feat: making things a lot more proper (#11)

.github/dependabot.yml

@@ -0,0 +1,25 @@
+version: 2
+updates:
+  - package-ecosystem: gomod
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    groups:
+      go-deps:
+        patterns:
+          - "*"
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: docker
+    directory: /
+    schedule:
+      interval: weekly

.github/workflows/pr-check.yml

@@ -16,3 +16,8 @@ jobs:
 
       - name: Test
         run: go test -race ./...
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@v6
+        with:
+          version: latest

.github/workflows/release.yml

@@ -66,6 +66,9 @@ jobs:
           context: .
           push: true
           platforms: linux/amd64,linux/arm64
+          build-args: |
+            VERSION=${{ steps.version.outputs.version }}
+            COMMIT=${{ github.sha }}
           tags: |
             rwejlgaard/octopus_exporter:${{ steps.version.outputs.version }}
             rwejlgaard/octopus_exporter:latest

.gitignore

@@ -1,2 +1,5 @@
 .env
 coverage.out
+/octopus_exporter
+*.test
+*.out

.golangci.yml

@@ -0,0 +1,23 @@
+version: "2"
+
+run:
+  timeout: 5m
+
+linters:
+  default: standard
+  enable:
+    - errcheck
+    - govet
+    - ineffassign
+    - staticcheck
+    - unused
+    - misspell
+    - bodyclose
+    - gocritic
+    - unconvert
+    - unparam
+  exclusions:
+    rules:
+      - path: _test\.go
+        linters:
+          - errcheck

Dockerfile

@@ -1,12 +1,17 @@
 FROM golang:1.24-alpine AS builder
+ARG VERSION=dev
+ARG COMMIT=none
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
-RUN CGO_ENABLED=0 go build -o /octopus_exporter ./cmd/octopus_exporter
+RUN CGO_ENABLED=0 go build \
+    -ldflags "-s -w -X main.version=${VERSION} -X main.commit=${COMMIT}" \
+    -o /octopus_exporter ./cmd/octopus_exporter
 
 FROM scratch
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=builder /octopus_exporter /octopus_exporter
+USER 65534:65534
 EXPOSE 9359
 ENTRYPOINT ["/octopus_exporter"]

README.md

@@ -34,7 +34,18 @@ Gas metrics are only exposed if a smart gas meter is found on the account.
 |---|---|---|
 | `octopus_account_balance_pence` | GraphQL | Account balance in pence (positive = credit, negative = debit) |
 
-Metrics are updated every 60 seconds.
+### Exporter health
+
+| Metric | Description |
+|---|---|
+| `octopus_up` | 1 if the last poll cycle completed without errors, 0 otherwise |
+| `octopus_last_poll_timestamp` | Unix timestamp of the last completed poll cycle |
+| `octopus_poll_errors_total` | Total number of collector errors across all poll cycles |
+| `octopus_token_refreshes_total` | Total number of successful JWT token refreshes |
+| `octopus_rate_limit_retries_total` | Total number of 429 rate-limit retries |
+| `octopus_build_info{version,commit}` | Build metadata (always 1) |
+
+Metrics are refreshed every `POLL_INTERVAL` (default 60 seconds).
 
 ## Configuration
 
@@ -48,6 +59,7 @@ Metrics are updated every 60 seconds.
 | `OCTOPUS_GAS_SERIAL` | No | Filter gas meter by serial number |
 | `OCTOPUS_GAS_DEVICE_ID` | No | Use a specific gas smart device ID directly |
 | `PORT` | No | Port to expose metrics on (default: `9359`) |
+| `POLL_INTERVAL` | No | How often to poll Octopus APIs (Go duration, default: `60s`) |
 
 If no filter variables are set, the exporter auto-discovers the first smart meter of each type found on the account. Use `OCTOPUS_MPAN` / `OCTOPUS_MPRN` to pin to a specific meter on accounts with multiple meters.
 
@@ -79,7 +91,7 @@ services:
 
