Workaround for the slowness of the WebClient first request - spring-boot

Question

I am using WebClient in a Spring Boot MVC 2.1 project and found that the first request made by the client takes up to 6 seconds. Subsequent requests are way faster (~30ms).
There's a closed issue in Spring's JIRA that advices using Jetty as the WebClient Http connector. I have tried that approach, improving the figures, with a ~800ms first request. This time is an improvement but it's still far from RestTemplate which usally takes <200ms.
Netty approach (5s first request):
Conf:
#Bean
public WebClient webClient() {
return WebClient.create();
}
Usage:
private final WebClient webClient;
#GetMapping(value="/wc", produces = APPLICATION_JSON_UTF8_VALUE)
public Mono<String> findWc() throws URISyntaxException {
URI uri = new URI("http://xxx");
final Mono<String> response = webClient.get().uri(uri).retrieve().bodyToMono(String.class);
return response;
}
Jetty approach (800ms first request):
Conf:
#Bean
public JettyResourceFactory resourceFactory() {
return new JettyResourceFactory();
}
#Bean
public WebClient webClient() {
ClientHttpConnector connector = new JettyClientHttpConnector(resourceFactory(), null);
return WebClient.builder().clientConnector(connector).build();
}
Usage: same as before.
There's another "problem" with the Jetty approach. On server shutdown it always produces the following exception:
27-Dec-2018 11:24:20.463 INFO [jetty-http#74305db9-65] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [org.eclipse.jetty.io.ManagedSelector$StopSelector]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [org.eclipse.jetty.io.ManagedSelector$StopSelector]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1348)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1336)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1195)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
at java.lang.Class.getDeclaringClass0(Native Method)
at java.lang.Class.getDeclaringClass(Class.java:1235)
at java.lang.Class.getEnclosingClass(Class.java:1277)
at java.lang.Class.getSimpleBinaryName(Class.java:1443)
at java.lang.Class.getSimpleName(Class.java:1309)
at org.eclipse.jetty.io.ManagedSelector$SelectorProducer.toString(ManagedSelector.java:534)
at java.lang.String.valueOf(String.java:2994)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.getString(EatWhatYouKill.java:458)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.toStringLocked(EatWhatYouKill.java:447)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.toString(EatWhatYouKill.java:440)
at org.slf4j.helpers.MessageFormatter.safeObjectAppend(MessageFormatter.java:299)
at org.slf4j.helpers.MessageFormatter.deeplyAppendParameter(MessageFormatter.java:271)
at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:233)
at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:173)
at org.eclipse.jetty.util.log.JettyAwareLogger.log(JettyAwareLogger.java:680)
at org.eclipse.jetty.util.log.JettyAwareLogger.debug(JettyAwareLogger.java:224)
at org.eclipse.jetty.util.log.Slf4jLog.debug(Slf4jLog.java:97)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:288)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
at java.lang.Thread.run(Thread.java:748)
SLF4J: Failed toString() invocation on an object of type [org.eclipse.jetty.util.thread.strategy.EatWhatYouKill]
Reported exception:
java.lang.NoClassDefFoundError: org/eclipse/jetty/io/ManagedSelector$StopSelector
at java.lang.Class.getDeclaringClass0(Native Method)
at java.lang.Class.getDeclaringClass(Class.java:1235)
at java.lang.Class.getEnclosingClass(Class.java:1277)
at java.lang.Class.getSimpleBinaryName(Class.java:1443)
at java.lang.Class.getSimpleName(Class.java:1309)
at org.eclipse.jetty.io.ManagedSelector$SelectorProducer.toString(ManagedSelector.java:534)
at java.lang.String.valueOf(String.java:2994)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.getString(EatWhatYouKill.java:458)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.toStringLocked(EatWhatYouKill.java:447)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.toString(EatWhatYouKill.java:440)
at org.slf4j.helpers.MessageFormatter.safeObjectAppend(MessageFormatter.java:299)
at org.slf4j.helpers.MessageFormatter.deeplyAppendParameter(MessageFormatter.java:271)
at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:233)
at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:173)
at org.eclipse.jetty.util.log.JettyAwareLogger.log(JettyAwareLogger.java:680)
at org.eclipse.jetty.util.log.JettyAwareLogger.debug(JettyAwareLogger.java:224)
at org.eclipse.jetty.util.log.Slf4jLog.debug(Slf4jLog.java:97)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:288)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: Illegal access: this web application instance has been stopped already. Could not load [org.eclipse.jetty.io.ManagedSelector$StopSelector]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1338)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1195)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
... 25 more
Caused by: java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [org.eclipse.jetty.io.ManagedSelector$StopSelector]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1348)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1336)
... 27 more
27-Dec-2018 11:24:20.467 INFO [jetty-http#74305db9-65] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [ch.qos.logback.classic.spi.ThrowableProxy]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [ch.qos.logback.classic.spi.ThrowableProxy]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1348)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1336)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1195)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
at ch.qos.logback.classic.spi.LoggingEvent.<init>(LoggingEvent.java:119)
at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:419)
at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:383)
at ch.qos.logback.classic.Logger.log(Logger.java:765)
at org.eclipse.jetty.util.log.JettyAwareLogger.log(JettyAwareLogger.java:668)
at org.eclipse.jetty.util.log.JettyAwareLogger.warn(JettyAwareLogger.java:474)
at org.eclipse.jetty.util.log.Slf4jLog.warn(Slf4jLog.java:73)
at org.eclipse.jetty.util.log.Slf4jLog.warn(Slf4jLog.java:67)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.execute(EatWhatYouKill.java:375)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:305)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
at java.lang.Thread.run(Thread.java:748)
Exception in thread "jetty-http#74305db9-65" java.lang.NoClassDefFoundError: ch/qos/logback/classic/spi/ThrowableProxy
at ch.qos.logback.classic.spi.LoggingEvent.<init>(LoggingEvent.java:119)
at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:419)
at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:383)
at ch.qos.logback.classic.Logger.log(Logger.java:765)
at org.eclipse.jetty.util.log.JettyAwareLogger.log(JettyAwareLogger.java:668)
at org.eclipse.jetty.util.log.JettyAwareLogger.warn(JettyAwareLogger.java:474)
at org.eclipse.jetty.util.log.Slf4jLog.warn(Slf4jLog.java:73)
at org.eclipse.jetty.util.log.Slf4jLog.warn(Slf4jLog.java:67)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:740)
at java.lang.Thread.run(Thread.java:748)
How can I avoid this exception?
Is there any other way we can use to improve the WebClient first request slowness?

