The basic problem is that when we are streaming in updates via a client, an update can fail in a way that further updates in the request will not be processed, but not in a way that causes the client to stop and finish up the request before the server does something else with that connection.
This seems to mean that even after the server stops processing the request, the concurrent update client is still in the process of sending the request. It seems previously, Jetty would not go after the connection very quickly after the server processing thread was stopped via exception, and the client (usually?) had time to clean up properly. But after the Jetty upgrade from 9.2 to 9.3, Jetty closes the connection on the server sooner than previous versions , and the client does not end up getting notified of the original exception at all and instead hits a connection reset exception. The result was random fails due to connection reset throughout our tests and one particular test failing consistently. Even before this update, it does not seem like we are acting in a safe or 'behaved' manner, but our version of Jetty was relaxed enough (or a bug was fixed?) for our tests to work out.