move implementation to internal/ directory (#828)

internal/daemon/logging/trace/trace_convenience.go

@@ -0,0 +1,76 @@
+package trace
+
+import (
+	"context"
+	"fmt"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+// use like this:
+//
+//	defer WithSpanFromStackUpdateCtx(&existingCtx)()
+func WithSpanFromStackUpdateCtx(ctx *context.Context) DoneFunc {
+	childSpanCtx, end := WithSpan(*ctx, getMyCallerOrPanic())
+	*ctx = childSpanCtx
+	return end
+}
+
+// derive task name from call stack (caller's name)
+func WithTaskFromStack(ctx context.Context) (context.Context, DoneFunc) {
+	return WithTask(ctx, getMyCallerOrPanic())
+}
+
+// derive task name from call stack (caller's name) and update *ctx
+// to point to be the child task ctx
+func WithTaskFromStackUpdateCtx(ctx *context.Context) DoneFunc {
+	child, end := WithTask(*ctx, getMyCallerOrPanic())
+	*ctx = child
+	return end
+}
+
+// create a task and a span within it in one call
+func WithTaskAndSpan(ctx context.Context, task string, span string) (context.Context, DoneFunc) {
+	ctx, endTask := WithTask(ctx, task)
+	ctx, endSpan := WithSpan(ctx, fmt.Sprintf("%s %s", task, span))
+	return ctx, func() {
+		endSpan()
+		endTask()
+	}
+}
+
+// create a span during which several child tasks are spawned using the `add` function
+//
+// IMPORTANT FOR USERS: Caller must ensure that the capturing behavior is correct, the Go linter doesn't catch this.
+func WithTaskGroup(ctx context.Context, taskGroup string) (_ context.Context, add func(f func(context.Context)), waitEnd DoneFunc) {
+	var wg sync.WaitGroup
+	ctx, endSpan := WithSpan(ctx, taskGroup)
+	add = func(f func(context.Context)) {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			ctx, endTask := WithTask(ctx, taskGroup)
+			defer endTask()
+			f(ctx)
+		}()
+	}
+	waitEnd = func() {
+		wg.Wait()
+		endSpan()
+	}
+	return ctx, add, waitEnd
+}
+
+func getMyCallerOrPanic() string {
+	pc, _, _, ok := runtime.Caller(2)
+	if !ok {
+		panic("cannot get caller")
+	}
+	details := runtime.FuncForPC(pc)
+	if ok && details != nil {
+		const prefix = "github.com/zrepl/zrepl"
+		return strings.TrimPrefix(strings.TrimPrefix(details.Name(), prefix), "/")
+	}
+	return ""
+}