Open telemetry integration (#3972)

This PR adds opentelemetry and chi wrapper to have basic instrumentation

<!--start release-notes-assistant-->

## 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_test.go

@@ -0,0 +1,114 @@
+// Copyright 2024 TheFox0x7. All rights reserved.
+// SPDX-License-Identifier: EUPL-1.2
+
+package opentelemetry
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"testing"
+	"time"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+func TestTraceGrpcExporter(t *testing.T) {
+	grpcMethods := make(chan string)
+	tlsConfig := generateTestTLS(t, os.TempDir(), "localhost,127.0.0.1")
+	assert.NotNil(t, tlsConfig)
+
+	collector := grpc.NewServer(grpc.Creds(credentials.NewTLS(tlsConfig)), grpc.UnknownServiceHandler(func(srv any, stream grpc.ServerStream) error {
+		method, _ := grpc.Method(stream.Context())
+		grpcMethods <- method
+		return nil
+	}))
+	defer collector.GracefulStop()
+	ln, err := net.Listen("tcp", "localhost:0")
+	require.NoError(t, err)
+	defer ln.Close()
+	go collector.Serve(ln)
+
+	traceEndpoint, err := url.Parse("https://" + ln.Addr().String())
+	require.NoError(t, err)
+	config := &setting.OtelExporter{
+		Endpoint:          traceEndpoint,
+		Certificate:       os.TempDir() + "/cert.pem",
+		ClientCertificate: os.TempDir() + "/cert.pem",
+		ClientKey:         os.TempDir() + "/key.pem",
+		Protocol:          "grpc",
+	}
+
+	defer test.MockVariableValue(&setting.OpenTelemetry.ServiceName, "forgejo-certs")()
+	defer test.MockVariableValue(&setting.OpenTelemetry.Enabled, true)()
+	defer test.MockVariableValue(&setting.OpenTelemetry.Traces, "otlp")()
+	defer test.MockVariableValue(&setting.OpenTelemetry.OtelTraces, config)()
+	ctx := context.Background()
+	require.NoError(t, Init(ctx))
+
+	tracer := otel.Tracer("test_tls")
+	_, span := tracer.Start(ctx, "test span")
+	assert.True(t, span.SpanContext().HasTraceID())
+	assert.True(t, span.SpanContext().HasSpanID())
+
+	span.End()
+	// Give the exporter time to send the span
+	select {
+	case method := <-grpcMethods:
+		assert.Equal(t, "/opentelemetry.proto.collector.trace.v1.TraceService/Export", method)
+	case <-time.After(10 * time.Second):
+		t.Fatal("no grpc call within 10s")
+	}
+}
+
+func TestTraceHttpExporter(t *testing.T) {
+	httpCalls := make(chan string)
+	tlsConfig := generateTestTLS(t, os.TempDir(), "localhost,127.0.0.1")
+	assert.NotNil(t, tlsConfig)
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		httpCalls <- r.URL.Path
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"success": true}`))
+	}))
+	server.TLS = tlsConfig
+
+	traceEndpoint, err := url.Parse("http://" + server.Listener.Addr().String())
+	require.NoError(t, err)
+	config := &setting.OtelExporter{
+		Endpoint:          traceEndpoint,
+		Certificate:       os.TempDir() + "/cert.pem",
+		ClientCertificate: os.TempDir() + "/cert.pem",
+		ClientKey:         os.TempDir() + "/key.pem",
+		Protocol:          "http/protobuf",
+	}
+
+	defer test.MockVariableValue(&setting.OpenTelemetry.ServiceName, "forgejo-certs")()
+	defer test.MockVariableValue(&setting.OpenTelemetry.Enabled, true)()
+	defer test.MockVariableValue(&setting.OpenTelemetry.Traces, "otlp")()
+	defer test.MockVariableValue(&setting.OpenTelemetry.OtelTraces, config)()
+	ctx := context.Background()
+	require.NoError(t, Init(ctx))
+
+	tracer := otel.Tracer("test_tls")
+	_, span := tracer.Start(ctx, "test span")
+	assert.True(t, span.SpanContext().HasTraceID())
+	assert.True(t, span.SpanContext().HasSpanID())
+
+	span.End()
+	select {
+	case path := <-httpCalls:
+		assert.Equal(t, "/v1/traces", path)
+	case <-time.After(10 * time.Second):
+		t.Fatal("no http call within 10s")
+	}
+}