Spring Boot Undertow add RequestLimitingHandler to DeploymentInfo

Question

I am using Spring Boot with Undertow and trying to implement some limits on the number of requests Undertow will accept so as not to become overloaded under stress.

I've seen the answer to the question at Spring Boot Undertow add both blocking handler and NIO handler in the same application, and it appears promising, but I'm not clear what HttpHandler should be passed as the argument to the RequestLimitingHandler constructor.

Is there an easy way to add a RequestLimitingHandler to the UndertowEmbeddedServletContainerFactory bean, perhaps using the addDeploymentInfoCustomizers method?

Alternatively, if I look deeper and get into the Xnio code on which Undertow is based, it looks like there is an option to set Options.WORKER_TASK_LIMIT, but upon further investigation, it looks like the XnioWorker class ignores this setting after the 3.0.10.GA release and simply sets taskQueue to an unbounded LinkedBlockingQueue. Am I mistaken and could this also be an option?

Answer 1

Answering my own question in case it helps others in the future. Solution is to create a new Undertow HandlerWrapper and instantiate the new RequestLimitingHandler object within the wrap() method, like so:

@Bean
public UndertowEmbeddedServletContainerFactory embeddedServletContainerFactory(RootHandler rootHandler) {
    UndertowEmbeddedServletContainerFactory factory = new UndertowEmbeddedServletContainerFactory();

    factory.addDeploymentInfoCustomizers(deploymentInfo -> deploymentInfo.addInitialHandlerChainWrapper(new HandlerWrapper() {

        @Override
        public HttpHandler wrap(HttpHandler handler) {
            return new RequestLimitingHandler(maxConcurrentRequests, queueSize, handler);
        }

    }));

    return factory;
}