Introduce skipForcedClientInitialization property.

Fixes spring-cloudgh-4152

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

@@ -269,6 +269,12 @@ public class EurekaInstanceConfigBean implements CloudEurekaInstanceConfig, Envi
 	 */
 	private boolean preferIpAddress = false;
 
+	/**
+	 * If true the EurekaClient will not be forced to initialize when the InstanceRegistry
+	 * bean is created.
+	 */
+	private boolean skipForcedClientInitialization;
+
 	/**
 	 * Initial status to register with remote Eureka server.
 	 */
@@ -547,6 +553,14 @@ public void setPreferIpAddress(boolean preferIpAddress) {
 		this.preferIpAddress = preferIpAddress;
 	}
 
+	public boolean isSkipForcedClientInitialization() {
+		return skipForcedClientInitialization;
+	}
+
+	public void setSkipForcedClientInitialization(boolean skipForcedClientInitialization) {
+		this.skipForcedClientInitialization = skipForcedClientInitialization;
+	}
+
 	public InstanceStatus getInitialStatus() {
 		return initialStatus;
 	}
@@ -597,6 +611,7 @@ public boolean equals(Object o) {
 				&& Objects.equals(namespace, that.namespace) && Objects.equals(hostname, that.hostname)
 				&& preferIpAddress == that.preferIpAddress && Objects.equals(initialStatus, that.initialStatus)
 				&& Arrays.equals(defaultAddressResolutionOrder, that.defaultAddressResolutionOrder)
+				&& skipForcedClientInitialization == that.skipForcedClientInitialization
 				&& Objects.equals(environment, that.environment);
 	}
 
@@ -607,7 +622,7 @@ public int hashCode() {
 				leaseExpirationDurationInSeconds, virtualHostName, instanceId, secureVirtualHostName, aSGName,
 				metadataMap, dataCenterInfo, ipAddress, statusPageUrlPath, statusPageUrl, homePageUrlPath, homePageUrl,
 				healthCheckUrlPath, healthCheckUrl, secureHealthCheckUrl, namespace, hostname, preferIpAddress,
-				initialStatus, Arrays.hashCode(defaultAddressResolutionOrder), environment);
+				skipForcedClientInitialization, initialStatus, Arrays.hashCode(defaultAddressResolutionOrder), environment);
 	}
 
 	@Override
@@ -631,6 +646,7 @@ public String toString() {
 				.append("', ").append("healthCheckUrl='").append(healthCheckUrl).append("', ")
 				.append("secureHealthCheckUrl='").append(secureHealthCheckUrl).append("', ").append("namespace='")
 				.append(namespace).append("', ").append("hostname='").append(hostname).append("', ")
+				.append("skipForcedClientInitialization=").append(skipForcedClientInitialization).append(", ")
 				.append("preferIpAddress=").append(preferIpAddress).append(", ").append("initialStatus=")
 				.append(initialStatus).append(", ").append("defaultAddressResolutionOrder=")
 				.append(Arrays.toString(defaultAddressResolutionOrder)).append(", ").append("environment=")

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/EurekaServerAutoConfiguration.java

@@ -86,6 +86,7 @@
 import org.springframework.cloud.client.actuator.HasFeatures;
 import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
 import org.springframework.cloud.netflix.eureka.EurekaConstants;
+import org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
@@ -198,9 +199,16 @@ public Jersey3EurekaServerHttpClientFactory jersey3EurekaServerHttpClientFactory
 
 	@Bean
 	public PeerAwareInstanceRegistry peerAwareInstanceRegistry(ServerCodecs serverCodecs,
-			EurekaServerHttpClientFactory eurekaServerHttpClientFactory) {
-		this.eurekaClient.getApplications(); // force initialization
-		return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig, serverCodecs, this.eurekaClient,
+			EurekaServerHttpClientFactory eurekaServerHttpClientFactory,
+			EurekaInstanceConfigBean eurekaInstanceConfigBean) {
+		if (!eurekaInstanceConfigBean.isSkipForcedClientInitialization()) {
+			this.eurekaClient.getApplications(); // force initialization
+		}
+
+		return new InstanceRegistry(this.eurekaServerConfig,
+				this.eurekaClientConfig,
+				serverCodecs,
+				this.eurekaClient,
 				eurekaServerHttpClientFactory,
 				this.instanceRegistryProperties.getExpectedNumberOfClientsSendingRenews(),
 				this.instanceRegistryProperties.getDefaultOpenForTrafficCount());

spring-cloud-netflix-eureka-server/src/test/java/org/springframework/cloud/netflix/eureka/server/EurekaServerAutoConfigurationTests.java

@@ -0,0 +1,72 @@
+package org.springframework.cloud.netflix.eureka.server;
+
+import com.netflix.discovery.EurekaClient;
+import com.netflix.discovery.EurekaClientConfig;
+import com.netflix.eureka.EurekaServerConfig;
+import com.netflix.eureka.resources.ServerCodecs;
+import com.netflix.eureka.transport.EurekaServerHttpClientFactory;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean;
+
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class EurekaServerAutoConfigurationTests {
+
+	@Mock
+	private EurekaServerConfig eurekaServerConfig;
+
+	@Mock
+	private EurekaClientConfig eurekaClientConfig;
+
+	@Mock
+	private EurekaClient eurekaClient;
+
+	@Mock
+	private InstanceRegistryProperties instanceRegistryProperties;
+
+	@Mock
+	private ServerCodecs serverCodecs;
+
+	@Mock
+	private EurekaServerHttpClientFactory eurekaServerHttpClientFactory;
+
+	@Mock
+	private EurekaInstanceConfigBean eurekaInstanceConfigBean;
+
+	@InjectMocks
+	private EurekaServerAutoConfiguration eurekaServerAutoConfiguration;
+
+	@BeforeEach
+	void setup() {
+		when(eurekaServerConfig.getDeltaRetentionTimerIntervalInMs())
+				.thenReturn(1L);
+	}
+
+	@Test
+	void shouldForceEurekaClientInit() {
+		eurekaServerAutoConfiguration.peerAwareInstanceRegistry(serverCodecs,
+				eurekaServerHttpClientFactory, eurekaInstanceConfigBean);
+
+		verify(eurekaClient).getApplications();
+	}
+
+	@Test
+	void shouldNotForceEurekaClientInit() {
+		when(eurekaInstanceConfigBean.isSkipForcedClientInitialization())
+				.thenReturn(true);
+
+		eurekaServerAutoConfiguration.peerAwareInstanceRegistry(serverCodecs,
+				eurekaServerHttpClientFactory, eurekaInstanceConfigBean);
+
+		verify(eurekaClient, never()).getApplications();
+	}
+}