如何在 reactor.netty 服务器的 Spring Webflux 中监控仪表

Question

I am new to Spring Boot and Spring Webflux. I am working on a Spring Webflux reactor.netty server to handle WebSocket connections. In the simplest sense, this is how the server looks like:

...
@Component
public class ServerWebSocketHandler implements WebSocketHandler {

    private final Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public Mono<Void> handle(WebSocketSession session) {
        String sessionId = session.getId();
        Sinks.Many<String> unicastSink = Sinks.many().unicast().onBackpressureError();
        // save the unicastSink in cache so that on demand messages can be sent to the sink
        Mono<Void> receiver =
                session
                    .receive()
                    .map(WebSocketMessage::getPayloadAsText)
                    .doOnNext(message -> this.handleIncomingMessage(sessionId, message))
                    .doOnError(error -> {
                        logger.info("Error occurred in the session - Session: '{}'; Error: '{}'", sessionId, error);
                    })
                    .doFinally(s -> {
                        this.cleanUp(sessionId, s);
                    })
                    .then();

        Mono<Void> sender =
                session
                    .send(unicastSink.asFlux().map(session::textMessage));

        return Mono.zip(receiver, sender).then();
    }
    // handleIncomingMessage, cleanUp, and other private methods to handle business logic
}

Now, I want to monitor the meters, specifically meters that can help in identifying back pressure or memory leak like reactor.netty.eventloop.pending.tasks , reactor.netty.bytebuf.allocator.used.direct.memory , reactor.netty.bytebuf.allocator.used.heap.memory . I read about these meters in Reactor Netty Reference Guide https://projectreactor.io/docs.netty/1.1.0-SNAPSHOT/reference/index.html#_metrics . The example of how to enable it is done on the server creation, but in Webflux, all these are abstracted out. So, my question is, in this case, how can I enable monitoring the meters and how to consume the meter. A small example code which shows how to do it would be greatly useful.

Answer 1

You can use Spring Boot API for configuring the web server https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto.webserver.configure

@Component
public class MyNettyWebServerCustomizer
        implements WebServerFactoryCustomizer<NettyReactiveWebServerFactory> {
    @Override
    public void customize(NettyReactiveWebServerFactory factory) {
        factory.addServerCustomizers(httpServer -> httpServer.metrics(...));
    }
}

These built-in Reactor Netty metrics use Micrometer so you can consume them with everything that has integration with Micrometer.