final Map<String, Object> map = new LinkedHashMap<>();
        map.put("type", "heartbeat");
        map.put("instanceId", "test-instance");
        map.put("createdTime", 1000L);

        final String json = coordinatorHelper.toJson(map);
        assertNotNull(json);
        assertTrue(json.contains("\"type\":\"heartbeat\""));
        assertTrue(json.contains("\"instanceId\":\"test-instance\""));

                logger.warn("Failed to send heartbeat: status={}", response.getHttpStatusCode());
            }
        } catch (final Exception e) {
            logger.debug("Failed to send heartbeat.", e);
        }
    }

    /**
     * Removes the heartbeat document for this instance from OpenSearch.
     */
    protected void removeHeartbeat() {

#                                                Coordinator
#                                                     ------

# Interval (seconds) for polling heartbeats and events.
coordinator.poll.interval=60
# Time-to-live (ms) for instance heartbeat documents.
coordinator.heartbeat.ttl=180000
# Time-to-live (ms) for operation lock documents.
coordinator.operation.ttl=7200000
# Maximum number of retries for acquiring an operation lock.

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getCoordinatorHeartbeatTtl();

    /**
     * Get the value for the key 'coordinator.heartbeat.ttl' as {@link Integer}. <br>
     * The value is, e.g. 180000 <br>
     * comment: Time-to-live (ms) for instance heartbeat documents.

- The kubelet no longer forcefully closes active connections on heartbeat failures, using the HTTP2 health check mechanism to detect broken connections. Users can force the previous behavior of the kubelet by setting the environment variable DISABLE_HTTP2. ([#108107](https://github.com/kubernetes/kubernetes/pull/108107),...