Don't consider 408 as terminal failure for Location poller (#22674)

Treat 408 the same as 429, preserving state and returning the response.

sdk/azcore/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+* Pollers that use the `Location` header won't consider `http.StatusRequestTimeout` a terminal failure.
+
 ### Other Changes
 
 ## 1.11.0 (2024-04-01)

sdk/azcore/internal/pollers/loc/loc.go

@@ -103,10 +103,10 @@ func (p *Poller[T]) Poll(ctx context.Context) (*http.Response, error) {
 		} else if resp.StatusCode > 199 && resp.StatusCode < 300 {
 			// any 2xx other than a 202 indicates success
 			p.CurState = poller.StatusSucceeded
-		} else if resp.StatusCode == http.StatusTooManyRequests {
-			// the request is being throttled. DO NOT include
-			// this as a terminal failure. preserve the
-			// existing state and return the response.
+		} else if resp.StatusCode == http.StatusRequestTimeout || resp.StatusCode == http.StatusTooManyRequests {
+			// the request timed out or is being throttled.
+			// DO NOT include this as a terminal failure. preserve
+			// the existing state and return the response.
 		} else {
 			p.CurState = poller.StatusFailed
 		}

sdk/azcore/internal/pollers/loc/loc_test.go

@@ -197,3 +197,26 @@ func TestWithThrottling(t *testing.T) {
 	require.EqualValues(t, 4, respCount)
 	require.EqualValues(t, poller.StatusSucceeded, lp.CurState)
 }
+
+func TestWithTimeout(t *testing.T) {
+	srv, close := mock.NewServer()
+	defer close()
+	srv.AppendResponse(mock.WithStatusCode(http.StatusAccepted))
+	srv.AppendResponse(mock.WithStatusCode(http.StatusRequestTimeout))
+	srv.AppendResponse(mock.WithStatusCode(http.StatusRequestTimeout))
+	srv.AppendResponse(mock.WithStatusCode(http.StatusOK))
+	resp := initialResponse()
+	resp.Header.Set(shared.HeaderLocation, srv.URL())
+	lp, err := New[struct{}](exported.NewPipeline(shared.TransportFunc(func(req *http.Request) (*http.Response, error) {
+		return srv.Do(req)
+	})), resp)
+	require.NoError(t, err)
+	respCount := 0
+	for !lp.Done() {
+		_, err = lp.Poll(context.Background())
+		require.NoError(t, err)
+		respCount++
+	}
+	require.EqualValues(t, 4, respCount)
+	require.EqualValues(t, poller.StatusSucceeded, lp.CurState)
+}