Merge pull request kubernetes#89881 from embano1/etcd-leader-ctx

Add etcd WithRequireLeader option to API watches

Author: k8s-ci-robot

staging/src/k8s.io/apiserver/pkg/storage/etcd3/watcher.go

@@ -126,7 +126,15 @@ func (w *watcher) createWatchChan(ctx context.Context, key string, rev int64, re
 		// The filter doesn't filter out any object.
 		wc.internalPred = storage.Everything
 	}
-	wc.ctx, wc.cancel = context.WithCancel(ctx)
+
+	// The etcd server waits until it cannot find a leader for 3 election
+	// timeouts to cancel existing streams. 3 is currently a hard coded
+	// constant. The election timeout defaults to 1000ms. If the cluster is
+	// healthy, when the leader is stopped, the leadership transfer should be
+	// smooth. (leader transfers its leadership before stopping). If leader is
+	// hard killed, other servers will take an election timeout to realize
+	// leader lost and start campaign.
+	wc.ctx, wc.cancel = context.WithCancel(clientv3.WithRequireLeader(ctx))
 	return wc
 }