Answer 1

I went through the same problem and managed to solve it by changing the connector used by the WebClient.
Below the configuration file with the appropriate imports
import org.eclipse.jetty.client.HttpClient;
import org.eclipse.jetty.util.ssl.SslContextFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.reactive.ClientHttpConnector;
import org.springframework.http.client.reactive.JettyClientHttpConnector;
import org.springframework.web.reactive.function.client.WebClient;
The class
SslContextFactory.Client sslContextFactory = new SslContextFactory.Client();
HttpClient httpClient = new HttpClient(sslContextFactory);
httpClient.setFollowRedirects(false);
httpClient.setConnectTimeout(TIMEOUT);
httpClient.start();
final ClientHttpConnector connector = new JettyClientHttpConnector(httpClient);
final WebClient webClient = WebClient.builder()
.clientConnector(connector)
.baseUrl(BASE_URL)
.build();
It is important to know how to add the right libs to your project, so below is how I managed to import using gradle:
implementation 'org.eclipse.jetty:jetty-client'
implementation 'org.eclipse.jetty:jetty-reactive-httpclient'

Answer 2

We upgraded Spring Boot to 2.4.2 with reactor-netty 1.0.3 but still encounter this issue.
Here is our upgraded configuration:
#Bean
public WebClient createWebClient(WebClient.Builder webClientBuilder) {
log.info("Initializing WebClient Bean");
final int timeoutInMillis = Long.valueOf(TimeUnit.SECONDS.toMillis(timeout)).intValue();
final HttpClient httpClient = HttpClient.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, timeoutInMillis)
.responseTimeout(Duration.ofMillis(timeoutInMillis))
.doOnConnected(conn ->
conn.addHandlerLast(new ReadTimeoutHandler(timeoutInMillis, TimeUnit.MILLISECONDS))
.addHandlerLast(new WriteTimeoutHandler(timeoutInMillis, TimeUnit.MILLISECONDS)));
final ClientHttpConnector connector = new ReactorClientHttpConnector(httpClient);
final WebClient webClient = webClientBuilder
.clientConnector(connector)
.defaultHeader("x-clientname", clientname)
.build();
httpClient.warmup().block();
log.info("WebClient initialized");
return webClient;
}
Our call with WebClient:
ResoponseObject doCall() {
return this.webClient
.get()
.uri("http://***.de/api/rest/***")
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.bodyToMono(ResponseObject.class)
.block();
}
With debugging enabled via application.yaml:
logging.level.reactor.netty: debug
We now see this during application startup:
2021-02-10 17:02:31,922 INFO d.t.e.b.c.c.WebClientAutoConfiguration - Initializing WebClient Bean
2021-02-10 17:02:31,959 DEBUG r.n.r.DefaultLoopIOUring - Default io_uring support : false
2021-02-10 17:02:31,967 DEBUG r.n.r.DefaultLoopEpoll - Default Epoll support : true
2021-02-10 17:02:31,997 INFO d.t.e.b.c.c.WebClientAutoConfiguration - WebClient initialized
This should be an indication that the warmup works as expected?
But on first request this happens:
2021-02-10 17:05:16,045 DEBUG o.s.w.r.f.c.ExchangeFunctions - [73d400c8] HTTP GET http://***.de/api/rest/***
2021-02-10 17:05:16,050 DEBUG r.n.r.PooledConnectionProvider - Creating a new [http] client pool [PoolFactory{evictionInterval=PT0S, leasingStrategy=fifo, maxConnections=500, maxIdleTime=-1, maxLifeTime=-1, metricsEnabled=false, pendingAcquireMaxCount=1000, pendingAcquireTimeout=45000}] for [***.de/<unresolved>:80]
2021-02-10 17:05:29,619 DEBUG r.n.r.DefaultPooledConnectionProvider - [id: 0x71b840f4] Created a new pooled channel, now 1 active connections and 0 inactive connections
2021-02-10 17:05:29,635 DEBUG r.n.t.TransportConfig - [id: 0x71b840f4] Initialized pipeline DefaultChannelPipeline{(reactor.left.httpCodec = io.netty.handler.codec.http.HttpClientCodec), (reactor.right.reactiveBridge = reactor.netty.channel.ChannelOperationsHandler)}
...
In our case, creating the client pool is the problem. On a decent machine, it takes about 13 seconds.
Can you give us any comment on that? This is very this is very frustrating for us.
Thanks a lot!