Agency error and bulk responses

[thekaveman]

This is related to #852 but different enough that I wanted to open a new issue.

Agency references the general Error Messages and Bulk Responses - these describe JSON structures for what succeeded and what failed for a given request. I think this originated in #796 around this commit: https://github.com/openmobilityfoundation/mobility-data-specification/commit/1f4d197d1a6a8d9252d58aae79fa682f8e4a187c

It seems clear that a successful registration/update in an Agency endpoint should return a Bulk Response. #852 is asking which code to use between 200 vs 201.

I'm not as clear on which codes and in what situations either a singular JSON Error Message or a larger JSON Bulk Response (with failures) should be returned?

500

The Responses table for 500 says:

In this case, the answer may contain a text/plain body with an error message for troubleshooting.

It seems like the (JSON) Error Message or Bulk Response should not be used here, since the content type is text/plain. Is that correct?

Or should the language around 500 be updated to allow JSON? Would it return Error Message for GET and Bulk Response for POST/PUT?

409

The Responses table for 409 says:

POST operations when an object already exists and an update is not possible.

This seems like a case for using a Bulk Response - but only for POST? MDN says 409 is more common with PUT.

I also see from the linked commit/PR above that 409 was previously the code associated with these error responses in the Agency docs.

406, 404, and 401

These codes don't really make sense to use with Error Messages or Bulk Responses, no body content is returned with these.

400

Maybe? But then 400 is not referenced in any of the Agency docs, only in the General Info Responses table.

[schnuerle]

Hi @marie-x and @avatarneil do you have some thoughts on this you can share today?

[marie-x]

I'll schedule time with @avatarneil to discuss this morning (Tue 2 May)

[thekaveman]

Here's what I came up with for errors needing Bulk Responses, I'm implementing in the OpenAPI as a starting point but we can always adjust if needed:

Sorted by endpoint

Endpoint	HTTP method	Error key	Error description	HTTP code
/event	POST	bad_param	A validation error occurred	400
/event	POST	missing_param	A required parameter is missing	400
/event	POST	unregistered	This device_id is unregistered	404
/reports	POST	bad_param	A validation error occurred	400
/stops	POST	already_registered	A stop with stop_id is already registered	409
/stops	POST	bad_param	A validation error occurred	400
/stops	POST	missing_param	A required parameter is missing	400
/stops	PUT	bad_param	A validation error occurred	400
/stops	PUT	missing_param	A required parameter is missing	400
/stops	PUT	unregistered	This stop_id is unregistered	404
/telemetry	POST	bad_param	A validation error occurred	400
/telemetry	POST	missing_param	A required parameter is missing	400
/telemetry	POST	unregistered	This device_id is unregistered	404
/trips	POST	bad_param	A validation error occurred	400
/trips	POST	missing_param	A required parameter is missing	400
/trips	POST	unregistered	This device_id is unregistered	404
/vehicles	POST	already_registered	A vehicle with device_id is already registered	409
/vehicles	POST	bad_param	A validation error occurred	400
/vehicles	POST	missing_param	A required parameter is missing	400
/vehicles	PUT	bad_param	A validation error occurred	400
/vehicles	PUT	unregistered	This device_id is unregistered	404

Sorted by Error key

Endpoint	HTTP method	Error key	Error description	HTTP code
/stops	POST	already_registered	A stop with stop_id is already registered	409
/vehicles	POST	already_registered	A vehicle with device_id is already registered	409
/event	POST	bad_param	A validation error occurred	400
/reports	POST	bad_param	A validation error occurred	400
/stops	POST	bad_param	A validation error occurred	400
/stops	PUT	bad_param	A validation error occurred	400
/telemetry	POST	bad_param	A validation error occurred	400
/trips	POST	bad_param	A validation error occurred	400
/vehicles	POST	bad_param	A validation error occurred	400
/vehicles	PUT	bad_param	A validation error occurred	400
/event	POST	missing_param	A required parameter is missing	400
/stops	POST	missing_param	A required parameter is missing	400
/stops	PUT	missing_param	A required parameter is missing	400
/telemetry	POST	missing_param	A required parameter is missing	400
/trips	POST	missing_param	A required parameter is missing	400
/vehicles	POST	missing_param	A required parameter is missing	400
/event	POST	unregistered	This device_id is unregistered	404
/stops	PUT	unregistered	This stop_id is unregistered	404
/telemetry	POST	unregistered	This device_id is unregistered	404
/trips	POST	unregistered	This device_id is unregistered	404
/vehicles	PUT	unregistered	This device_id is unregistered	404

[thekaveman]

I think the final question on this is for 500 -- should that really be a text/plain response, or should that be application/json with the body of the single-error response?

{
  "error": "...",
  "error_description": "...",
  "error_details": ["...", "..."]
}

[schnuerle]

I've made a pass across all APIs to align each endpoint to the responses listed in this comment and in the current OpenAPI and Stoplight docs.

Take a look at the release branch to confirm. Example of how I documented it - see the 'Responses' header.

I did not address the 500 question yet. I could go either way on this so welcome feedback @thekaveman @marie-x @avatarneil If it's a quick easy change to OpenAPI (and we think it's a good idea) let's do it today. For MDS spec it's easy now and just changing one line here.

[marie-x]

application/json I'd say

[thekaveman]

It sounds like would want to update the 500 response across all OpenAPI docs then. I'll work on this this morning and get back to this thread.

[thekaveman]

Fixed the 500 response type/schema across all OpenAPI endpoints in https://github.com/openmobilityfoundation/mds-openapi/pull/37

[thekaveman]

I think this issue can be closed after the one-line update in the spec around 500 response type.

[marie-x]

Nice! Thanks!

[schnuerle]

Alright updated the language here: https://github.com/openmobilityfoundation/mobility-data-specification/pull/837/commits/00189922689039e0fe828734a26ca2dc60982634 (and then fixed "a" to "an").