1 files changed, 182 insertions, 0 deletions
diff --git a/internal/observability/tracing.go b/internal/observability/tracing.go
new file mode 100644
index 000000000..7827004a3
--- /dev/null
+++ b/internal/observability/tracing.go
@@ -0,0 +1,182 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !nootel
+
+package observability
+
+import (
+	"context"
+	"fmt"
+
+	"codeberg.org/gruf/go-kv"
+	"github.com/gin-gonic/gin"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/resource"
+	"go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/semconv/v1.20.0/httpconv"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+	oteltrace "go.opentelemetry.io/otel/trace"
+
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+const (
+	tracerKey  = "gotosocial-server-tracer"
+	tracerName = "github.com/superseriousbusiness/gotosocial/internal/observability"
+)
+
+func InitializeTracing() error {
+	if !config.GetTracingEnabled() {
+		return nil
+	}
+
+	insecure := config.GetTracingInsecureTransport()
+
+	var tpo trace.TracerProviderOption
+	switch config.GetTracingTransport() {
+	case "grpc":
+		opts := []otlptracegrpc.Option{
+			otlptracegrpc.WithEndpoint(config.GetTracingEndpoint()),
+		}
+		if insecure {
+			opts = append(opts, otlptracegrpc.WithInsecure())
+		}
+		exp, err := otlptracegrpc.New(context.Background(), opts...)
+		if err != nil {
+			return fmt.Errorf("building tracing exporter: %w", err)
+		}
+		tpo = trace.WithBatcher(exp)
+	case "http":
+		opts := []otlptracehttp.Option{
+			otlptracehttp.WithEndpoint(config.GetTracingEndpoint()),
+		}
+		if insecure {
+			opts = append(opts, otlptracehttp.WithInsecure())
+		}
+		exp, err := otlptracehttp.New(context.Background(), opts...)
+		if err != nil {
+			return fmt.Errorf("building tracing exporter: %w", err)
+		}
+		tpo = trace.WithBatcher(exp)
+	default:
+		return fmt.Errorf("invalid tracing transport: %s", config.GetTracingTransport())
+	}
+	r, err := resource.Merge(
+		resource.Default(),
+		resource.NewSchemaless(
+			semconv.ServiceName("GoToSocial"),
+			semconv.ServiceVersion(config.GetSoftwareVersion()),
+		),
+	)
+	if err != nil {
+		// this can happen if semconv versioning is out-of-sync
+		return fmt.Errorf("building tracing resource: %w", err)
+	}
+
+	tp := trace.NewTracerProvider(
+		tpo,
+		trace.WithResource(r),
+	)
+	otel.SetTracerProvider(tp)
+	propagator := propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+	otel.SetTextMapPropagator(propagator)
+	log.Hook(func(ctx context.Context, kvs []kv.Field) []kv.Field {
+		span := oteltrace.SpanFromContext(ctx)
+		if span != nil && span.SpanContext().HasTraceID() {
+			return append(kvs, kv.Field{K: "traceID", V: span.SpanContext().TraceID().String()})
+		}
+		return kvs
+	})
+	return nil
+}
+
+// InstrumentGin is a middleware injecting tracing information based on the
+// otelgin implementation found at
+// https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/instrumentation/github.com/gin-gonic/gin/otelgin/gintrace.go
+func TracingMiddleware() gin.HandlerFunc {
+	provider := otel.GetTracerProvider()
+	tracer := provider.Tracer(
+		tracerName,
+		oteltrace.WithInstrumentationVersion(config.GetSoftwareVersion()),
+	)
+	propagator := otel.GetTextMapPropagator()
+	return func(c *gin.Context) {
+		spanName := c.FullPath()
+		// Do not trace a request if it didn't match a route. This doesn't omit
+		// all 404s as a request matching /:user for a user that doesn't exist
+		// still matches the route
+		if spanName == "" {
+			c.Next()
+			return
+		}
+
+		c.Set(tracerKey, tracer)
+		savedCtx := c.Request.Context()
+		defer func() {
+			c.Request = c.Request.WithContext(savedCtx)
+		}()
+		ctx := propagator.Extract(savedCtx, propagation.HeaderCarrier(c.Request.Header))
+		opts := []oteltrace.SpanStartOption{
+			oteltrace.WithAttributes(httpconv.ServerRequest(config.GetHost(), c.Request)...),
+			oteltrace.WithSpanKind(oteltrace.SpanKindServer),
+		}
+
+		rAttr := semconv.HTTPRoute(spanName)
+		opts = append(opts, oteltrace.WithAttributes(rAttr))
+		id := gtscontext.RequestID(c.Request.Context())
+		if id != "" {
+			opts = append(opts, oteltrace.WithAttributes(attribute.String("requestID", id)))
+		}
+		ctx, span := tracer.Start(ctx, spanName, opts...)
+		defer span.End()
+
+		// pass the span through the request context
+		c.Request = c.Request.WithContext(ctx)
+
+		// serve the request to the next middleware
+		c.Next()
+
+		status := c.Writer.Status()
+		span.SetStatus(httpconv.ServerStatus(status))
+		if status > 0 {
+			span.SetAttributes(semconv.HTTPResponseStatusCode(status))
+		}
+		if len(c.Errors) > 0 {
+			span.SetAttributes(attribute.String("gin.errors", c.Errors.String()))
+		}
+	}
+}
+
+func InjectRequestID() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		id := gtscontext.RequestID(c.Request.Context())
+		if id != "" {
+			span := oteltrace.SpanFromContext(c.Request.Context())
+			span.SetAttributes(attribute.String("requestID", id))
+		}
+	}
+}