Many parallel requests on Overpass API

[mmd-osm]

Hi,

I've already opened a similar issue for briefkastenkarte: bierett/briefkastenkarte#8. As stated by someone else, this repo is probably a better place to report it... Please check this issue first for a detailed issue description + recommendations.

Basically, splitting up a (rather small) bbox into many small parts and trying to load them in parallel is not the most efficient approach, given that Overpass API will only handle one request at a time (rambler instance being the exception atm). Even worse, it creates unnecessary overhead without getting the data any faster due to serialization. Creating a large number of requests in a short timeframe also increases chances for HTTP 429 errors.

In additional please also check Rolands comments on this topic: https://lists.openstreetmap.org/pipermail/talk-de/2015-May/111111.html

[k-nut]

This is actually exactly what this (unmerged) Pull Request tries to solve: #28

[mmd-osm]

Thanks for the quick feedback!

Hmm, the PR probably needs a bit of a cleanup before merging, as it changes repo URLs in bower.json, (C) in LICENSE, refers to a "new fork", etc.

What will be the 'official' repo for the future with the new logic in place?

[k-nut]

I guess one could just merge the initial commits that did not refer to a fork yet. Probably depends on when @kartenkarsten finds time (and willingness) to do it.

[kartenkarsten]

In the moment I haven't got enough time for this project. Therefore I think future development should be placed at the fork of @GuillaumeAmat. But I'll do for now a last update with PR #30 .

[GuillaumeAmat]

Oh no... My PR was clean at the beginning and lately I forgot that my additional commits will messed up this PR.

Sorry, my bad... :/

[nrenner]

I made a small debug page (Gist) to visualize request bounding boxes. Use the layer switcher to compare with different options, also see console for request counts.

The specific problem with briefkastenkarte.de seems to be that it uses minzoom: 12 (default: 15), which is two levels lower than the OverPassLayer requestZoomLevel= 14.

Allowing zooms lower than a fixed tiling zoom means that the number of tiles quadruples with each lower level. So at z12 it seems to send hundreds of requests (see second debug layer "minzoom 12")!