Add meteocat exporter

Allows us to track ambient temperature changes and estimate the
temperature delta between the server room and exterior temperature.
We should be able to predict when we would need to stop the machines due
to excesive temperature as summer approaches.

Reviewed-by: Aleix Boné <abonerib@bsc.es>

m/hut/monitoring.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     ../module/slurm-exporter.nix
+    ../module/meteocat-exporter.nix
     ./gpfs-probe.nix
     ./nix-daemon-exporter.nix
   ];
@@ -110,6 +111,7 @@
             "127.0.0.1:9341" # Slurm exporter
             "127.0.0.1:9966" # GPFS custom exporter
             "127.0.0.1:9999" # Nix-daemon custom exporter
+            "127.0.0.1:9929" # Meteocat custom exporter
             "127.0.0.1:${toString config.services.prometheus.exporters.blackbox.port}"
           ];
         }];

m/module/meteocat-exporter.nix

@@ -0,0 +1,17 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  systemd.services."prometheus-meteocat-exporter" = {
+    wantedBy = [ "multi-user.target" ];
+    after = [ "network.target" ];
+    serviceConfig = {
+      Restart = mkDefault "always";
+      PrivateTmp = mkDefault true;
+      WorkingDirectory = mkDefault "/tmp";
+      DynamicUser = mkDefault true;
+      ExecStart = "${pkgs.meteocat-exporter}/bin/meteocat-exporter";
+    };
+  };
+}

pkgs/meteocat-exporter/default.nix

@@ -0,0 +1,25 @@
+{ python3Packages, lib }:
+
+python3Packages.buildPythonApplication rec {
+  pname = "meteocat-exporter";
+  version = "1.0";
+
+  src = ./.;
+
+  doCheck = false;
+
+  build-system = with python3Packages; [
+    setuptools
+  ];
+
+  dependencies = with python3Packages; [
+    beautifulsoup4
+    lxml
+    prometheus-client
+  ];
+
+  meta = with lib; {
+    description = "MeteoCat Prometheus Exporter";
+    platforms = platforms.linux;
+  };
+}

pkgs/meteocat-exporter/meteocat-exporter

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+
+import time
+from prometheus_client import start_http_server, Gauge
+from bs4 import BeautifulSoup
+from urllib import request
+
+# Configuration -------------------------------------------
+meteo_station = "X8" # Barcelona - Zona Universitària
+listening_port = 9929
+update_period = 60 * 5 # Each 5 min
+# ---------------------------------------------------------
+
+metric_tmin = Gauge('meteocat_temp_min', 'Min temperature')
+metric_tmax = Gauge('meteocat_temp_max', 'Max temperature')
+metric_tavg = Gauge('meteocat_temp_avg', 'Average temperature')
+metric_srad = Gauge('meteocat_solar_radiation', 'Solar radiation')
+
+def update(st):
+    url = 'https://www.meteo.cat/observacions/xema/dades?codi=' + st
+    response = request.urlopen(url)
+    data = response.read()
+    soup = BeautifulSoup(data, 'lxml')
+    table = soup.find("table", {"class" : "tblperiode"})
+    rows = table.find_all('tr')
+    row = rows[-1] # Take the last row
+    row_data = []
+    header = row.find('th')
+    header_text = header.text.strip()
+    row_data.append(header_text)
+    for col in row.find_all('td'):
+        row_data.append(col.text)
+    try:
+        # Sometimes it will return '(s/d)' and fail to parse
+        metric_tavg.set(float(row_data[1]))
+        metric_tmax.set(float(row_data[2]))
+        metric_tmin.set(float(row_data[3]))
+        metric_srad.set(float(row_data[10]))
+        #print("ok: temp_avg={}".format(float(row_data[1])))
+    except:
+        print("cannot parse row: {}".format(row))
+        metric_tavg.set(float("nan"))
+        metric_tmax.set(float("nan"))
+        metric_tmin.set(float("nan"))
+        metric_srad.set(float("nan"))
+
+if __name__ == '__main__':
+    start_http_server(port=listening_port, addr="localhost")
+    while True:
+        try:
+            update(meteo_station)
+        except:
+            print("update failed")
+        time.sleep(update_period)

pkgs/meteocat-exporter/setup.py

@@ -0,0 +1,11 @@
+#!/usr/bin/env python
+
+from setuptools import setup, find_packages
+
+setup(name='meteocat-exporter',
+      version='1.0',
+      # Modules to import from other scripts:
+      packages=find_packages(),
+      # Executables
+      scripts=["meteocat-exporter"],
+     )

pkgs/overlay.nix

@@ -54,4 +54,5 @@ final: prev:
   });
 
   prometheus-slurm-exporter = prev.callPackage ./slurm-exporter.nix { };
+  meteocat-exporter = prev.callPackage ./meteocat-exporter/default.nix { };
 }