Analysis of Get a Node API

1 Problem Statement
2 Comparision with Query Node API
3 Associated problems
- 3.1 Impact on Delta Feature
4 Proposed Solution

Use Discussion notes to capture meeting items, assign owners, and track actions and decisions.

Date	Item	Owner	Notes	Relevant Links

Date	Item	Owner	Notes	Relevant Links
Sep 25, 2024	Propose solution and discuss with community	@Arpit Singh	Proposal discussed with community and decided to implement the changes as proposed below.	Analysis of Get a Node API \| Proposed Solution
Dec 5, 2024	Approved to implement changes in get node Api based on the proposal.	@Rudrangi Anupriya to take over the implementation	Create ticket for Get a Node API Development Demo

Problem Statement

When a list is fetched using Get a node API then instead of returning a JSON list containing n-number of list items, the API returns each list item as individual JSON object. And each of these JSON objects have same name as the list name.

For example: if there is a list named books, with xpath /bookstore/categories[@code=4]/books, containing 2 books named Book 1 and Book 2.

[
    {
        "categories": {
            "code": "4",
            "name": "Computing",
            "books": [
                {
                    "title": "Book 1",
                    "lang": "N/A",
                    "price": 11,
                    "editions": [2009]
                },
                {
                    "title": "Book 2",
                    "lang": "German",
                    "price": 39,
                    "editions": [2007, 2013, 2021]
                }
            ]
        }
    }
]

When fetching this list using get a node API, we get a parent JSON list containing two individual JSON objects. Where each JSON object is named books and under these two objects we have the books named book1 and book 2.

[
    {
        "books": {
            "title": "Book 1",
            "lang": "N/A",
            "price": 11,
            "editions": [2009]
        }
    },
    {
        "books": {
            "title": "Book 2",        
            "lang": "German",
            "price": 39,
            "editions": [2007, 2013, 2021]
        }
    }
]

This output makes the JSON inconsistent from the original data and difficult to work with because when fetching a list node, it is expected to get the entire list as is rather than each list item being returned as individual JSON objects.

The expected output should be of the following format

[
  {
    "books": [
      {
            "title": "Book 1",
            "lang": "N/A",
            "price": 11,
            "editions": [2009]
      },
      {
            "title": "Book 2",        
            "lang": "German",
            "price": 39,
            "editions": [2007, 2013, 2021]
      }
    ]
  }
]

Comparision with Query Node API

When the same list node is accessed using Query a Node API, we get the same response as described above where each list item is fetched as individual JSON object with same name as the list.

Associated problems

Impact on Delta Feature

The inconsistency described above extends to CPS Delta feature when using it to compare list nodes.

This is because the delta feature shares the logic/code of Get a Node API to fetch the data nodes from the data base before generating the delta.

So, when comparing JSON containing a list, to a list fetched from the data base, an inconsistent delta is generated because logically the JSON list supplied as input by the user is compared to the first JSON object of the same name, returned by the code. This comparison can be imagined as follows:

JSON list provided by user	JSON objects fetched from database

JSON list provided by user	JSON objects fetched from database

Proposed Solution

Based on the discussions in the community call dated 25th September 2024: The Get a Node API should return the list as is instead of returning each list item as an individual JSON objects. This is because when returning each list item as individual JSON object the data returned deviates and differs from what was originally stored in the data base, that is a singular list.

This leads to inconsistent data being returned by the API which in turn causes problems when trying to use the data.

ONAP Wiki