add bad example

Author: shijiesheng

workflow/context.go

@@ -21,6 +21,8 @@
 package workflow
 
 import (
+	"fmt"
+
 	"github.com/opentracing/opentracing-go"
 	"go.uber.org/cadence/internal"
 )
@@ -98,21 +100,42 @@ func GetSpanContext(ctx Context) opentracing.SpanContext {
 // This is useful to modify baggage items of current workflow and pass it to activities and child workflows.
 //
 // Example Usage:
-//	func myWorkflow(ctx Context) error {
-// 		// start a new workflow span
-// 		wSpan := opentracing.StartSpan("workflow-operation", opentracing.ChildOf(spanContext))
-// 		// pass the new span context to activity
-// 		aCtx := WithSpanContext(ctx, wSpan.Context())
-// 		var activityFooResult string
-// 		err := ExecuteActivity(aCtx, ActivityFoo).Get(aCtx, &activityFooResult)
-// 		if err != nil {
-// 			wSpan.SetTag("workflow-error", err)
-// 		} else {
-// 			wSpan.SetTag("workflow-result", activityFooResult)
-// 		}
-// 		wSpan.Finish()
-// 		return activityFooResult, err
+// func goodWorkflow(ctx Context) (string, error) {
+// 	// start a short lived new workflow span within SideEffect to avoid duplicate span creation during replay
+// 	spanContextValue := SideEffect(ctx, func(ctx Context) interface{} {
+// 		wSpan := opentracing.StartSpan("workflow-operation-with-new-span", opentracing.ChildOf(GetSpanContext(ctx)))
+// 		defer wSpan.Finish()
+// 		wSpan.SetTag("some-key", "some-value")
+// 		return wSpan.Context()
+// 	})
+// 	var spanContext opentracing.SpanContext
+// 	err := spanContextValue.Get(&spanContext)
+// 	if err != nil {
+// 		return "",fmt.Errorf("failed to get span context: %w", err)
 // 	}
+//
+// 	aCtx := WithSpanContext(ctx, spanContext)
+// 	var activityFooResult string
+// 	err = ExecuteActivity(aCtx, activityFoo).Get(aCtx, &activityFooResult)
+// 	return activityFooResult, err
+// }
+//
+// Bad Example:
+// func badWorkflow(ctx Context) (string, error) {
+// 	// start a new workflow span for EVERY REPLAY
+// 	wSpan := opentracing.StartSpan("workflow-operation", opentracing.ChildOf(GetSpanContext(ctx)))
+// 	wSpan.SetBaggageItem("some-key", "some-value")
+// 	// pass the new span context to activity
+// 	aCtx := WithSpanContext(ctx, wSpan.Context())
+// 	var activityFooResult string
+// 	err := ExecuteActivity(aCtx, activityFoo).Get(aCtx, &activityFooResult)
+// 	wSpan.Finish()
+// 	return activityFooResult, err
+// }
+//
+// func activityFoo(ctx Context) (string, error) {
+// 	return "activity-foo-result", nil
+// }
 func WithSpanContext(ctx Context, spanContext opentracing.SpanContext) Context {
 	return internal.WithSpanContext(ctx, spanContext)
 }