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/otel_test.go

@@ -0,0 +1,121 @@
+// Copyright 2024 TheFox0x7. All rights reserved.
+// SPDX-License-Identifier: EUPL-1.2
+
+package opentelemetry
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"net"
+	"os"
+	"strings"
+	"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"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/sdk/trace/tracetest"
+)
+
+func TestNoopDefault(t *testing.T) {
+	inMem := tracetest.NewInMemoryExporter()
+	called := false
+	exp := func(ctx context.Context) (sdktrace.SpanExporter, error) {
+		called = true
+		return inMem, nil
+	}
+	exporter["inmemory"] = exp
+	t.Cleanup(func() {
+		delete(exporter, "inmemory")
+	})
+	defer test.MockVariableValue(&setting.OpenTelemetry.Traces, "inmemory")
+
+	ctx := context.Background()
+	require.NoError(t, Init(ctx))
+	tracer := otel.Tracer("test_noop")
+
+	_, span := tracer.Start(ctx, "test span")
+	defer span.End()
+
+	assert.False(t, span.SpanContext().HasTraceID())
+	assert.False(t, span.SpanContext().HasSpanID())
+	assert.False(t, called)
+}
+
+func generateTestTLS(t *testing.T, path, host string) *tls.Config {
+	_, priv, err := ed25519.GenerateKey(rand.Reader)
+	require.NoError(t, err, "Failed to generate private key: %v", err)
+
+	keyUsage := x509.KeyUsageDigitalSignature
+
+	notBefore := time.Now()
+	notAfter := notBefore.Add(time.Hour)
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	require.NoError(t, err, "Failed to generate serial number: %v", err)
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			Organization: []string{"Forgejo Testing"},
+		},
+		NotBefore: notBefore,
+		NotAfter:  notAfter,
+
+		KeyUsage:              keyUsage,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
+		BasicConstraintsValid: true,
+	}
+
+	hosts := strings.Split(host, ",")
+	for _, h := range hosts {
+		if ip := net.ParseIP(h); ip != nil {
+			template.IPAddresses = append(template.IPAddresses, ip)
+		} else {
+			template.DNSNames = append(template.DNSNames, h)
+		}
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, priv.Public(), priv)
+	require.NoError(t, err, "Failed to create certificate: %v", err)
+
+	certOut, err := os.Create(path + "/cert.pem")
+	require.NoError(t, err, "Failed to open cert.pem for writing: %v", err)
+
+	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
+		t.Fatalf("Failed to write data to cert.pem: %v", err)
+	}
+	if err := certOut.Close(); err != nil {
+		t.Fatalf("Error closing cert.pem: %v", err)
+	}
+	keyOut, err := os.OpenFile(path+"/key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
+	require.NoError(t, err, "Failed to open key.pem for writing: %v", err)
+
+	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
+	require.NoError(t, err, "Unable to marshal private key: %v", err)
+
+	if err := pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
+		t.Fatalf("Failed to write data to key.pem: %v", err)
+	}
+	if err := keyOut.Close(); err != nil {
+		t.Fatalf("Error closing key.pem: %v", err)
+	}
+	serverCert, err := tls.LoadX509KeyPair(path+"/cert.pem", path+"/key.pem")
+	require.NoError(t, err, "failed to load the key pair")
+	return &tls.Config{
+		Certificates: []tls.Certificate{serverCert},
+		ClientAuth:   tls.RequireAnyClientCert,
+	}
+}