( '(' <leaf-name> ( ',' <leaf-name> )* ')' )? )*

fields=/shops
fields=/shops/shop
fields=/shops/shop(postal-code,town)
fields=bookstore:/shops/shop
fields=bookstore:/shops/bookstore:shop(postal-code,town)
fields=bookstore:/shops/shop(postal-code,town)/bookmodule:book(title)

*<module-name> ':' is compulsory when 'changing' into a different  module from the parent node


Depth

The "depth" parameter is used to specify the number of nest levels returned in a response for a GET method. The first nest-level consists of the requested data node itself. Any child nodes which are contained within a parent node have a depth value that is 1 greater than its parent.

  • The value of the "depth" parameter is either an integer between 1 and 65535, or the string "unbounded". "unbounded" is the default.
  • This parameter is only allowed for GET methods on API, datastore, and data resources. A 400 Bad Request error is returned if it used for other methods or resource types.
  • By default, the server will include all sub-resources within a retrieved resource, which have the same resource type as the requested resource. Only one level of sub-resources with a different media type than the target resource will be returned.


Depth Example

http://localhost:8282/rests/data/network-topology:network-topology/topology=topology-netconf/node=PNFDemo/yang-ext:mount/turing-machine:turing-machine/transition-function?depth=1


The support/limitations of both parameters as implemented by the 'rests' ODL module interface (SDN-C)

The "rests" odl interface supports fields and depth parameters 

rests interface supports application/yang-data+json format

The feasibility/cost of NCMP 'translating' a fields-option without module information 

The feasibility/cost of NCMP 'translating' a fields-option without module information into a RESTConf compatible fields value. High level user story view of cost.

Alternatives

  1. Assume that the query is in one module and no module information is required - cost 0 but won't always work
  2. Insert module information at the start and each transition of module - might lead to unnecessarily long fields section
  3. Insert module information for each element - nicest option


Cost alternative three

  1. Combine the resource path and the fields path into a 'target' path
    requires new interface/REST method on CPS core (assuming there is an anchor with this schema-set)
  2. Walk schema context and check the module for each element
    Throw exception when more than one solution is encountered
  3. Insert module name where needed


Estimate: 1 or 2 user stories (1 or 2 weeks work)


The feasibility/cost of support a 'depth' parameter for CPS cached data and/or ONAP DMI Plugin


  • At the moment we have code to to include all or no descendants


Estimate: 1 user story (1-2 days to modify existing all-or-nothing approach)


Interaction Between Fields & Depth Parameters


Note: Depth can be any value .> 0. However, all details above field in question will be added to output



Note: field take precedence so adding depth=2 is the same as depth=1



Fields with module examples







Video of Demo

zoom_0.mp4


Setting up local netconf-pnp-simulator & SDNC environment

  1. Run docker load -i image.tar to unpack netconf docker image v2.8.6
  2. Unzip certs.tar to same folder as docker-compose.yml (SDNC docker)
  3. Unpack sim.zip
  4. Run docker-compose up -d
  5. Run sim/docker-compose -f docker-compose-sim.yml up -d (netconf-pnp-simulator docker)
  6. To access local SDNC/ODL use -  http://localhost:8282/apidoc/explorer/index.html
    • Credentials  : - admin / Kp8bJ4SXszM0WXlhak3eHlcse2gAw84vaoGGmJvUy2U


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