private JsonNode getCombinedStatus() {
            if (workerIds.size() == 1) {
                return workerStates.get(workerIds.values().iterator().next()).status();
            } else {
                ObjectNode objectNode = new ObjectNode(JsonNodeFactory.instance);
                for (Map.Entry<String, Long> entry : workerIds.entrySet()) {
                    String nodeName = entry.getKey();
                    Long workerId = entry.getValue();
                    WorkerState state = workerStates.get(workerId);
                    JsonNode node = state.status();
                    if (node != null) {
                        objectNode.set(nodeName, node);
                    }
                }
                return objectNode;
            }
        }
If this is non-empty, a message describing how this task failed.
trogdor/src/main/java/org/apache/kafka/trogdor/coordinator/TaskManager.java