TreeSet<String> findNodeNames() {
            Set<String> nodeNames = controller.targetNodes(platform.topology());
            TreeSet<String> validNodeNames = new TreeSet<>();
            TreeSet<String> nonExistentNodeNames = new TreeSet<>();
            for (String nodeName : nodeNames) {
                if (nodeManagers.containsKey(nodeName)) {
                    validNodeNames.add(nodeName);
                } else {
                    nonExistentNodeNames.add(nodeName);
                }
            }
            if (!nonExistentNodeNames.isEmpty()) {
                throw new KafkaException("Unknown node names: " +
                        String.join(", ", nonExistentNodeNames));
            }
            if (validNodeNames.isEmpty()) {
                throw new KafkaException("No node names specified.");
            }
            return validNodeNames;
        }
If this is non-empty, a message describing how this task failed.
trogdor/src/main/java/org/apache/kafka/trogdor/coordinator/TaskManager.java