Use timeout to read most recent build from http

tools/gardening/lib/src/util.dart

Index: tools/gardening/lib/src/util.dart
diff --git a/tools/gardening/lib/src/util.dart b/tools/gardening/lib/src/util.dart
index 51b50c1e3dec79d037401a16254d3a4046ee07ee..108fffcb98d4867c62e33d22b2c5b99fb1202bb1 100644
--- a/tools/gardening/lib/src/util.dart
+++ b/tools/gardening/lib/src/util.dart
@@ -64,15 +64,39 @@ class HttpException implements Exception {
   String toString() => '$uri: $statusCode';
 }
 
+class TimeoutException implements Exception {

[floitsch, 2017/08/15 11:26:35]

I would have used the builtin TimeoutException class.

It doesn't have a uri field, but it doesn't look like that one is used anyway.

[Johnni Winther, 2017/08/15 12:51:27]

Done.

+  final Uri uri;
+
+  TimeoutException(this.uri);
+
+  String toString() => '$uri timeout';
+}
+
 /// Reads the content of [uri] as text.
-Future<String> readUriAsText(HttpClient client, Uri uri) async {
+Future<String> readUriAsText(
+    HttpClient client, Uri uri, Duration timeout) async {
   HttpClientRequest request = await client.getUrl(uri);
   HttpClientResponse response = await request.close();
   if (response.statusCode != 200) {
     response.drain();
     throw new HttpException(uri, response.statusCode);
   }
-  return response.transform(UTF8.decoder).join();
+  List<int> data = <int>[];
+  Timer timer;
+  Completer<String> completer = new Completer<String>();
+  StreamSubscription subscription = response.listen((List<int> buffer) {

[floitsch, 2017/08/15 11:26:35]

You could consider using .timeout from the Stream class.

return response
    .timeout(timeout)
    .toList()
    .then((chunks) => chunks.expand((x) => x).toList());


The expand might be too expensive, but then you could just do a small loop in
the .then (calling `addAll` on a fresh list.

[Johnni Winther, 2017/08/15 12:51:27]

Done.

+    data.addAll(buffer);
+  }, onDone: () {
+    timer?.cancel();
+    completer.complete(UTF8.decode(data));
+  }, cancelOnError: true);
+  if (timeout != null) {
+    timer = new Timer(timeout, () {
+      subscription.cancel();
+      completer.completeError(new TimeoutException(uri));
+    });
+  }
+  return completer.future;
 }
 
 ArgParser createArgParser() {