Add Docker configs

Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.24-alpine AS builder
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN go mod download
+COPY main.go ./
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o ctlog-uptime-exporter .
+
+FROM scratch
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /build/ctlog-uptime-exporter /ctlog-uptime-exporter
+EXPOSE 9781
+ENTRYPOINT ["/ctlog-uptime-exporter"]

docker-compose.yml

@@ -0,0 +1,12 @@
+services:
+  ctlog-uptime-exporter:
+    build: .
+    image: git.ipng.ch/ipng/ctlog-uptime-exporter:latest
+    restart: unless-stopped
+    ports:
+      - "9781:9781"
+    environment:
+      LISTEN: ":9781"
+      URL: "https://www.gstatic.com/ct/compliance/endpoint_uptime_24h.csv"
+      INTERVAL: "25m"
+      JITTER: "5m"

main.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"math/rand"
 	"net/http"
+	"os"
 	"strconv"
 	"sync"
 	"time"
@@ -114,11 +115,30 @@ func (e *exporter) run(csvURL string, interval, jitter time.Duration) {
 	}
 }
 
+func envOr(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
 func main() {
-	addr := flag.String("listen", ":9781", "address to listen on")
-	csvURL := flag.String("url", "https://www.gstatic.com/ct/compliance/endpoint_uptime_24h.csv", "URL of the uptime CSV")
-	interval := flag.Duration("interval", 25*time.Minute, "how often to fetch the CSV")
-	jitter := flag.Duration("jitter", 5*time.Minute, "maximum +/-jitter applied to the fetch interval")
+	addr := flag.String("listen", envOr("LISTEN", ":9781"), "address to listen on")
+	csvURL := flag.String("url", envOr("URL", "https://www.gstatic.com/ct/compliance/endpoint_uptime_24h.csv"), "URL of the uptime CSV")
+	interval := flag.Duration("interval", func() time.Duration {
+		d, err := time.ParseDuration(envOr("INTERVAL", "25m"))
+		if err != nil {
+			log.Fatalf("invalid INTERVAL: %v", err)
+		}
+		return d
+	}(), "how often to fetch the CSV")
+	jitter := flag.Duration("jitter", func() time.Duration {
+		d, err := time.ParseDuration(envOr("JITTER", "5m"))
+		if err != nil {
+			log.Fatalf("invalid JITTER: %v", err)
+		}
+		return d
+	}(), "maximum +/-jitter applied to the fetch interval")
 	flag.Parse()
 
 	reg := prometheus.NewRegistry()