Hi Jon,
NATS is basically a message queue, like ActiveMQ I suppose.
I included the adapter into the project using maven
<dependency>
<groupId>io.nats</groupId>
<artifactId>java-nats-streaming</artifactId>
<version>2.2.3</version>
</dependency>
i started up a nats server using docker. here is my docker-compose.yml
version: '3.1'
services:
nats-docker:
image: nats-streaming:0.17.0
restart: always
command:
- '-p'
- '4222'
- '-m'
- '8222'
- '-hbi'
- '5s'
- '-hbt'
- '5s'
- '-hbf'
- '2'
- '-SD'
- '-cid'
- 'yourclientid'
environment:
TZ: Europe/London
LANG: en_GB.UTF-8
LANGUAGE: en_GB:en
LC_ALL: en_GB.UTF-8
ports:
- '4222:4222'
- '8222:8222'
expose:
- 4222
- 8222
networks:
- backend
networks:
backend:
driver: bridge
JCA sounds good if it solves the threading issue. it is very kind of
you to offer to help write an adapter. looking at the code you sent it
looks complicated but i can have a stab at it if you don't have much time
let me know if you need more info
Matthew
On 07/06/2021 17:48, Jonathan Gallimore wrote:
At the risk of sounding a bit ignorant... what is NATS?
From what I can tell, it sounds like you're receiving a stream of events
(over websocket) and want to do some processing in an EJB or CDI bean for
each event. The connection to the NATS server isn't in the context of a
HTTP (or any other type of) request, and just runs all the time while the
server is running - does that sound about right?
Assuming that sounds right, it sounds a bit like the Slack JCA connector I
wrote a while back:
https://github.com/apache/tomee-chatterbox/tree/master/chatterbox-slack.
Essentially, the resource adapter connects to slack and runs all the time.
Messages that come into the server from slack are processed in MDBs that
implement the InboundListener interface.
JCA certainly feels complex, especially when compared with your
Singleton @Startup bean approach, but I usually find that if I try and work
with threads in EJBs, things usually go in the wrong direction. Conversely,
JCA even gives you a work manager to potentially handle that stuff.
If you can give me some pointers to running a NATS server, I'd be happy to
help with a sample adapter and application.
Jon
On Mon, Jun 7, 2021 at 11:49 AM Matthew Broadhead
<[email protected]> wrote:
I am trying to subscribe to a NATS streaming server with
https://github.com/nats-io/stan.java which is java.lang.Autocloseable.
At first it wasn't closing properly as seen in my original gist:
https://gist.github.com/chongma/2a3ab451f2aeabc98340a9b897394cfe
This was solved with this
https://stackoverflow.com/questions/39080296/hazelcast-threads-prevent-tomee-from-stopping
creating a default producer:
@ApplicationScoped
public class NatsConnectionProducer {
@Resource(name = "baseAddressNats")
private String baseAddressNats;
@Produces
@ApplicationScoped
public StreamingConnection instance() throws IOException,
InterruptedException {
StreamingConnectionFactory cf = new
StreamingConnectionFactory(new Options.Builder().natsUrl(baseAddressNats)
.clusterId("cluster-id").clientId("client-id").build());
return cf.createConnection();
}
public void destroy(@Disposes final StreamingConnection instance)
throws IOException, TimeoutException, InterruptedException {
instance.close();
}
}
But now i am creating a new thread because any injections with JPA had
cacheing issues and this seems to work but i am not sure it is
broadcasting to websockets correctly
@Singleton
@Lock(LockType.READ)
@Startup
public class SchedulerEvents {
private static final Logger log =
Logger.getLogger(SchedulerEvents.class.getName());
@Inject
private StreamingConnection streamingConnection;
@Inject
private SomeController someController;
@PostConstruct
private void construct() {
// log.fine(Thread.currentThread().getName());
try {
streamingConnection.subscribe("scheduler:notify", new
MessageHandler() {
@Override
public void onMessage(Message m) {
try {
log.fine(Thread.currentThread().getName());
// this needs to spawn a new thread otherwise
injections are stale
Thread thread = new Thread(new Runnable() {
public void run() {
log.fine(Thread.currentThread().getName());
process(m.getData());
}
});
thread.start();
while (thread.isAlive()) {
// wait
}
log.fine("Thread finished OK");
m.ack();
} catch (Exception e) {
emailController.emailStackTrace(e);
}
}
}, new
SubscriptionOptions.Builder().startWithLastReceived().manualAcks().ackWait(Duration.ofSeconds(60))
.durableName("scheduler-service").build());
} catch (IOException | InterruptedException | TimeoutException e)
{
e.printStackTrace();
}
}
private void process(byte[] data) {
String raw = new String(data);
JsonReader jsonReader = Json.createReader(new StringReader(raw));
JsonObject jo = jsonReader.readObject();
jsonReader.close();
String type = utilityDao.readJsonString(jo, "type");
int id = utilityDao.readJsonInteger(jo, "id");
if (type == null || id == 0) {
emailController.emailThrowable(new Throwable(), raw);
return;
}
log.info("Received a message: id: " + id + ", type:" + type);
DefaultServerEndpointConfigurator dsec = new
DefaultServerEndpointConfigurator();
SomeWebSocket nws = dsec.getEndpointInstance(SomeWebSocket.class);
nws.broadcast(ja.toString());
}
}
what is the best way to use an autocloseable?
