DefaultEurekaClientHttpRequestFactorySupplier HttpClient is not closed

[Ive4]

Describe the bug
spring cloud 2021.0.0
Eureka Client has a bug, the bug is that every time the heartbeat and request Eureka Server will create a new HttpClient, but this new HttpClient will not be manually closed, only when the FullGC will be cleaned up, so it leads to the problem of too much TCP CLOSE_WAIT.

Sample
The solution is to provide a shared HttpClient, rather than re-creating a new one for each request.

[OlgaMaciaszek]

Hello, @Ive4 thanks for submitting this. I'm not sure what you mean. In the CloudEurekaClient that handles publishing the HeartbeatEvent, this method is called that should reuse an existing EurekaHttpClient. Could you please point me to the code you have in mind or provide a minimal, complete, verifiable example that reproduces the issue along with the steps to reproduce?

[Ive4]

Sorry, I didn't make it clear.
Eureka publishing HeartbeatEvent will invoke RedirectingEurekaHttpClient.execute.
EurekaClient will shutdown when an exception occurs on an http request, but not shutdown HttpClient

[OlgaMaciaszek]

Hello, @Ive4 if I understand correctly, the issue concerns the RedirectingEurekaHttpClient itself rather than its Spring integration provided by Spring Cloud? If so, please create an issue in the Eureka repo instead.

[spring-cloud-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

[spring-cloud-issues]

Closing due to lack of requested feedback. If you would like us to look at this issue, please provide the requested information and we will re-open the issue.

[BenEfrati]

Hi @OlgaMaciaszek ,
@Ive4 is right

EurekaClient will shutdown when an exception occurs on an http request, but not shutdown HttpClient

This bug is related to

spring-cloud-netflix/spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/http/RestTemplateEurekaHttpClient.java

Line 203 in 27ac337

// Nothing to do

In case of exception here:
https://github.com/Netflix/eureka/blob/ed0da19ca1c049c87e3dbf75b6015c1861d5c2d0/eureka-client/src/main/java/com/netflix/discovery/shared/transport/decorator/RedirectingEurekaHttpClient.java#L96
new HttpClient will be created without closing the existing one - this causes CLOSE_WAIT connections

I'll try to explain the issue, let me know if you still want complete mvce.
This supplier creates new CloseableHttpClient for every call to

spring-cloud-netflix/spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/http/RestTemplateTransportClientFactory.java

Line 103 in 27ac337

public EurekaHttpClient newClient(EurekaEndpoint serviceUrl) {

public class DefaultEurekaClientHttpRequestFactorySupplier implements EurekaClientHttpRequestFactorySupplier {

	@Override
	public ClientHttpRequestFactory get(SSLContext sslContext, @Nullable HostnameVerifier hostnameVerifier) {
		HttpClientBuilder httpClientBuilder = HttpClients.custom();
		if (sslContext != null) {
			httpClientBuilder = httpClientBuilder.setSSLContext(sslContext);
		}
		if (hostnameVerifier != null) {
			httpClientBuilder = httpClientBuilder.setSSLHostnameVerifier(hostnameVerifier);
		}
		CloseableHttpClient httpClient = httpClientBuilder.build();
		HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();
		requestFactory.setHttpClient(httpClient);
		return requestFactory;
	}

}

so in case of shutdown, currentEurekaClient shutdown don't closes connections:

spring-cloud-netflix/spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/http/RestTemplateEurekaHttpClient.java

Line 203 in 27ac337

// Nothing to do

as @Ive4 said, only Full GC closes the opened connections.

possible solution will be trying to close the HttpClient:
shutdown could be

public void shutdown() {
        Optional.of(unwrapRequestFactoryIfNecessary(restTemplate.getRequestFactory()))
                .filter(HttpComponentsClientHttpRequestFactory.class::isInstance)
                .map(HttpComponentsClientHttpRequestFactory.class::cast)
                .ifPresent(requestFactory-> {
                    try {
                        requestFactory.destroy();
                    } catch (Exception e) {
                    }
                });
    }

unwrapRequestFactoryIfNecessary
https://github.com/spring-projects/spring-boot/blob/47516b50c39bd6ea924a1f6720ce6d4a71088651/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/client/RestTemplateBuilder.java#L746

spring-projects/spring-boot#31075