Revise HTTP status code 400 Bad Request for OSRM service soft-errors (e.g. NoRoute)

[fab-girard]

Hello,
I'm facing a strange behavior with viaroute...
This query:
http://router.project-osrm.org/viaroute?loc=49.1716783,-0.34655726&loc=49.17131276,-0.34673758
returns {"status":400,"status_message":"No route found between points"}
(some other similar requests returns also {"status":400,"status_message":"Bad request"})

I guess it should be:
{"status":207,"status_message":"Impossible route between points"}

Another thing: with http://map.project-osrm.org/ when I tried to route these 2 points, it doesn't work too... but if I move the points on a connected road around, and move again the points on the original position, a route is found! This seems to be caused by hint parameter.

Fab

[perliedman]

A bump on this issue.

I only learned about this feature of the OSRM 5 API from perliedman/leaflet-routing-machine#302. In my opinion, this seems like a less than perfect error to return if no route can be found.

From RFC 7231 section 6.5.1:

400 Bad Request
The 400 (Bad Request) status code indicates that the server cannot or
will not process the request due to something that is perceived to be
a client error (e.g., malformed request syntax, invalid request
message framing, or deceptive request routing).

At least to me, submitting something that is not routable is clearly not a client error - it should be possible for the client to tell from the HTTP status code if it's a malformed request (missing parameters or similar), or just that the coordinates didn't match any existing data on the client.

I would say that 404 is a better code in this case, but I'm not an HTTP/REST expert, so there might be better alternatives.

[daniel-j-h]

Updating to v5 API (link):

http 'http://router.project-osrm.org/route/v1/driving/-0.34655726,49.1716783;-0.34673758,49.17131276'

returns header

HTTP/1.1 400 Bad Request

payload

{
    "code": "NoRoute", 
    "message": "No route found between points"
}

Note that if we want to change this it's breaking the API. I'm tagging this for a potential OSRM 6 release.

[TheMarex]

Looping in @freenerd for opinion on status codes. I think on the Mapbox Directions side we return 402?

[freenerd]

The current state we have adopted on Mapbox Directions is that NoRoute is HTTP 200. Two reasons:

• Internet Explorer 8 and XDomainRequest does not work with well with non-200 HTTP status codes. Given that IE 0.8 usage is under 1% now, I feel good not caring anymore.
• The request the user is doing is actually a valid request. OSRM can handle it, looks up a route and finds that there is zero. It returns zero routes then. My gut feeling is that HTTP 404 is more appropriate though, since we could not find a response object for the given input coordinates. I'm good with doing that switch in OSRM 6.