Internal Server Error when assigning a non-existent DSR

[ocket8888]

I'm submitting a ...

• bug report

Traffic Control components affected ...

• Traffic Ops

Current behavior:

Trying to assign a Delivery Service Request which does not exist to any user will result in an Internal Server error.

Expected / new behavior:

If a resource is not found, the API should communicate that with the 404 Not Found HTTP status code.

Minimal reproduction of the problem with instructions:

Given that no Delivery Service Request exists with the ID 1, attempt to assign Delivery Service Request 1 to any (existing) user. I used my own user (who had the ID 9 in the following example) and it looks like this:

Request

PUT /api/2.0/deliveryservice_requests/1/assign HTTP/1.1
User-Agent: python-requests/2.22.0
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
Cookie: mojolicious=...
Content-Length: 15

{"assigneeId": 9}

(Note also that the documentation specifies a required "id" property of the request body - that is not correct. The DSR to be assigned is fully identified by the request URI.)

Response

HTTP/1.1 500 Internal Server Error
Content-Encoding: gzip
Content-Type: application/json
Set-Cookie: mojolicious=...
Vary: Accept-Encoding
X-Server-Name: traffic_ops_golang/
Date: Tue, 15 Sep 2020 23:34:43 GMT
Content-Length: 83

{
	"alerts": [
		{
			"text": "Internal Server Error",
			"level": "error"
		}
	]
}

Anything else:

From the stack trace I found:

INFO: routing.go:249: 2020-09-15T23:26:42.644209507Z: PUT /api/2.0/deliveryservice_requests/1/assign? handling (reqid 33624)
DEBUG: plugin.go:190: 2020-09-15T23:26:42.644259514Z: DEBUG plugins.OnRequest calling 0 plugins
ERROR: api.go:209: 2020-09-15T23:26:42.651463829Z: 172.20.0.1:47534 dsr assignment querying existing: sql: no rows in result set
DEBUG: api.go:214: 2020-09-15T23:26:42.651514639Z: Internal Server Error
172.20.0.1:47534 - admin [15/Sep/2020:23:26:42 +0000] "PUT /api/2.0/deliveryservice_requests/1/assign? HTTP/1.1" 500 83 7 "python-requests/2.22.0" 2703160290 NON_IMS
INFO: routing.go:252: 2020-09-15T23:26:42.652031369Z: PUT /api/2.0/deliveryservice_requests/1/assign? handled (reqid 33624) in 7.774269ms

which suggests that a database/sql.ErrNoRows isn't being handled somewhere.