WebClient|RestTemplate|WireMock : Mixing async httpClient create some blocking process

[alexisgayte]

While I am not sure this bug is directly linked to spring framework.

If you use the test framework with WebTestClient and restTemplate connecting to a mockServer. It creates a blocking process at the restTemplate level.

I first wanted to check if you guys were aware of this issue?

It seems to be linked to the mock server as well. As hitting an external server directly will work.

So WebClient(async) used in the test + RestTemplate in the app + MockServer --> return a concurrent issue.
So RestTemplate used in the test + RestTemplate in the app + MockServer --> works fine
So WebClient(async) used in the test + RestTemplate in the app + Direct server --> work fine

@RestController
@RequestMapping("/test")
@Slf4j
public class TestController {

    RestTemplate restTemplate;

    TestController() {
        restTemplate = new RestTemplateBuilder()
                .build();
    }

    @PostMapping(consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<TestResponse> postTransaction(@Valid @RequestBody TestRequest testRequest,
                                                               @RequestHeader HttpHeaders headers) {
        
        HttpEntity<testRequest> entity = new HttpEntity<>(testRequest, headers);
        restTemplate.postForObject("http://localhost:6666/myTest", entity, TestResponse.class);

        return null;
    }

}

@ActiveProfiles("integration-test")
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureMockMvc
@AutoConfigureWireMock(files = "file:./happy-path", port = 6666)
public class TestControllerIT {
    @Autowired
    private WebTestClient client;
    
    @Test
    public void testWithWebClient() throws Exception {

        client.post().uri("/test")
                .bodyValue(testRequest)
                .header("Content-Type", "application/json")
                .exchange()
                .expectStatus().isEqualTo(200)
                .expectBody();

    }
}

Same test using RestTemplate will work fine.

@ActiveProfiles("integration-test")
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureMockMvc
@AutoConfigureWireMock(files = "file:./happy-path", port = 6666)
public class TestControllerIT {

    @LocalServerPort
    private int port;

    @Autowired
    private TestRestTemplate testRestTemplate;

    @Test
    public void testWithRestTemplate() throws Exception {
        
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        ResponseEntity<String> entity = testRestTemplate.exchange("http://localhost:" + port + "/test",
                HttpMethod.POST,
                new HttpEntity<>(testRequest, headers),
                String.class);

        assertEquals(HttpStatusCode.valueOf(200), entity.getStatusCode());
    }
}

The error generated is :

10:24:54.004 [Test worker] WARN  i.o.t.c.ExceptionAdviceHandler - Generic exception thrown: 500 Server Error: "{<EOL>"cause2":"java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"cause1":"java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"servlet":"com.github.tomakehurst.wiremock.servlet.WireMockHandlerDispatchingServlet-3b84359c",<EOL>"cause0":"java.lang.RuntimeException: java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"message":"java.lang.RuntimeException: java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"url":"/test",<EOL>"status":"500"<EOL>}"
org.springframework.web.client.HttpServerErrorException$InternalServerError: 500 Server Error: "{<EOL>"cause2":"java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"cause1":"java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"servlet":"com.github.tomakehurst.wiremock.servlet.WireMockHandlerDispatchingServlet-3b84359c",<EOL>"cause0":"java.lang.RuntimeException: java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"message":"java.lang.RuntimeException: java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 30004/30000 ms",<EOL>"url":"/test",<EOL>"status":"500"<EOL>}"
	at org.springframework.web.client.HttpServerErrorException.create(HttpServerErrorException.java:102)
	at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:186)
	at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:137)
	at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63)
	at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:942)
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:891)
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:790)
	at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:507)
	at xxxTestController.postTransaction(TestController.java:64)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:255)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:188)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:926)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:831)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914)
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:547)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885)
	at org.springframework.test.web.servlet.TestDispatcherServlet.service(TestDispatcherServlet.java:72)
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:614)
	at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:165)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:151)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:151)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:151)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.web.filter.ServerHttpObservationFilter.doFilterInternal(ServerHttpObservationFilter.java:113)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:151)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:151)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
	at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:201)
	at org.springframework.test.web.servlet.client.MockMvcHttpConnector.connect(MockMvcHttpConnector.java:106)
	at org.springframework.test.web.reactive.server.WiretapConnector.connect(WiretapConnector.java:71)
	at org.springframework.web.reactive.function.client.ExchangeFunctions$DefaultExchangeFunction.exchange(ExchangeFunctions.java:102)
	at org.springframework.test.web.reactive.server.DefaultWebTestClient$DefaultRequestBodyUriSpec.exchange(DefaultWebTestClient.java:359)

[bclozel]

@alexisgayte did you close this by mistake? Did you find where the issue came from?

[alexisgayte]

I did close it and I didn't find the issue yet.
But I couldn't reproduce it in isolation with a clean gradle import.

It seems more complex than just this simple code probably link to lib interaction. I wasn't really sure this is linked to spring and I didn't want to bother you. I will open a new one if I have more evidence.

[bclozel]

Please share your sample project as a zip. That should help us to reproduce the problem.

[alexisgayte]

Is that enough?