@Override
        public TreeMap<Long, WorkerState> call() throws Exception {
            TreeMap<Long, WorkerState> workerMap = new TreeMap<>();
            for (Worker worker : workers.values()) {
                workerMap.put(worker.workerId(), worker.state());
            }
            return workerMap;
        }
Cleans up the resources associated with a worker.  Processed by the worker
cleanup thread pool.
trogdor/src/main/java/org/apache/kafka/trogdor/agent/WorkerManager.java