Open telemetry integration (#3972)

This PR adds opentelemetry and chi wrapper to have basic instrumentation

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## Draft release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/3972): <!--number 3972 --><!--line 0 --><!--description YWRkIHN1cHBvcnQgZm9yIGJhc2ljIHJlcXVlc3QgdHJhY2luZyB3aXRoIG9wZW50ZWxlbWV0cnk=-->add support for basic request tracing with opentelemetry<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/3972
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: TheFox0x7 <thefox0x7@gmail.com>
Co-committed-by: TheFox0x7 <thefox0x7@gmail.com>

modules/opentelemetry/traces.go

@@ -0,0 +1,98 @@
+// Copyright 2024 TheFox0x7. All rights reserved.
+// SPDX-License-Identifier: EUPL-1.2
+
+package opentelemetry
+
+import (
+	"context"
+	"crypto/tls"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	"google.golang.org/grpc/credentials"
+)
+
+func newGrpcExporter(ctx context.Context) (sdktrace.SpanExporter, error) {
+	endpoint := setting.OpenTelemetry.OtelTraces.Endpoint
+
+	opts := []otlptracegrpc.Option{}
+
+	tlsConf := &tls.Config{}
+	opts = append(opts, otlptracegrpc.WithEndpoint(endpoint.Host))
+	opts = append(opts, otlptracegrpc.WithTimeout(setting.OpenTelemetry.OtelTraces.Timeout))
+	switch setting.OpenTelemetry.OtelTraces.Endpoint.Scheme {
+	case "http", "unix":
+		opts = append(opts, otlptracegrpc.WithInsecure())
+	}
+
+	if setting.OpenTelemetry.OtelTraces.Compression != "" {
+		opts = append(opts, otlptracegrpc.WithCompressor(setting.OpenTelemetry.OtelTraces.Compression))
+	}
+	withCertPool(setting.OpenTelemetry.OtelTraces.Certificate, tlsConf)
+	withClientCert(setting.OpenTelemetry.OtelTraces.ClientCertificate, setting.OpenTelemetry.OtelTraces.ClientKey, tlsConf)
+	if tlsConf.RootCAs != nil || len(tlsConf.Certificates) > 0 {
+		opts = append(opts, otlptracegrpc.WithTLSCredentials(
+			credentials.NewTLS(tlsConf),
+		))
+	}
+	opts = append(opts, otlptracegrpc.WithHeaders(setting.OpenTelemetry.OtelTraces.Headers))
+
+	return otlptracegrpc.New(ctx, opts...)
+}
+
+func newHTTPExporter(ctx context.Context) (sdktrace.SpanExporter, error) {
+	endpoint := setting.OpenTelemetry.OtelTraces.Endpoint
+	opts := []otlptracehttp.Option{}
+	tlsConf := &tls.Config{}
+	opts = append(opts, otlptracehttp.WithEndpoint(endpoint.Host))
+	switch setting.OpenTelemetry.OtelTraces.Endpoint.Scheme {
+	case "http", "unix":
+		opts = append(opts, otlptracehttp.WithInsecure())
+	}
+	switch setting.OpenTelemetry.OtelTraces.Compression {
+	case "gzip":
+		opts = append(opts, otlptracehttp.WithCompression(otlptracehttp.GzipCompression))
+	default:
+		opts = append(opts, otlptracehttp.WithCompression(otlptracehttp.NoCompression))
+	}
+	withCertPool(setting.OpenTelemetry.OtelTraces.Certificate, tlsConf)
+	withClientCert(setting.OpenTelemetry.OtelTraces.ClientCertificate, setting.OpenTelemetry.OtelTraces.ClientKey, tlsConf)
+	if tlsConf.RootCAs != nil || len(tlsConf.Certificates) > 0 {
+		opts = append(opts, otlptracehttp.WithTLSClientConfig(tlsConf))
+	}
+	opts = append(opts, otlptracehttp.WithHeaders(setting.OpenTelemetry.OtelTraces.Headers))
+
+	return otlptracehttp.New(ctx, opts...)
+}
+
+var exporter = map[string]func(context.Context) (sdktrace.SpanExporter, error){
+	"http/protobuf": newHTTPExporter,
+	"grpc":          newGrpcExporter,
+}
+
+// Create new and register trace provider from user defined configuration
+func setupTraceProvider(ctx context.Context, r *resource.Resource) (func(context.Context) error, error) {
+	var shutdown func(context.Context) error
+	switch setting.OpenTelemetry.Traces {
+	case "otlp":
+		traceExporter, err := exporter[setting.OpenTelemetry.OtelTraces.Protocol](ctx)
+		if err != nil {
+			return nil, err
+		}
+		traceProvider := sdktrace.NewTracerProvider(
+			sdktrace.WithSampler(setting.OpenTelemetry.Sampler),
+			sdktrace.WithBatcher(traceExporter),
+			sdktrace.WithResource(r),
+		)
+		otel.SetTracerProvider(traceProvider)
+		shutdown = traceProvider.Shutdown
+	default:
+		shutdown = func(ctx context.Context) error { return nil }
+	}
+	return shutdown, nil
+}