Page Comparison

Table of Contents

minLevel	1
maxLevel	4
outline	false
style	none
type	list
printable	true

Panel

panelIconId	1f4a1
panelIcon	:bulb:
panelIconText	💡
bgColor	#E6FCFF

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

...

Date

...

Item

...

Owner

...

Notes

...

Relevant Links

...

09 Aug 2024

...

@someone

...

Action

Problem statement

...

Issues and Decisions

Date

Item

Owner

Notes

1

15 Jan 2025

Proposal discussed in community weekly meeting Configuration Persistence Service Paris Meeting Notes & Recordings

Arpit Singh

Team suggested using exact data node xpath instead of using parent node xpath is a better approach to avoid confusion.

2

Team suggested to have the extra verification step as suggested in RFC-5789 to verify the data exists and no extra data is part of updated payload before performing the PATCH operation

3

To check the impact of suggested changes on performance and NCMP before implementing them

References

Problem statement

The inconsistencies with the CPS Core API: Update node leaves can be summarized as one major scenario, that is, the API performs partial updates update when updating multiple data nodes via in a single request.

This problem can then be split into 2 sub-problems, but in short, we will see that when an attempt is made to update a parent and child node in through a single request is made then, either the parent or the child node will be updated but not both.

And once Once the request is executed, the user is provided with a 200-response code, but when the data is checked after the update operation, it is found that a partial update took takes place.

The problem here is that the user will have a false sense of security that the API executed their request successfully but in reality, only a partial update of data took place in the backend.

The following endpoint is impacted and covered in this document

Code Block
PATCH: /{apiVersion}/dataspaces/{dataspace-name}/anchors/{anchor-name}/nodes

Some key points to consider before understanding the problem’s

The API is limited to updating only one data node at a time, but still the user can send a payload containing multiple updated data nodes.
In order to update a data node, the request accepts the xpath of the parent node. So, if the user wants to update a Node C nested under Nodes A and B, then the xpath in the request will be that of Node B, that is /A/B, because Node B is parent of Node C.

Expand

title	Simple diagram explaining the example above.

Code Block
To update Node C the xpath in request will be of parent node B: "/A/B" Node A └── Node B └── Node C

Scenario 1: API accepts

...

additional information in payload

In order for an update operation to take place the following 2 key parameters are to be provided by the user as part of the request,

Data Node to be updated as JSON/XML payload
Parent node xpath of the Data Node being updated

Going by this approach, an An inconsistency that is was discovered is that the user can send modified/ updated data of the parent node as part of the payload and even though sending data of parent node in payload is incorrect and a user error, the API would still accept the data and perform the a partial update operation.

But So, when the data is verified then it is found out that the API performed a partial update while returning a 200-status code to the user. And in this partial update the changes to parent node are ignored and only the child node is updated.

A more detailed explanation with examples is as follows:

1: The following JSON is the data to be updated. Here we want to update the book titled “Matilda” under parent node categories with code “1”.

Expand

title	Original Data

Code Block
{ "code": 1, "name": "Children", "books": [ { "title": "Matilda", "lang": "English", "editions": [1988, 2000], "price": 20 } ] }

2: In order to Update any leaf associated to book titled “Matilda” the correct xpath and json payload in the request would be as follows:

Expand

title	Correct xpath and JSON payload

parent node xpath: /bookstore/categories[@code=1]

JSON payload:

Code Block
{ "title": "Matilda", "editions":[1988, 2000, 2024], "price": 25 }

data node xpath: /bookstore/categories[@code="1"]/books[@title="Matilda"]

3. But if there is a user induced error where the payload contains the parent node data, then the JSON payload would look as follows:

Expand

title	xpath with incorrect JSON payload

xpath: /bookstore/categories[@code=1]

Incorrect JSON payload:

Code Block

language	none

{
  "code": 1,                      //parent node data should not be in the payload
  "name": "Kids",                      
  "books": [
    {
      "title": "Matilda",
      "editions": [1988, 2000, 2024],
      "price": 25
    }
  ]
}

4. This would result in a partial update of original data as below. Here we can see even though name is updated from Children to Kids. The data when fetched from database after update operationdoes not reflect the change.

Expand

title	Data fetched from DB after partial update

Code Block
{ "code": "1", "name": "Children", //not updated "books": [ { "title": "Matilda", "lang": "English", "editions": [1988, 2000, 2024], //updated "price": 25 //updated } ] }

Proposed Solution for Scenario 1:

The proposed solution is to drop the support for using parent node xpath in the request and instead the exact xpath of the data node being updated should be provided in the request.
- throw an exception when additional data nodes are in the payload
Apart from this based on the RESTful rules, an additional check should be put in place to first fetch the existing data from the database and verify that it exists and is valid before performing the PATCH operation.

Scenario 2: API does not update child nodes

The update node API can only update one data node at a time. Hence if we have 3 nodes such that Node A is the parent node, Node B is child of Node A and Node C is grandchild of Node A.

Then in the following hierarchy if a user wants to update Node B then the correct request would contain the xpath /A with updated data of Node B. But an inconsistency that is was found with in this scenario is that the payload can contain updated data of Node C as well. The API would accept the payload and perform a successful update operation returning a 200-status code. But when the data in the database is verified after the update operation then it is seen that only the data under Node B is updated, whereas the data of Node C remains unchanged.

