Initial sleep on Retry-After (#539)

If the initial response to an LRO contains a Retry-After header, sleep
for the specified duration before beginning to poll.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # CHANGELOG
 
+## v14.2.1
+
+- In `Future.WaitForCompletionRef()`, if the initial async response includes a `Retry-After` header, sleep for the specified amount of time before starting to poll.
+
 ## v14.2.0
 
 - Added package comment to make `github.com/Azure/go-autorest` importable.

autorest/azure/async.go

@@ -167,7 +167,13 @@ func (f *Future) WaitForCompletionRef(ctx context.Context, client autorest.Clien
 		cancelCtx, cancel = context.WithTimeout(ctx, d)
 		defer cancel()
 	}
-
+	// if the initial response has a Retry-After, sleep for the specified amount of time before starting to poll
+	if delay, ok := f.GetPollingDelay(); ok {
+		if delayElapsed := autorest.DelayForBackoff(delay, 0, cancelCtx.Done()); !delayElapsed {
+			err = cancelCtx.Err()
+			return
+		}
+	}
 	done, err := f.DoneWithContext(ctx, client)
 	for attempts := 0; !done; done, err = f.DoneWithContext(ctx, client) {
 		if attempts >= client.RetryAttempts {

autorest/azure/async_test.go

@@ -745,6 +745,39 @@ func TestFuture_WaitForCompletionRef(t *testing.T) {
 		autorest.ByClosing())
 }
 
+func TestFuture_WaitForCompletionRefWithRetryAfter(t *testing.T) {
+	r2 := newOperationResourceResponse("busy")
+	r3 := newOperationResourceResponse(operationSucceeded)
+
+	sender := mocks.NewSender()
+	sender.AppendAndRepeatResponse(r2, 2)
+	sender.AppendResponse(r3)
+	client := autorest.Client{
+		PollingDelay:    1 * time.Second,
+		PollingDuration: autorest.DefaultPollingDuration,
+		RetryAttempts:   autorest.DefaultRetryAttempts,
+		RetryDuration:   1 * time.Second,
+		Sender:          sender,
+	}
+
+	future, err := NewFutureFromResponse(newSimpleAsyncRespWithRetryAfter())
+	if err != nil {
+		t.Fatalf("failed to create future: %v", err)
+	}
+
+	err = future.WaitForCompletionRef(context.Background(), client)
+	if err != nil {
+		t.Fatalf("WaitForCompletion returned non-nil error")
+	}
+
+	if sender.Attempts() < sender.NumResponses() {
+		t.Fatalf("stopped polling before receiving a terminated OperationResource")
+	}
+
+	autorest.Respond(future.Response(),
+		autorest.ByClosing())
+}
+
 func TestFuture_WaitForCompletionTimedOut(t *testing.T) {
 	r2 := newProvisioningStatusResponse("busy")
 
@@ -989,6 +1022,13 @@ func newSimpleAsyncResp() *http.Response {
 	return r
 }
 
+func newSimpleAsyncRespWithRetryAfter() *http.Response {
+	r := newAsyncResp(newAsyncReq(http.MethodPut, nil), http.StatusCreated, mocks.NewBody(fmt.Sprintf(operationResourceFormat, operationInProgress)))
+	mocks.SetResponseHeader(r, headerAsyncOperation, mocks.TestAzureAsyncURL)
+	mocks.SetResponseHeader(r, autorest.HeaderRetryAfter, "1")
+	return r
+}
+
 // creates a simple LRO response, POST/201 with Location header
 func newSimpleLocationResp() *http.Response {
 	r := newAsyncResp(newAsyncReq(http.MethodPost, nil), http.StatusCreated, mocks.NewBody(fmt.Sprintf(pollingStateFormat, operationInProgress)))

autorest/version.go

@@ -19,7 +19,7 @@ import (
 	"runtime"
 )
 
-const number = "v14.2.0"
+const number = "v14.2.1"
 
 var (
 	userAgent = fmt.Sprintf("Go/%s (%s-%s) go-autorest/%s",