Add basic runtime tracing (#2996)

This allows us in almost all places to use regions to further trace down
long running tasks.
Also removes an unused function.

internal/tracing.go

@@ -0,0 +1,64 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"context"
+	"runtime/trace"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+type Trace struct {
+	span   opentracing.Span
+	region *trace.Region
+	task   *trace.Task
+}
+
+func StartTask(inCtx context.Context, name string) (Trace, context.Context) {
+	ctx, task := trace.NewTask(inCtx, name)
+	span, ctx := opentracing.StartSpanFromContext(ctx, name)
+	return Trace{
+		span: span,
+		task: task,
+	}, ctx
+}
+
+func StartRegion(inCtx context.Context, name string) (Trace, context.Context) {
+	region := trace.StartRegion(inCtx, name)
+	span, ctx := opentracing.StartSpanFromContext(inCtx, name)
+	return Trace{
+		span:   span,
+		region: region,
+	}, ctx
+}
+
+func (t Trace) EndRegion() {
+	t.span.Finish()
+	if t.region != nil {
+		t.region.End()
+	}
+}
+
+func (t Trace) EndTask() {
+	t.span.Finish()
+	if t.task != nil {
+		t.task.End()
+	}
+}
+
+func (t Trace) SetTag(key string, value any) {
+	t.span.SetTag(key, value)
+}