### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
server/src/main/java/org/elasticsearch/transport/TransportService.java
return e instanceof RemoteTransportException remoteTransportException
                ? remoteTransportException
                : new RemoteTransportException(localNode.getName(), localNode.getAddress(), action, e);
        }
        protected void processException(final TransportResponseHandler<?> handler, final RemoteTransportException rtx) {
            try {
                handler.handleException(rtx);
            } catch (Exception e) {
                logger.error(() -> format("failed to handle exception for action [%s], handler [%s]", action, handler), e);
            }
        }
        @Override
        public String getChannelType() {
            return "direct";
        }
        @Override
        public Version getVersion() {
            return localNode.getVersion();
        }
    }
    /**
     * Returns the internal thread pool
     */
    public ThreadPool getThreadPool() {
        return threadPool;
    }
    private boolean isLocalNode(DiscoveryNode discoveryNode) {
        return Objects.requireNonNull(discoveryNode, "discovery node must not be null").equals(localNode);
    }
    private static final class DelegatingTransportMessageListener implements TransportMessageListener {