...

A more detailed explanation is as follows:

1. The following JSON is

...

to be updated. Here we want to update the category `name` from “`Children`” to “`Kids`”.

Expand

title	Original Data

Code Block

language	json

{
  "categories": {
    "code": "1",
    "name": "Children",
    "books": [
      {
	 	"title": "Matilda",
        "lang": "English",
        "price": 200,
        "editions": [1988,2000]
      }
    ]
  }
}

2. In order to Update any leaf associated to category with code “1” the correct parent node xpath and json payload in the request would be as follows:

Expand

title	Correct xpath and JSON payload

parent node xpath: /bookstore

Correct JSON payload:

Code Block
{ "categories": { "code": 1, "name": "Kids" } }

3. But there can be a user induced error where the payload can contain updated/modified data of grandchild nodes under category with code “1”. And the API would still accept the payload and execute the Update operation.

Expand

title	xpath with incorrect JSON payload

parent node xpath /bookstore

Incorrect JSON payload containing the updated grandchild node named books under category with code 1:

Code Block
{ "categories": { "code": 1, "name": "Kids", "books": [ { "title": "Matilda", "price": 20, "editions":[1988, 2000, 2022] } ] } }

4. This would result in a partial update of original data as below. Here we can see only the name is updated from Children to Kids. Whereas leaves of grandchild, that is book titled `Matilda,` remain unchanged, for example `price` is not updated from `200` to `20`

Expand

title	Data fetched from DB after partial update

Code Block
{ "categories": { "code": "1", "name": "Kids", //updated "books": [ { "title": "Matilda", "lang": "English", "price": 200, //not updated "editions": [1988,2000] //not updated } ] } }

Proposed Solution for Scenario 2

Solution 1: Limit the update operation to one Data Node at a time
- throw an exception if more than one data nodes are present in the payload
Solution 2: Add support to update multiple data nodes

Proposed/Accepted Solution

Info
WIP

Version	Old Version 1	New Version Current
Changes made by	Arpit Singh	Arpit Singh
Saved on	Oct 14, 2024	Jan 23, 2025

Versions Compared

Key

Problem statement

Issues and Decisions

References

Problem statement

Some key points to consider before understanding the problem’s

Scenario 1: API accepts

additional information in payload

1: The following JSON is the data to be updated. Here we want to update the book titled “Matilda” under parent node categories with code “1”.

2: In order to Update any leaf associated to book titled “Matilda” the correct xpath and json payload in the request would be as follows:

3. But if there is a user induced error where the payload contains the parent node data, then the JSON payload would look as follows:

4. This would result in a partial update of original data as below. Here we can see even though name is updated from Children to Kids. The data when fetched from database after update operationdoes not reflect the change.

Proposed Solution for Scenario 1:

Scenario 2: API does not update child nodes

1. The following JSON is

to be updated. Here we want to update the category `name` from “`Children`” to “`Kids`”.

2. In order to Update any leaf associated to category with code “1” the correct parent node xpath and json payload in the request would be as follows:

3. But there can be a user induced error where the payload can contain updated/modified data of grandchild nodes under category with code “1”. And the API would still accept the payload and execute the Update operation.

4. This would result in a partial update of original data as below. Here we can see only the name is updated from Children to Kids. Whereas leaves of grandchild, that is book titled `Matilda,` remain unchanged, for example `price` is not updated from `200` to `20`

Proposed Solution for Scenario 2

Proposed/Accepted Solution

Page Comparison

Versions Compared

Key

Problem statement

Issues and Decisions

References

Problem statement

Some key points to consider before understanding the problem’s

Scenario 1: API accepts

additional information in payload

1: The following JSON is the data to be updated. Here we want to update the book titled “Matilda” under parent node categories with code “1”.

2: In order to Update any leaf associated to book titled “Matilda” the correct xpath and json payload in the request would be as follows:

3. But if there is a user induced error where the payload contains the parent node data, then the JSON payload would look as follows:

4. This would result in a partial update of original data as below. Here we can see even though name is updated from Children to Kids. The data when fetched from database after update operationdoes not reflect the change.

Proposed Solution for Scenario 1:

Scenario 2: API does not update child nodes

1. The following JSON is

to be updated. Here we want to update the category name from “Children” to “Kids”.

2. In order to Update any leaf associated to category with code “1” the correct parent node xpath and json payload in the request would be as follows:

3. But there can be a user induced error where the payload can contain updated/modified data of grandchild nodes under category with code “1”. And the API would still accept the payload and execute the Update operation.

4. This would result in a partial update of original data as below. Here we can see only the name is updated from Children to Kids. Whereas leaves of grandchild, that is book titled Matilda, remain unchanged, for example price is not updated from 200 to 20

Proposed Solution for Scenario 2

Proposed/Accepted Solution

to be updated. Here we want to update the category `name` from “`Children`” to “`Kids`”.

4. This would result in a partial update of original data as below. Here we can see only the name is updated from Children to Kids. Whereas leaves of grandchild, that is book titled `Matilda,` remain unchanged, for example `price` is not updated from `200` to `20`