CRUD service response on unique constraint violation

[malta895]

I need to match in a service the unique constraint violation error when inserting an item to a collection.

I tried to add a document that violates such constraint with a call like the following:

curl --location --request POST 'https://crud-service/some-collection/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "someUniqueField": "some-already-existing"
}'

And I got the following error response:

{
    "statusCode": 422,
    "error": "Unprocessable Entity",
    "message": "E11000 duplicate key error collection: some-collection index: some_unique_index dup key: { someUniqueField: \"some-already-existing\" }"
}

Is it guaranteed that a response with 422 status code is due to a unique constraint violation?
Should I also parse the message in the response looking for the specific mongo error code E11000?

[silversoul93]

Hi @malta895, looking at the source code of the crud-service seems like right now you can get a 422 only for this kind of error during an insert or bulk insert operation.

I don't know if, in the future, other cases could be added.

Since the eventual addition of a new 422 response status code is not a breaking change probably you should parse the message.

According to the MongoDB Documentation, E11000 is the "duplicate key" error, so it should be safe (for now at least).

[malta895]

Hi @silversoul93, thanks for your answer, I think I'll parse the message to be sure.

However in my opinion the CRUD service should take charge of this parsing and return a more appropriate HTTP error status code such as 409 Conflict. On the other hand this is a breaking change, so I'm not sure if it is the right thing to modify the current behavior.

[silversoul93]

@fredmaggiowski @davidebianchi Maybe we can think to add some other metadata field that can be used for such use cases?
e.g.

{
  "statusCode": 422,
  "error": "Unprocessable entity",
  "message": "E11000 ...",
  "metadata": {
    "crudServiceErrorId": "PRIMARY_KEY_INDEX_CONFLICT",
    "crudServiceErrorDescription": "..."
  }
}

This should not be breaking

[fredmaggiowski]

Hey, we could introduce the concept of errorCodes to provide fine graded details about the error (even though I like the 409 status code, we should investigate if it is appropriate).

Let's hear from the crud service maintainers @nicocampagna FYI

[TheRusCompass]

Hello guys! Thank you for all your suggestions!
Yes errorCodes is a very good idea! We were already thinking about it and we can add it to the roadmap.
At the moment I agree with @silversoul93 to parse the message