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[overpass] Overpass Quotas


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  • From: Roland Olbricht <roland.olbricht@gmx.de>
  • To: overpass@listes.openstreetmap.fr, osm-talk <talk@openstreetmap.org>
  • Subject: [overpass] Overpass Quotas
  • Date: Mon, 27 Apr 2015 22:27:31 +0200

Dear all,

in the last weeks the server overpass-api.de has seen a flood of extra requests. Unfortunately, most of these requests have been from a few clumsy clients.

The standard pattern has been apparently a server that fires as much requests as possible, often some or most of them syntactically correct, but semantically nonsense. For example, from one IP adress was sent the same query for objects with name "Lipkenskothen" every 5 seconds (It is very unlikely that these few results change more often than once per month, hence a frequency of once per day would be more than enough).

While I may block such extreme cases with "iptables" (i.e., the server then appears unreachable from that IP), I would like to avoid manual blocking as much as possible. Beside the quite hard challenge of being unbiased in blocking decisions, it is also a lot of annoying work.

For that purpose I have changed the quota calculation. I will uphold the basic rule that a client shall not send more than one request in parallel from an IP. For the other details, I'm trying an A/B-strategy for traffic management, hence they may change quite often at the moment.

If you encounter a serious service degradation, in particular sustaining HTTP 429 responses, please contact me by mail such that I can adjust the algorithm to make fewer or no false positives.

Cheers,

Roland



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