Codevault initial commit

internal/observability/metrics/configure.go

@@ -0,0 +1,83 @@
+package metrics
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/prometheus"
+	otelmetric "go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
+
+	"github.com/kanootoko/codevault/internal"
+	"github.com/kanootoko/codevault/internal/config"
+	"github.com/kanootoko/codevault/internal/observability"
+	"github.com/kanootoko/codevault/internal/utils/gshutdown"
+)
+
+// Configure starts a Prometheus server which serves metrics and finishes on context finish
+func Configure(ctx context.Context, cfg config.MetricsConfig) error {
+	if cfg.Host == "" {
+		return nil
+	}
+	res, err := observability.GetOtelResource()
+	if err != nil {
+		return fmt.Errorf("cannot get OpenTelemetry resource: %w", err)
+	}
+
+	meterProvider, err := newMeterProvider(res)
+	if err != nil {
+		return fmt.Errorf("cannot instanciate OpenTelemetry meter provider: %w", err)
+	}
+
+	otel.SetMeterProvider(meterProvider)
+
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.Handler())
+	server := http.Server{
+		Addr:              fmt.Sprintf(":%d", cfg.Port),
+		Handler:           mux,
+		ReadTimeout:       time.Second * 20,
+		ReadHeaderTimeout: time.Second * 10,
+		WriteTimeout:      time.Second * 20,
+	}
+	listener, err := net.Listen("tcp", fmt.Sprintf("%s:%d", cfg.Host, cfg.Port))
+	if err != nil {
+		return fmt.Errorf("error on creating listener for prometheus metrics: %w", err)
+	}
+	go func() { _ = server.Serve(listener) }()
+	_ = gshutdown.SubtaskStarted(ctx, "prometheus")
+	go func() {
+		defer func() {
+			_ = listener.Close()
+			_ = gshutdown.SubtaskFinished(ctx, "prometheus")
+		}()
+		<-ctx.Done()
+		_ = server.Shutdown(context.Background())
+	}()
+
+	return nil
+}
+
+func GetMeter() otelmetric.Meter {
+	mp := otel.GetMeterProvider()
+	return mp.Meter(internal.PackageName, otelmetric.WithInstrumentationVersion(internal.Version))
+}
+
+func newMeterProvider(res *resource.Resource) (*metric.MeterProvider, error) {
+	metricExporter, err := prometheus.New()
+	if err != nil {
+		return nil, err
+	}
+
+	meterProvider := metric.NewMeterProvider(
+		metric.WithResource(res),
+		metric.WithReader(metricExporter),
+	)
+	return meterProvider, nil
+}

internal/observability/metrics/metrics.go

@@ -0,0 +1,110 @@
+package metrics
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+
+	"github.com/kanootoko/codevault/internal"
+)
+
+type Metrics struct {
+	HTTP  HTTPMetrics
+	Value ValueMetrics
+}
+
+func NewMetrics(meter metric.Meter) Metrics {
+	metrics := Metrics{
+		HTTP:  newHTTPMetrics(meter),
+		Value: newValueMetrics(meter),
+	}
+	addObservableMetrics(meter)
+	return metrics
+}
+
+type HTTPMetrics struct {
+	// Total HTTP requests with [route, status]
+	RequestsTotal metric.Int64Counter
+
+	// Request duration histogram in seconds with [route]
+	RequestDuration metric.Float64Histogram
+}
+
+func newHTTPMetrics(meter metric.Meter) HTTPMetrics {
+	requestsTotal, _ := meter.Int64Counter(
+		"http_requests_total",
+		metric.WithDescription("Total number of HTTP requests"),
+	)
+	requestDuration, _ := meter.Float64Histogram(
+		"http_request_duration_seconds",
+		metric.WithDescription("HTTP request duration histogram in seconds"),
+		metric.WithExplicitBucketBoundaries(0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0),
+		metric.WithUnit("s"),
+	)
+	return HTTPMetrics{
+		RequestsTotal:   requestsTotal,
+		RequestDuration: requestDuration,
+	}
+}
+
+type ValueMetrics struct {
+	// Successful getValue lookups, with [code]. Only successful lookups carry a
+	// code label since the set of stored codes is bounded, unlike guessed/failed ones.
+	GetSuccessTotal metric.Int64Counter
+
+	// Failed getValue lookups, with [reason] (not_found|rate_limited).
+	GetFailedTotal metric.Int64Counter
+
+	// Successful setValue writes, with [user].
+	SetSuccessTotal metric.Int64Counter
+
+	// Failed setValue writes, with [reason] (bad_request|unauthorized).
+	SetFailedTotal metric.Int64Counter
+}
+
+func newValueMetrics(meter metric.Meter) ValueMetrics {
+	getSuccessTotal, _ := meter.Int64Counter(
+		"codevault_get_value_success_total",
+		metric.WithDescription("Total number of successful getValue lookups"),
+	)
+	getFailedTotal, _ := meter.Int64Counter(
+		"codevault_get_value_failed_total",
+		metric.WithDescription("Total number of failed getValue lookups"),
+	)
+	setSuccessTotal, _ := meter.Int64Counter(
+		"codevault_set_value_success_total",
+		metric.WithDescription("Total number of successful setValue writes"),
+	)
+	setFailedTotal, _ := meter.Int64Counter(
+		"codevault_set_value_failed_total",
+		metric.WithDescription("Total number of failed setValue writes"),
+	)
+	return ValueMetrics{
+		GetSuccessTotal: getSuccessTotal,
+		GetFailedTotal:  getFailedTotal,
+		SetSuccessTotal: setSuccessTotal,
+		SetFailedTotal:  setFailedTotal,
+	}
+}
+
+func addObservableMetrics(meter metric.Meter) {
+	timeStarted := time.Now()
+	_, _ = meter.Int64ObservableGauge(
+		"startup_time",
+		metric.WithDescription("Startup timestamp"),
+		metric.WithInt64Callback(func(ctx context.Context, io metric.Int64Observer) error {
+			io.Observe(timeStarted.Unix(), metric.WithAttributes(attribute.String("version", internal.Version)))
+			return nil
+		}),
+	)
+	_, _ = meter.Int64ObservableGauge(
+		"last_update_time",
+		metric.WithDescription("Current timestamp"),
+		metric.WithInt64Callback(func(ctx context.Context, io metric.Int64Observer) error {
+			io.Observe(time.Now().Unix(), metric.WithAttributes(attribute.String("version", internal.Version)))
+			return nil
+		}),
+	)
+}