Issues/Decisions
Introduction
There are few inconsistencies and missing features found within the CPS core APIs. This proposal aims to discuss these problems and suggest appropriate solutions for the same. The following list of APIs are found to be impacted by the findings:
Detailed Analysis
Get a Node
Problem Description:
When a list is fetched using Get a node API then instead of returning a list containing n-number of list nodes, the API returns n-lists containing one data node in each list.
For example: if there is a list named "Items" containing 10 items named Item 1, Item 2, ......, Item 10. Then when fetching this list using get a node API a total of 10 individual lists are returned where each list contains one Item, i.e. List 1→Item 1, List 2→ Item 2, ......., List 10→ Item 10.
Click here to expand...
Data Originally Stored
{
"book-store:bookstore": {
"bookstore-name": "Easons",
"categories": [
{
"code": "1",
"name": "Children",
"books": [
{
"title": "Matilda",
"lang": "English",
"price": 20
},
{
"title": "The Gruffalo",
"lang": "English",
"price": 15
}
]
}
]
}
}
| Response when querying the list directly
[
{
"books": {
"title": "Matilda",
"lang": "English",
"price": 20
}
},
{
"books": {
"title": "The Gruffalo",
"lang": "English",
"price": 15
}
}
]
| Expected Result
[
{
"books": [
{
"title": "Matilda",
"lang": "English",
"price": 20
},
{
"title": "The Gruffalo",
"lang": "English",
"price": 15
}
]
}
]
| This behavior extends to list items stored under root node as well. So, this case needs to be taken into consideration as well |
Initial setup to try the sample requests up ahead
To tryout the sample curl requests below please create a simple bookstore entry in your local CPS deployment. Or just execute the following curl request
curl --location 'http://localhost:8883/cps/api/v2/dataspaces/my-dataspace/anchors/bookstore-example/nodes?xpath=%2F' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: ••••••' --data '{ "bookstore": { "bookstore-name": "Easons", "premises": { "addresses": [ { "house-number": 2, "street": "Main Street", "town": "Maynooth", "county": "Kildare" } ] }, "categories": [ { "code": 1, "name": "Children", "books" : [ { "title": "Matilda", "lang": "English", "authors": ["Roald Dahl"], "editions": [1988, 2000], "price": 20 }, { "title": "The Gruffalo", "lang": "English", "authors": ["Julia Donaldson"], "editions": [1999], "price": 15 } ] }, { "code": 2, "name": "Thriller", "books" : [ { "title": "Annihilation", "lang": "English", "authors": ["Jeff VanderMeer"], "editions": [2014], "price": 15 } ] } ] } } '
Update node leaves
Problem Description
When updating any data node, it's parent node xpath is provided as part of the update request. And the JSON payload contains the data of child node to be updated.
But if the JSON data of the parent node is provided as part of this payload, then instead of failing, the request is successfully executed with partial update Where only the child data node is updated and the parent data node is not updated.
Click here to expand...
Original JSON data: | JSON with updates | JSON data after update | Notes |
|---|
{
"code": 1,
"name": "Children",
"books": [
{
"title": "Matilda",
"lang": "English",
"authors": ["Roald Dahl"],
"editions": [1988, 2000],
"price": 20
}
]
}
|
{
"code": 1,
"name": "Kids",
"books": [
{
"title": "Matilda",
"editions":
[1988, 2000, 2024],
"price": 25
}
]
}
|
{
"code": "1",
"name": "Children",
"books": [
{
"title": "Matilda",
"lang": "English",
"authors": ["Roald Dahl"],
"editions":
[1988, 2000, 2024],
"price": 25
}
]
}
| It can be seen that the leaf data belonging to parent node i.e. code=1 is sent as part of JSON body. Where name is changed from Children to Kids And the fields editions and price, of child node, i.e. title=Matilda are modified. But after the request is executed only the child node is updated. The expected behavior should be to throw an exception as the Update a node API requires parent node xpath to update any child data. Which in this case should be "/bookstore" because the request is also updating the node with key "code=1" This situation can mainly occur due to user error, where user provides updated parent data along with parent node xpath as part of the request.
|
Curl request to replicate the scenario
curl --location --globoff --request PATCH 'http://localhost:8883/cps/api/v2/dataspaces/my-dataspace/anchors/bookstore/nodes?xpath=%2Fbookstore%2Fcategories[%40code%3D1]' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: ••••••' --data '{
"code": 1,
"name": "Kids",
"books": [
{
"title": "Matilda",
"editions":
[1988, 2000, 2024],
"price": 25
}
]
}'
|
Problem Description 2
Update operation can only be done on one node at a time and when trying to update parent child in one request, then only the parent node is updated.
Click here to expand...
Original JSON data | JSON to be updated | Updated JSON data | Notes |
|---|
{
"categories": {
"code": "1",
"name": "Children",
"books": [
{
"title": "Matilda",
"lang": "English",
"price": 200,
"authors":["Roald Dahl"],
"editions": [1988,2000]
}
]
}
}
|
{
"categories": {
"code": 1,
"name": "Kids",
"books": [
{
"title": "Matilda",
"price": 20,
"editions":
[1988, 2000, 2022]
}
]
}
}
|
{
"categories": {
"code": "1",
"name": "Kids",
"books": [
{
"title": "Matilda",
"lang": "English",
"price": 200,
"authors": ["Roald Dahl"],
"editions": [1988,2000] }
]
}
}
| The request is executed successfully but only a partial update takes place in the database. So, either the API should reject any request containing multiple nodes or support updating multiple nodes at once.
|
Curl request to replicate the scenario
curl --location --request PATCH 'http://localhost:8883/cps/api/v2/dataspaces/my-dataspace/anchors/bookstore/nodes?xpath=%2Fbookstore' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: ••••••' --data '{
"categories": {
"code": 1,
"name": "Kids",
"books": [
{
"title": "Matilda",
"price": 20,
"editions":
[1988, 2000, 2022]
}
]
}
}'
|
Replace a node with descendants
Problem Description
If a replace operation is performed on a list, where a new list item is also added to the list, then it results in a 200-response code, with a partial replace operation.
Click here to expand...
Original JSON data | Data to replace | Result after Replace operation | Notes |
|---|
[
{
"book-store:books": {
"title": "Matilda",
"lang": "English",
"price": 20,
"authors": ["Roald Dahl"],
"editions": [1988,2000]
}
}
]
|
{
"books": [
{
"title": "Matilda",
"lang": "English",
"authors": ["Roald Dahl"],
"editions": [2024]
},
{
"title": "The Gruffalo",
"lang": "English",
"authors": ["Julia Donaldson"],
"editions": [1999],
"price": 15
}
]
}
|
[
{
"book-store:books": {
"title": "Matilda",
"lang": "English",
"authors": ["Roald Dahl"],
"editions": [2024]
}
}
]
| This is a user error as request here is itself wrong, because it tries to add a new list element. CPS provides a separate endpoint to Add a list element So, such a scenario should be handled by the API instead of returning a successful response.
|
Curel request to replicate the scenario
curl --location --globoff --request PUT 'http://localhost:8883/cps/api/v2/dataspaces/my-dataspace/anchors/bookstore/nodes?xpath=%2Fbookstore%2Fcategories[%40code%3D1]' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: ••••••' --data '{
"books": [
{
"title": "Matilda",
"lang": "English",
"authors": ["Roald Dahl"],
"editions": [2024]
},
{
"title": "The Gruffalo",
"lang": "English",
"authors": ["Julia Donaldson"],
"editions": [1999],
"price": 15
}
]
}'
|