Dynamically expand timeout when waiting for Angular CLI to be ready. Fixes aspnet#1611

SteveSandersonMS · SteveSandersonMS · commit 4d151a599e28 · 2018-04-16T14:54:52.000+01:00
diff --git a/src/Microsoft.AspNetCore.SpaServices.Extensions/AngularCli/AngularCliMiddleware.cs b/src/Microsoft.AspNetCore.SpaServices.Extensions/AngularCli/AngularCliMiddleware.cs
@@ -105,6 +105,7 @@ private static async Task WaitForAngularCliServerToAcceptRequests(Uri cliServerU
             // connection then it's not ready. We keep trying forever because this is dev-mode
             // only, and only a single startup attempt will be made, and there's a further level
             // of timeouts enforced on a per-request basis.
+            var timeoutMilliseconds = 1000;
             using (var client = new HttpClient())
             {
                 while (true)
@@ -114,12 +115,23 @@ private static async Task WaitForAngularCliServerToAcceptRequests(Uri cliServerU
                         // If we get any HTTP response, the CLI server is ready
                         await client.SendAsync(
                             new HttpRequestMessage(HttpMethod.Head, cliServerUri),
-                            new CancellationTokenSource(1000).Token);
+                            new CancellationTokenSource(timeoutMilliseconds).Token);
                         return;
                     }
                     catch (Exception)
                     {
-                        await Task.Delay(1000); // 1 second
+                        await Task.Delay(500);
+
+                        // Depending on the host's networking configuration, the requests can take a while
+                        // to go through, most likely due to the time spent resolving 'localhost'.
+                        // Each time we have a failure, allow a bit longer next time (up to a maximum).
+                        // This only influences the time until we regard the dev server as 'ready', so it
+                        // doesn't affect the runtime perf (even in dev mode) once the first connection is made.
+                        // Resolves https://github.com/aspnet/JavaScriptServices/issues/1611
+                        if (timeoutMilliseconds < 10000)
+                        {
+                            timeoutMilliseconds += 3000;
+                        }
                     }
                 }
             }

Original file line number	Diff line number	Diff line change
`@@ -105,6 +105,7 @@ private static async Task WaitForAngularCliServerToAcceptRequests(Uri cliServerU`
`105`	`105`	`// connection then it's not ready. We keep trying forever because this is dev-mode`
`106`	`106`	`// only, and only a single startup attempt will be made, and there's a further level`
`107`	`107`	`// of timeouts enforced on a per-request basis.`
	`108`	`+ var timeoutMilliseconds = 1000;`
`108`	`109`	`using (var client = new HttpClient())`
`109`	`110`	`{`
`110`	`111`	`while (true)`
`@@ -114,12 +115,23 @@ private static async Task WaitForAngularCliServerToAcceptRequests(Uri cliServerU`
`114`	`115`	`// If we get any HTTP response, the CLI server is ready`
`115`	`116`	`await client.SendAsync(`
`116`	`117`	`new HttpRequestMessage(HttpMethod.Head, cliServerUri),`
`117`		`- new CancellationTokenSource(1000).Token);`
	`118`	`+ new CancellationTokenSource(timeoutMilliseconds).Token);`
`118`	`119`	`return;`
`119`	`120`	`}`
`120`	`121`	`catch (Exception)`
`121`	`122`	`{`
`122`		`- await Task.Delay(1000); // 1 second`
	`123`	`+ await Task.Delay(500);`
	`124`	`+`
	`125`	`+ // Depending on the host's networking configuration, the requests can take a while`
	`126`	`+ // to go through, most likely due to the time spent resolving 'localhost'.`
	`127`	`+ // Each time we have a failure, allow a bit longer next time (up to a maximum).`
	`128`	`+ // This only influences the time until we regard the dev server as 'ready', so it`
	`129`	`+ // doesn't affect the runtime perf (even in dev mode) once the first connection is made.`
	`130`	`+ // Resolves https://github.com/aspnet/JavaScriptServices/issues/1611`
	`131`	`+ if (timeoutMilliseconds < 10000)`
	`132`	`+ {`
	`133`	`+ timeoutMilliseconds += 3000;`
	`134`	`+ }`
`123`	`135`	`}`
`124`	`136`	`}`
`125`	`137`	`}`