refactor: enhance Overpass API handling with multiple endpoints and improved error reporting

lib/maptool/overpass_pois.rb

@@ -12,7 +12,15 @@ module Maptool
   module OverpassPois
     class FetchError < StandardError; end
 
-    OVERPASS_API = "https://overpass-api.de/api/interpreter".freeze
+    # Same three public mirrors public/js/hiking_trails.js races — tried in
+    # turn here instead, falling through to the next on any failure: the
+    # shared free instances regularly 504/429 under load, and a plugin run
+    # is a one-off click, not worth threads to race them.
+    OVERPASS_APIS = [
+      "https://overpass-api.de/api/interpreter",
+      "https://overpass.kumi.systems/api/interpreter",
+      "https://overpass.private.coffee/api/interpreter",
+    ].freeze
 
     # Each entry: an Overpass tag filter -> { label:, icon:, color: }, used
     # both to build the query (unioning every filter) and to label/style
@@ -53,12 +61,23 @@ module Maptool
     # bbox: [south, west, north, east] (Overpass's own axis order).
     def self.fetch(bbox, timeout: 60)
       query = build_query(bbox, timeout: timeout)
-      uri = URI(OVERPASS_API)
+      errors = OVERPASS_APIS.map do |url|
+        return post(URI(url), query, timeout)
+      rescue FetchError, Net::OpenTimeout, Net::ReadTimeout, SystemCallError, SocketError, OpenSSL::SSL::SSLError, JSON::ParserError => e
+        "#{URI(url).host}: #{e.message}"
+      end
+      raise FetchError, errors.join("; ")
+    end
+
+    def self.post(uri, query, timeout)
       # overpass-api.de answers Net::HTTP's default "Ruby" User-Agent with
       # a 406 (verified 2026-10-09) — any identifying UA gets through.
       request = Net::HTTP::Post.new(uri, "User-Agent" => "maptool (Overpass camper POIs plugin)")
       request.set_form_data("data" => query)
-      response = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |http| http.request(request) }
+      # read_timeout past the query's own [timeout:] — Net::HTTP's default
+      # 60s equals it, so a big viewport could hit Net::ReadTimeout just as
+      # Overpass was about to answer (a country-sized bbox measured ~57s).
+      response = Net::HTTP.start(uri.host, uri.port, use_ssl: true, read_timeout: timeout + 30) { |http| http.request(request) }
       raise FetchError, "unexpected response #{response.code}" unless response.is_a?(Net::HTTPSuccess)
 
       JSON.parse(response.body)

lib/maptool/plugins.rb

@@ -65,8 +65,13 @@ module Maptool
       south, west, north, east = bbox
       args = ["--south=#{south}", "--west=#{west}", "--north=#{north}", "--east=#{east}"]
 
-      stdout, _stderr, status = Open3.capture3(command, *args, chdir: plugin_dir)
-      raise RunError, "plugin exited with status #{status.exitstatus}" unless status.success?
+      stdout, stderr, status = Open3.capture3(command, *args, chdir: plugin_dir)
+      # First stderr line too — for a Ruby plugin that's the exception
+      # message (e.g. "...: unexpected response 406"), the only clue to why.
+      unless status.success?
+        reason = stderr.lines.first&.strip
+        raise RunError, ["plugin exited with status #{status.exitstatus}", reason].compact.reject(&:empty?).join(": ")
+      end
 
       geojson = JSON.parse(stdout)
       raise RunError, "plugin did not print a GeoJSON FeatureCollection" unless geojson.is_a?(Hash) && geojson["type"] == "FeatureCollection"