 ## Running from source
 
-Requires Go 1.22+.
+Requires Go 1.24+.
 
 ```sh
 git clone https://github.com/rwejlgaard/octopus_exporter

cmd/octopus_exporter/client.go

@@ -63,7 +63,7 @@ func executeWithRetry(makeReq func() (*http.Request, error)) ([]byte, error) {
 			return nil, err
 		}
 		if resp.StatusCode == http.StatusTooManyRequests {
-			resp.Body.Close()
+			_ = resp.Body.Close()
 			if attempt == maxRetries {
 				return nil, errors.New("rate limited: max retries exceeded")
 			}
@@ -82,7 +82,7 @@ func executeWithRetry(makeReq func() (*http.Request, error)) ([]byte, error) {
 			continue
 		}
 		raw, err := io.ReadAll(resp.Body)
-		resp.Body.Close()
+		_ = resp.Body.Close()
 		if err != nil {
 			return nil, err
 		}

cmd/octopus_exporter/main.go

@@ -1,12 +1,15 @@
 package main
 
 import (
+	"context"
 	"errors"
 	"log"
 	"net/http"
 	"os"
+	"os/signal"
 	"sync"
 	"sync/atomic"
+	"syscall"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -14,8 +17,10 @@ import (
 )
 
 var (
-	apiKey string
+	apiKey  string
-	port   string
+	port    string
+	version = "dev"
+	commit  = "none"
 )
 
 func mustEnv(key string) string {
@@ -41,9 +46,24 @@ func counter(name, help string) prometheus.Counter {
 	return prometheus.NewCounter(prometheus.CounterOpts{Name: name, Help: help})
 }
 
+func parseInterval(key string, def time.Duration) time.Duration {
+	v := os.Getenv(key)
+	if v == "" {
+		return def
+	}
+	d, err := time.ParseDuration(v)
+	if err != nil {
+		log.Printf("invalid %s=%q, falling back to %s: %v", key, v, def, err)
+		return def
+	}
+	return d
+}
+
 func main() {
 	apiKey = mustEnv("OCTOPUS_API_KEY")
 	port = envOrDefault("PORT", "9359")
+	pollInterval := parseInterval("POLL_INTERVAL", 60*time.Second)
+	log.Printf("octopus_exporter %s (%s), poll interval %s", version, commit, pollInterval)
 
 	token, err := getKrakenToken(apiKey)
 	if err != nil {
@@ -91,16 +111,24 @@ func main() {
 
 	// Exporter health
 	exporterUp := gauge("octopus_up", "1 if the last poll cycle completed without errors, 0 otherwise")
+	lastPollTimestamp := gauge("octopus_last_poll_timestamp", "Unix timestamp of the last completed poll cycle")
 	pollErrors := counter("octopus_poll_errors_total", "Total number of collector errors per poll cycle")
 	tokenRefreshCount := counter("octopus_token_refreshes_total", "Total number of successful JWT token refreshes")
 	rateLimitRetries = counter("octopus_rate_limit_retries_total", "Total number of 429 rate-limit retries across all requests")
 
+	buildInfo := prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Name: "octopus_build_info",
+		Help: "Build metadata exposed as a constant gauge (always 1).",
+	}, []string{"version", "commit"})
+	buildInfo.WithLabelValues(version, commit).Set(1)
+
 	toRegister := []prometheus.Collector{
 		elecDemand, elecLastRead,
 		elecConsumption, elecConsumptionInterval,
 		elecUnitRate, elecStandingCharge,
 		accountBalance,
-		exporterUp, pollErrors, tokenRefreshCount, rateLimitRetries,
+		exporterUp, lastPollTimestamp, pollErrors, tokenRefreshCount, rateLimitRetries,
+		buildInfo,
 	}
 
 	var (
@@ -123,10 +151,23 @@ func main() {
 
 	prometheus.MustRegister(toRegister...)
 
-	http.Handle("/metrics", promhttp.Handler())
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+	srv := &http.Server{
+		Addr:              ":" + port,
+		Handler:           mux,
+		ReadHeaderTimeout: 5 * time.Second,
+	}
 	go func() {
 		log.Printf("serving metrics on :%s/metrics", port)
-		if err := http.ListenAndServe(":"+port, nil); err != nil {
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
 			log.Fatal(err)
 		}
 	}()
@@ -163,7 +204,10 @@ func main() {
 		return fn(newT)
 	}
 
-	for {
+	ticker := time.NewTicker(pollInterval)
+	defer ticker.Stop()
+
+	poll := func() {
 		var (
 			wg        sync.WaitGroup
 			failedAny atomic.Bool
@@ -296,7 +340,22 @@ func main() {
 		} else {
 			exporterUp.Set(1)
 		}
+		lastPollTimestamp.Set(float64(time.Now().Unix()))
+	}
 
-		time.Sleep(60 * time.Second)
+	poll()
+	for {
+		select {
+		case <-ctx.Done():
+			log.Println("shutdown signal received, draining HTTP server")
+			shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+			defer cancel()
+			if err := srv.Shutdown(shutdownCtx); err != nil {
+				log.Printf("HTTP shutdown error: %v", err)
+			}
+			return
+		case <-ticker.C:
+			poll()
+		}
 	}
 }

go.mod

@@ -1,6 +1,6 @@
 module github.com/pez/octopus_exporter
 
-go 1.22
+go 1.24
 
 require github.com/prometheus/client_golang v1.19.1