close stream and log error instead of fatal

Summary:
instead of crashing when receiving stream when starting it logs and error message and closes the stream

#build_more

Reviewed By: nomiero

Differential Revision: D66776869

fbshipit-source-id: 86a1ef92a03c7eb803e7a3c9c4dd42fa3a41ab63

third-party/thrift/src/thrift/lib/cpp2/async/ServerGeneratorStream-inl.h

@@ -119,9 +119,13 @@ ServerStreamFn<T> ServerGeneratorStream::fromAsyncGenerator(
           std::move(gen),
           TileStreamGuard::transferFrom(std::move(interaction)))
           .scheduleOn(std::move(serverExecutor))
-          .start([](folly::Try<folly::Unit> t) {
+          .start([sp = stream->copy()](folly::Try<folly::Unit> t) {
             if (t.hasException()) {
-              LOG(FATAL) << t.exception();
+              LOG(ERROR)
+                  << "Closing Stream because it received an exception before it started: "
+                  << std::endl
+                  << t.exception();
+              sp->close();
             }
           });
       std::ignore =