Configuring Spring WebFlux WebClient to use a custom thread pool - spring-boot

Question

Is it possible to configure WebClient to use a custom thread pool other than the reactor-http-nio thread pool (When using Netty)? If it is possible , can we somehow restrict that custom thread pool to run only on a particular processor core?

Answer 1

Yes. You can.
Create some where your own Thread Pool and EventLoopGroup (or create NioEventLoopGroup bean). For example:
{
Intger THREADS = 10;
BasicThreadFactory THREADFACTORY = new BasicThreadFactory.Builder()
.namingPattern("HttpThread-%d")
.daemon(true)
.priority(Thread.MAX_PRIORITY)
.build();
EXECUTOR = new ThreadPoolExecutor(
THREADS,
THREADS,
0L,
TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(),
THREADFACTORY,
new ThreadPoolExecutor.AbortPolicy());
NioEventLoopGroup RESOURCE= new NioEventLoopGroup(THREADS,EXECUTOR);
}
Register your own ReactorResourceFactory. And provide your own EventLoopGrooup based on custom thread Executor
#Bean
public ReactorResourceFactory reactorResourceFactory(NioEventLoopGroup RESOURCE) {
ReactorResourceFactory f= new ReactorResourceFactory();
f.setLoopResources(new LoopResources() {
#Override
public EventLoopGroup onServer(boolean b) {
return RESOURCE;
}
});
f.setUseGlobalResources(false);
return f;
}
Then register ReactorClientHttpConnector. In example below it is used custom SSL Context
#Bean
public ReactorClientHttpConnector reactorClientHttpConnector(ReactorResourceFactory r) throws SSLException {
SslContext sslContext = SslContextBuilder
.forClient()
.trustManager(InsecureTrustManagerFactory.INSTANCE)
.build();
return new ReactorClientHttpConnector(r, m -> m.secure(t -> t.sslContext(sslContext)));
}
Finally build WebClient
#Bean
public WebClient webClient(ReactorClientHttpConnector r) {
return WebClient.builder().clientConnector(r).build();
}
If you want to use same for WebServer. Do same configuration for ReactiveWebServerFactory.
#Bean
public ReactiveWebServerFactory reactiveWebServerFactory(NioEventLoopGroup RESOURCE) {
NettyReactiveWebServerFactory factory = new NettyReactiveWebServerFactory();
factory.addServerCustomizers(hs->hs.tcpConfiguration(s->s.runOn(RESOURCE)));
return factory;
}
Imports:
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.DependsOn;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.http.client.reactive.ReactorResourceFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.netty.resources.LoopResources;
import org.apache.commons.lang3.concurrent.BasicThreadFactory;
import org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory;
import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
import java.util.concurrent.*;