feat(tvix/store/nar-bridge): Setup OpenTelemetry r/7442

Sets up OpenTelemetry integration for nar-bridge. Right now it will
export spans for HTTP server requests and all gRPC client requests.
Having the spans available will make performance work significantly
easier as it provides a high level overview of where time is being
spent.

In the future we can add application-specifc metrics and
integrate logrus.

Change-Id: Ie3860675d7ffc626a95673ba062c3c798d8bb2a7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10678
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: Connor Brewster <cbrewster@hey.com>

1 files changed, 87 insertions, 0 deletions

diff --git a/tvix/nar-bridge/cmd/nar-bridge-http/otel.go b/tvix/nar-bridge/cmd/nar-bridge-http/otel.go
new file mode 100644
index 000000000000..c446c6ec1a14
--- /dev/null
+++ b/tvix/nar-bridge/cmd/nar-bridge-http/otel.go
@@ -0,0 +1,87 @@
+package main
+
+import (
+	"context"
+	"errors"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
+	"go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+)
+
+func setupOpenTelemetry(ctx context.Context, serviceName, serviceVersion string) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	res, err := resource.Merge(
+		resource.Default(),
+		resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceName(serviceName),
+			semconv.ServiceVersion(serviceVersion),
+		),
+	)
+	if err != nil {
+		return nil, errors.Join(err, shutdown(ctx))
+	}
+
+	prop := propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+	otel.SetTextMapPropagator(prop)
+
+	tracerProvider, err := newTraceProvider(ctx, res)
+	if err != nil {
+		return nil, errors.Join(err, shutdown(ctx))
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	meterProvider, err := newMeterProvider(ctx, res)
+	if err != nil {
+		return nil, errors.Join(err, shutdown(ctx))
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	return shutdown, nil
+}
+
+func newTraceProvider(ctx context.Context, res *resource.Resource) (*trace.TracerProvider, error) {
+	traceExporter, err := otlptracegrpc.New(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	traceProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter),
+		trace.WithResource(res),
+	)
+	return traceProvider, nil
+}
+
+func newMeterProvider(ctx context.Context, res *resource.Resource) (*metric.MeterProvider, error) {
+	metricExporter, err := otlpmetricgrpc.New(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	meterProvider := metric.NewMeterProvider(
+		metric.WithResource(res),
+		metric.WithReader(metric.NewPeriodicReader(metricExporter)),
+	)
+	return meterProvider, nil
+}