Add Prometheus metrics for GitHub API calls

cmd/kelos-spawner/main.go

@@ -94,7 +94,7 @@ func main() {
 	log.Info("Starting spawner", "taskspawner", key, "oneShot", oneShot)
 
 	httpClient := &http.Client{
-		Transport: source.NewETagTransport(http.DefaultTransport, log),
+		Transport: source.NewETagTransport(source.NewMetricsTransport(http.DefaultTransport), log),
 	}
 
 	cfgArgs := spawnerRuntimeConfig{

cmd/kelos-spawner/reconciler.go

@@ -91,6 +91,7 @@ func runOnce(ctx context.Context, cl client.Client, key types.NamespacedName, cf
 				Token:     token,
 				TokenFile: cfg.GitHubTokenFile,
 				BaseURL:   cfg.GitHubAPIBaseURL,
+				Client:    cfg.HTTPClient,
 			},
 		}
 		if err := runReportingCycle(ctx, cl, key, reporter); err != nil {

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/onsi/gomega v1.38.3
 	github.com/posthog/posthog-go v1.10.0
 	github.com/prometheus/client_golang v1.23.2
+	github.com/prometheus/client_model v0.6.2
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/spf13/cobra v1.10.2
 	go.uber.org/zap v1.27.0
@@ -72,7 +73,6 @@ require (
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
-	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.66.1 // indirect
 	github.com/prometheus/procfs v0.16.1 // indirect
 	github.com/rogpeppe/go-internal v1.14.1 // indirect

internal/source/metrics_transport.go

@@ -0,0 +1,97 @@
+package source
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var (
+	// githubAPIRequestsTotal counts the total number of GitHub API requests.
+	githubAPIRequestsTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "kelos_github_api_requests_total",
+			Help: "Total number of GitHub API requests",
+		},
+		[]string{"method", "status_code", "resource"},
+	)
+
+	// githubAPIRequestDuration records the duration of GitHub API requests.
+	githubAPIRequestDuration = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Name:    "kelos_github_api_request_duration_seconds",
+			Help:    "Duration of GitHub API requests in seconds",
+			Buckets: prometheus.DefBuckets,
+		},
+		[]string{"method", "resource"},
+	)
+)
+
+func init() {
+	metrics.Registry.MustRegister(
+		githubAPIRequestsTotal,
+		githubAPIRequestDuration,
+	)
+}
+
+type metricsTransport struct {
+	base http.RoundTripper
+}
+
+// NewMetricsTransport wraps a base RoundTripper with Prometheus metrics
+// that track the total number and duration of HTTP requests.
+func NewMetricsTransport(base http.RoundTripper) http.RoundTripper {
+	return &metricsTransport{base: base}
+}
+
+func (t *metricsTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	start := time.Now()
+	resource := classifyResource(req.URL.Path)
+
+	resp, err := t.base.RoundTrip(req)
+
+	duration := time.Since(start).Seconds()
+	githubAPIRequestDuration.WithLabelValues(req.Method, resource).Observe(duration)
+
+	if err != nil {
+		githubAPIRequestsTotal.WithLabelValues(req.Method, "error", resource).Inc()
+		return nil, err
+	}
+
+	githubAPIRequestsTotal.WithLabelValues(req.Method, strconv.Itoa(resp.StatusCode), resource).Inc()
+
+	return resp, nil
+}
+
+// classifyResource extracts the GitHub API resource type from a URL path.
+// It walks backwards through the path segments and returns the first
+// non-numeric segment that matches a known resource type, skipping
+// unknown segments so that sub-resources like "events" do not shadow
+// their parent (e.g. "issues").
+func classifyResource(urlPath string) string {
+	if i := strings.Index(urlPath, "?"); i != -1 {
+		urlPath = urlPath[:i]
+	}
+	segments := strings.Split(strings.Trim(urlPath, "/"), "/")
+	for i := len(segments) - 1; i >= 0; i-- {
+		if _, err := strconv.Atoi(segments[i]); err != nil {
+			switch segments[i] {
+			case "issues":
+				return "issues"
+			case "pulls":
+				return "pulls"
+			case "comments":
+				return "comments"
+			case "reviews":
+				return "reviews"
+			case "collaborators", "permission":
+				return "collaborators"
+			}
+		}
+	}
+	return "other"
+}

