WebClient maxConnection pool limit?

Question

How many concurrent requests can I send if the remote service if blocking? Means: what is the maxConnection pool limit that spring uses internally when using WebClient?

@Autowired
private WebClient webClient;

webClient.post().uri(url).syncBody(req).retrieve().bodyToMono(type);

And moreover: how can I modify it?

Answer 1

Before reactor-netty 0.9.0.M4 version there wasn't limit by default because of "elastic" connection provider was used. This fix changed it to "fixed" connection provider with the limit of 500.

To change the connection pool limit you could define your own WebClient.Builder bean and use it to create WebClient

@Bean
public WebClient.Builder webClientBuilder() {
    String connectionProviderName = "myConnectionProvider";
    int maxConnections = 100;
    int acquireTimeout = 1000;
    HttpClient httpClient = HttpClient.create(ConnectionProvider
            .fixed(connectionProviderName, maxConnections, acquireTimeout));
    return WebClient.builder()
            .clientConnector(new ReactorClientHttpConnector(httpClient));
}

Or you could implement custom org.springframework.boot.web.reactive.function.client.WebClientCustomizer in the same manner with the predefined WebClient.Builder

Answer 2

taken from the netty documentation

By default, the TCP client uses a “fixed” connection pool with 500 as the maximum number of the channels and 45s as the acquisition timeout.