@Override
        public void run() {
            log.info("Starting");

            try {
                handleEvents();
            } catch (Throwable t) {
                log.error("Exiting with exception.", t);
            }

            // The accumulator is drained and all the pending events are rejected
            // when the event processor is shutdown.
            if (shuttingDown) {
                log.info("Shutting down. Draining the remaining events.");
                try {
                    drainEvents();
                } catch (Throwable t) {
                    log.error("Draining threw exception.", t);
                }
                log.info("Shutdown completed");
            }
        }
The event processor thread. The thread pulls events from the
accumulator and runs them.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/runtime/MultiThreadedEventProcessor.java