How to reduce requests to OSRM servers

[lonvia]

As with any other free service out there on the internet, the Fossgis OSRM servers have been struggling with overuse. As a consequence, we started to introduce rate limiting on the servers. Sadly, this interferes with the rather cool route-as-you-drag feature on the website. If you drag around a route, you end up pretty quickly with a 429 from the servers.

I wanted to open a discussion here what we should do about that. Some possible solutions I see:

• Disable route-as-you-drag. This would be the easiest and Valhalla and Graphhopper can't do it either. Still, would be somewhat sad to see the feature go.
• Reduce number of requests during dragging. If you can reduce it to something like 3/s then we can work with a burst on the OSRM server side that allows continued dragging for at least 15s. That should be more than sufficient.
• Proxy via the webservers. If the requests come from fixed IPs, we can exclude those. That would make things more sluggish though. And possibly overly complicated.

What do you think? Other ideas?

CC @datendelphin

[1ec5]

Would it be feasible to mark requests that are intended for the route-to-drag feature and give them a more generous rate limit? This call swallows the distinction between drag-initiated and non-drag-initiated requests:

openstreetmap-website/app/assets/javascripts/index/directions.js

Line 20 in c32ac98

getRoute(false, !dragging);

openstreetmap-website/app/assets/javascripts/index/directions.js

Line 95 in c32ac98

function getRoute(fitRoute = true, reportErrors = true) {

[lonvia]

We could actually defer that from the hints parameter. I'm not convinced it is better than checking for an openstreetmap.org referrer though.

Maybe we can slow down requests with the hints parameter a bit. That would have the advantage of "fixing" rate-limiting for all route-as-you-drag implementations that behave properly (i.e. sending requests sequentially).