@Override
        public void onConnectorConfigUpdate(String connector) {
            log.info("Connector {} config updated", connector);

            // Stage the update and wake up the work thread. Connector config *changes* only need the one connector
            // to be bounced. However, this callback may also indicate a connector *addition*, which does require
            // a rebalance, so we need to be careful about what operation we request.
            synchronized (DistributedHerder.this) {
                if (!configState.contains(connector)) {
                    needsReconfigRebalance = true;
                } else {
                    // Only need to restart the connector if it already existed
                    connectorConfigUpdates.add(connector);
                }

            }
            member.wakeup();
        }
Execute the given action and subsequent callback immediately if the current thread is the herder's tick thread,
or use them to create and store a {@link DistributedHerderRequest} on the request queue and return the resulting request
if not.
@param action the action that should be run on the herder's tick thread
@param callback the callback that should be invoked once the action is complete
@return a new {@link DistributedHerderRequest} if one has been created and added to the request queue, and {@code null} otherwise
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java