rewrite weather in go

flake.nix

@@ -94,6 +94,7 @@
           deploy-rs-pkg = null;
         })
         (_: super: {
+          weather = super.callPackage ./pkgs/weather { };
           nicer = super.callPackage ./pkgs/nicer.nix { };
           imapsync = super.callPackage ./pkgs/imapsync.nix { };
           tmuxbash = super.callPackage ./pkgs/tmuxbash.nix { };
@@ -305,19 +306,20 @@
         };
 
         formatter = pkgs.nixfmt-rfc-style;
-
       }
     )
 
-    // {
+    // (
-      packages.x86_64-linux.vanta-agent =
       let
         pkgs = import nixpkgs {
           inherit overlays;
           system = "x86_64-linux";
         };
       in
-        pkgs.vanta-agent;
+      {
-    };
+        packages.x86_64-linux.vanta-agent = pkgs.vanta-agent;
+        packages.x86_64-linux.weather = pkgs.weather;
+      }
+    );
 
 }

hosts/fwminex/configuration.nix

@@ -95,8 +95,8 @@ in
           bash
         ];
         serviceConfig = {
-          type = "notify";
+          type = "simple";
-          ExecStart = "${pkgs.systemd}/bin/systemd-socket-activate -a --inetd -l ${toString myData.ports.exporters.weather} ${../../pkgs/weather/main}";
+          ExecStart = "${pkgs.weather}/bin/weather";
           ProtectSystem = "strict";
         };
       };

pkgs/weather/default.nix

@@ -0,0 +1,6 @@
+{ buildGoModule }:
+buildGoModule {
+  name = "weather";
+  src = ./.;
+  vendorHash = null;
+}

pkgs/weather/go.mod

@@ -0,0 +1,3 @@
+module git.jakstys.lt/motiejus/config/pkgs/weather
+
+go 1.19

pkgs/weather/main

@@ -1,43 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-STATION=vilniaus-ams
-TODAY=${1:-$(date +%F)}
-
-export TZ=UTC
-sed -e 's/$/\r/' <<EOF
-HTTP/1.0 200 OK
-Content-Type: text/plain; version=0.0.4; charset=utf-8; escaping=values
-
-EOF
-
-get() { jq -r ".$1 // 0" <<< "$2"; }
-
-while IFS= read -r obs; do
-    #{
-    #  "observationTimeUtc": "2024-09-13 12:00:00",
-    #  "airTemperature": 20.9,
-    #  "feelsLikeTemperature": 20.9,
-    #  "windSpeed": 1.4,
-    #  "windGust": 5.7,
-    #  "windDirection": 103,
-    #  "cloudCover": 88,
-    #  "seaLevelPressure": 1010.3,
-    #  "relativeHumidity": 82,
-    #  "precipitation": 0,
-    #  "conditionCode": "rain"
-    #}
-    ts=$(date +%s000 --date="$(get observationTimeUtc "$obs")")
-    cat <<EOF
-weather_station_air_temperature_celsius{station="$STATION"} $(get airTemperature "$obs") $ts
-weather_station_air_feels_like_celsius{station="$STATION"} $(get feelsLikeTemperature "$obs") $ts
-weather_station_wind_speed_ms{station="$STATION"} $(get windSpeed "$obs") $ts
-weather_station_wind_gust_ms{station="$STATION"} $(get windGust "$obs") $ts
-weather_station_wind_direction_degrees{station="$STATION"} $(get windDirection "$obs") $ts
-weather_station_cloud_cover_percent{station="$STATION"} $(get cloudCover "$obs") $ts
-weather_station_sea_level_pressure_hpa{station="$STATION"} $(get seaLevelPressure "$obs") $ts
-weather_station_relative_humidity_percent{station="$STATION"} $(get relativeHumidity "$obs") $ts
-weather_station_precipitation_mm{station="$STATION"} $(get precipitation "$obs") $ts
-weather_station_condition{station="$STATION",code="$(get conditionCode "$obs")"} 1 $ts
-EOF
-done < <(curl -f -s "https://api.meteo.lt/v1/stations/$STATION/observations/$TODAY" | jq -c '.observations[]')

