monitoring: add Waldbrandgefahrenstufen Exporter

hosts/monitoring/configuration.nix

@@ -28,6 +28,18 @@ with lib;
     configFile = ./blackbox.yml;
   };
   services.prometheus.exporters.node.enable = true;
+
+  systemd.services.waldbrandgefahrenstufen-exporter = {
+    description = "Waldbrandgefahrenstufen Exporter";
+    wantedBy = [ "multi-user.target" ];
+
+    serviceConfig = {
+      DynamicUser = "yes";
+    };
+
+    script = "${pkgs.python3}/bin/python ${./waldbrandgefahrenstufen-exporter.py}";
+  };
+
   services.prometheus.alertmanager = {
     enable = true;
     listenAddress = "[::1]";
@@ -227,6 +239,17 @@ with lib;
           }
         ];
       }
+      {
+        job_name = "waldbrandgefahrenstufen";
+        scrape_interval = "1h";
+        static_configs = [
+          {
+            targets = [
+              "[::1]:9242"
+            ];
+          }
+        ];
+      }
     ];
     alertmanagers = [
       {

hosts/monitoring/waldbrandgefahrenstufen-exporter.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+from http.server import HTTPServer, BaseHTTPRequestHandler, HTTPStatus
+import io
+import socket
+import urllib.request
+import xml.etree.ElementTree as ET
+
+class HTTPServerV6(HTTPServer):
+    address_family = socket.AF_INET6
+
+
+class ExporterRequestHandler(BaseHTTPRequestHandler):
+    def do_GET(self):
+        if self.path == "/":
+            self.make_response("Waldbrandgefahrenstufen Exporter für Brandenburg")
+        elif self.path == "/metrics":
+            self.export()
+        else:
+            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
+            return
+
+    def do_HEAD(self):
+        if self.path == "/":
+            self.make_response("Waldbrandgefahrenstufen Exporter für Brandenburg", head_only=True)
+        elif self.path == "/metrics":
+            self.export(head_only=True)
+        else:
+            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
+            return
+
+    def export(self, head_only=False):
+        r = []
+        with urllib.request.urlopen("https://mluk.brandenburg.de/mluk/de/wgs.xml") as f:
+            tree = ET.parse(f)
+            root = tree.getroot()
+            for lk in root[0].findall("landkreis"):
+                r.append('waldbrandgefahrenstufe{{landkreis="{landkreis}"}} {value}'.format(landkreis=lk.attrib["name"], value=lk.text))
+        self.make_response("\n".join(r), head_only=head_only)
+
+    def make_response(self, content, head_only=False):
+        encoded = content.encode("utf-8")
+        self.send_response(HTTPStatus.OK)
+        self.send_header("Content-Type", "text/plain; charset=utf-8")
+        self.send_header("Conten-Length", str(len(encoded)))
+        self.end_headers()
+        if not head_only:
+            self.wfile.write(encoded)
+
+
+def run():
+    with HTTPServerV6(("::1", 9242), ExporterRequestHandler) as httpd:
+        print("Starting Waldbrandgefahrenstufen Exporter on http://[{}]:{}".format(*httpd.socket.getsockname()[:2]))
+        httpd.serve_forever()
+
+if __name__ == "__main__":
+    run()