internal/source/metrics_transport_test.go

@@ -0,0 +1,164 @@
+package source
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+)
+
+func counterValue(cv *prometheus.CounterVec, labels ...string) float64 {
+	m := &dto.Metric{}
+	if err := cv.WithLabelValues(labels...).Write(m); err != nil {
+		return 0
+	}
+	return m.GetCounter().GetValue()
+}
+
+func histogramCount(hv *prometheus.HistogramVec, labels ...string) uint64 {
+	m := &dto.Metric{}
+	observer, err := hv.GetMetricWithLabelValues(labels...)
+	if err != nil {
+		return 0
+	}
+	if err := observer.(prometheus.Metric).Write(m); err != nil {
+		return 0
+	}
+	return m.GetHistogram().GetSampleCount()
+}
+
+func TestMetricsTransport_CountsRequests(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("ok"))
+	}))
+	defer srv.Close()
+
+	client := &http.Client{Transport: NewMetricsTransport(http.DefaultTransport)}
+
+	before := counterValue(githubAPIRequestsTotal, "GET", "200", "issues")
+
+	resp, err := client.Get(srv.URL + "/repos/owner/repo/issues")
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+
+	after := counterValue(githubAPIRequestsTotal, "GET", "200", "issues")
+	if after-before != 1 {
+		t.Fatalf("Expected counter to increment by 1, got %f", after-before)
+	}
+}
+
+func TestMetricsTransport_CountsErrorStatus(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusForbidden)
+	}))
+	defer srv.Close()
+
+	client := &http.Client{Transport: NewMetricsTransport(http.DefaultTransport)}
+
+	before := counterValue(githubAPIRequestsTotal, "GET", "403", "issues")
+
+	resp, err := client.Get(srv.URL + "/repos/owner/repo/issues")
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+
+	after := counterValue(githubAPIRequestsTotal, "GET", "403", "issues")
+	if after-before != 1 {
+		t.Fatalf("Expected counter to increment by 1 for 403, got %f", after-before)
+	}
+}
+
+func TestMetricsTransport_RecordsDuration(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	client := &http.Client{Transport: NewMetricsTransport(http.DefaultTransport)}
+
+	beforeCount := histogramCount(githubAPIRequestDuration, "GET", "pulls")
+
+	resp, err := client.Get(srv.URL + "/repos/owner/repo/pulls")
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+
+	afterCount := histogramCount(githubAPIRequestDuration, "GET", "pulls")
+	if afterCount-beforeCount != 1 {
+		t.Fatalf("Expected histogram sample count to increment by 1, got %d", afterCount-beforeCount)
+	}
+}
+
+func TestMetricsTransport_CountsTransportErrors(t *testing.T) {
+	client := &http.Client{Transport: NewMetricsTransport(http.DefaultTransport)}
+
+	before := counterValue(githubAPIRequestsTotal, "GET", "error", "other")
+
+	// Request to a closed server to trigger a transport error.
+	_, err := client.Get("http://127.0.0.1:1/unknown")
+	if err == nil {
+		t.Fatal("Expected transport error")
+	}
+
+	after := counterValue(githubAPIRequestsTotal, "GET", "error", "other")
+	if after-before != 1 {
+		t.Fatalf("Expected error counter to increment by 1, got %f", after-before)
+	}
+}
+
+func TestMetricsTransport_TracksPOST(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusCreated)
+	}))
+	defer srv.Close()
+
+	client := &http.Client{Transport: NewMetricsTransport(http.DefaultTransport)}
+
+	before := counterValue(githubAPIRequestsTotal, "POST", "201", "comments")
+
+	resp, err := client.Post(srv.URL+"/repos/owner/repo/issues/1/comments", "application/json", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+
+	after := counterValue(githubAPIRequestsTotal, "POST", "201", "comments")
+	if after-before != 1 {
+		t.Fatalf("Expected POST counter to increment by 1, got %f", after-before)
+	}
+}
+
+func TestClassifyResource(t *testing.T) {
+	tests := []struct {
+		path     string
+		expected string
+	}{
+		{"/repos/owner/repo/issues", "issues"},
+		{"/repos/owner/repo/issues?per_page=100", "issues"},
+		{"/repos/owner/repo/issues/1/comments", "comments"},
+		{"/repos/owner/repo/issues/1/comments?per_page=100", "comments"},
+		{"/repos/owner/repo/pulls", "pulls"},
+		{"/repos/owner/repo/pulls/1/reviews", "reviews"},
+		{"/repos/owner/repo/pulls/1/comments", "comments"},
+		{"/repos/owner/repo/issues/comments/123", "comments"},
+		{"/repos/owner/repo/collaborators/user/permission", "collaborators"},
+		{"/repos/owner/repo/issues/123/events", "issues"},
+		{"/repos/owner/repo/pulls/1/requested_reviewers", "pulls"},
+		{"/unknown/path", "other"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			got := classifyResource(tt.path)
+			if got != tt.expected {
+				t.Errorf("classifyResource(%q) = %q, want %q", tt.path, got, tt.expected)
+			}
+		})
+	}
+}