pkgs/weather/main.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"text/template"
+	"time"
+)
+
+const (
+	_listen       = ":9011"
+	_urlTemplate  = "https://api.meteo.lt/v1/stations/%s/observations/%s"
+	_station      = "vilniaus-ams"
+	_promTemplate = `weather_station_air_temperature_celsius{station="{{ .Station }}"} {{ .AirTemperature }} {{ .TS }}
+weather_station_air_feels_like_celsius{station="{{ .Station }}"} {{ .FeelsLikeTemperature }} {{ .TS }}
+weather_station_wind_speed_ms{station="{{ .Station }}"} {{ .WindSpeed }} {{ .TS }}
+weather_station_wind_gust_ms{station="{{ .Station }}"} {{ .WindGust }} {{ .TS }}
+weather_station_wind_direction_degrees{station="{{ .Station }}"} {{ .WindDirection }} {{ .TS }}{{ if .CloudCover }}
+weather_station_cloud_cover_percent{station="{{ .Station }}"} {{ .CloudCover }} {{ .TS }}{{ end }}
+weather_station_sea_level_pressure_hpa{station="{{ .Station }}"} {{ .SeaLevelPressure }} {{ .TS }}
+weather_station_relative_humidity_percent{station="{{ .Station }}"} {{ .RelativeHumidity }} {{ .TS }}
+weather_station_precipitation_mm{station="{{ .Station }}"} {{ .Precipitation }} {{ .TS }}{{ if .ConditionCode }}
+weather_station_condition{station="{{ .Station }}",code="{{ .ConditionCode }}"} 1 {{ .TS }}{{ end }}
+`
+)
+
+var tpl = template.Must(template.New("prom").Parse(_promTemplate))
+
+func main() {
+	log.Printf("Listening on %s\n", _listen)
+	log.Fatal((&http.Server{
+		Addr:    _listen,
+		Handler: http.HandlerFunc(handler),
+	}).ListenAndServe())
+}
+
+type observation struct {
+	ObservationTimeUtc   string   `json:"observationTimeUtc"`
+	AirTemperature       float64  `json:"airTemperature"`
+	FeelsLikeTemperature float64  `json:"feelsLikeTemperature"`
+	WindSpeed            float64  `json:"windSpeed"`
+	WindGust             float64  `json:"windGust"`
+	WindDirection        float64  `json:"windDirection"`
+	CloudCover           *float64 `json:"cloudCover"`
+	SeaLevelPressure     float64  `json:"seaLevelPressure"`
+	RelativeHumidity     float64  `json:"relativeHumidity"`
+	Precipitation        float64  `json:"precipitation"`
+	ConditionCode        *string  `json:"conditionCode"`
+
+	// template variables
+	TS      int64
+	Station string
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	observations, err := getObservations(time.Now().UTC(), _station)
+	if err != nil {
+		log.Printf("Error getting observations: %v\n", err)
+		http.Error(w, fmt.Sprintf("Internal error: %v", err.Error()), 500)
+		return
+	}
+	w.Header().Add("Content-Type", "text/plain; version=0.0.4")
+
+	bw := bufio.NewWriter(w)
+	defer bw.Flush()
+
+	for _, observation := range observations {
+
+		ts, err := time.ParseInLocation(
+			time.DateTime,
+			observation.ObservationTimeUtc,
+			time.UTC,
+		)
+		if err != nil {
+			log.Printf("error parsing time %q: %v\n", observation.ObservationTimeUtc, err)
+			return
+		}
+		observation.TS = ts.UnixMilli()
+		observation.Station = _station
+
+		if err := tpl.Execute(bw, observation); err != nil {
+			log.Printf("error executing template: %v", err)
+			return
+		}
+	}
+	bw.WriteString("\n")
+}
+
+func getObservations(date time.Time, station string) ([]observation, error) {
+	url := fmt.Sprintf(_urlTemplate, station, date.Format(time.DateOnly))
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, fmt.Errorf("get %q: %w", url, err)
+	}
+
+	defer func() {
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+	}()
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("got non-200 http status code %d", resp.StatusCode)
+	}
+
+	decoder := json.NewDecoder(resp.Body)
+	var incoming struct {
+		Observations []observation `json:"observations"`
+	}
+	if err := decoder.Decode(&incoming); err != nil {
+		return nil, fmt.Errorf("json decode: %w", err)
+	}
+
+	return incoming.Observations, nil
+}