Merge pull request #2971 from KoenRijpstra/fix/early-connection-window-update

Fix: send connection-level WINDOW_UPDATE at session start

Author: murgatroid99

packages/grpc-js/src/transport.ts

@@ -719,14 +719,33 @@ export class Http2SubchannelConnector implements SubchannelConnector {
  settings: {
  initialWindowSize:
  options['grpc-node.flow_control_window'] ??
- http2.getDefaultSettings().initialWindowSize,
+ http2.getDefaultSettings().initialWindowSize ?? 65535,
  }
  });
+
+ // Prepare window size configuration for remoteSettings handler
+ const defaultWin = http2.getDefaultSettings().initialWindowSize ?? 65535; // 65 535 B
+ const connWin = options[
+ 'grpc-node.flow_control_window'
+ ] as number | undefined;
+
  this.session = session;
  let errorMessage = 'Failed to connect';
  let reportedError = false;
  session.unref();
  session.once('remoteSettings', () => {
+ // Send WINDOW_UPDATE now to avoid 65 KB start-window stall.
+ if (connWin && connWin > defaultWin) {
+ try {
+ // Node ≥ 14.18
+ (session as any).setLocalWindowSize(connWin);
+ } catch {
+ // Older Node: bump by the delta
+ const delta = connWin - (session.state.localWindowSize ?? defaultWin);
+ if (delta > 0) (session as any).incrementWindowSize(delta);
+ }
+ }
+ 
  session.removeAllListeners();
  secureConnectResult.socket.removeListener('close', closeHandler);
  secureConnectResult.socket.removeListener('error', errorHandler);