[#73] Added Fallback for enpoint locating. FIxes #73

spring-cloud-sleuth-zipkin/pom.xml

@@ -56,6 +56,12 @@
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.assertj</groupId>
+			<artifactId>assertj-core</artifactId>
+			<version>2.1.0</version>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 
 </project>

spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin/FallbackHavingEndpointLocator.java

@@ -0,0 +1,34 @@
+package org.springframework.cloud.sleuth.zipkin;
+
+import com.twitter.zipkin.gen.Endpoint;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * Endpoint locator that will try to call an endpoint via Discovery Client
+ * and will fallback to Server Properties if an exception is thrown
+ */
+@Slf4j
+public class FallbackHavingEndpointLocator implements EndpointLocator {
+
+	private final DiscoveryClientEndpointLocator discoveryClientEndpointLocator;
+	private final ServerPropertiesEndpointLocator serverPropertiesEndpointLocator;
+
+	public FallbackHavingEndpointLocator(DiscoveryClientEndpointLocator discoveryClientEndpointLocator,
+										 ServerPropertiesEndpointLocator serverPropertiesEndpointLocator) {
+		this.discoveryClientEndpointLocator = discoveryClientEndpointLocator;
+		this.serverPropertiesEndpointLocator = serverPropertiesEndpointLocator;
+	}
+
+	@Override
+	public Endpoint local() {
+		if (discoveryClientEndpointLocator == null) {
+			return serverPropertiesEndpointLocator.local();
+		}
+		try {
+			return discoveryClientEndpointLocator.local();
+		} catch (Exception e) {
+			log.warn("Exception occurred while trying to fetch the Zipkin process endpoint. Falling back to server properties endpoint locator.", e);
+			return serverPropertiesEndpointLocator.local();
+		}
+	}
+}

spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin/ZipkinAutoConfiguration.java

@@ -84,10 +84,15 @@ public class ZipkinAutoConfiguration {
 
 		@Bean
 		public EndpointLocator zipkinEndpointLocator() {
+			return new FallbackHavingEndpointLocator(discoveryClientEndpointLocator(),
+					new ServerPropertiesEndpointLocator(this.serverProperties));
+		}
+
+		private DiscoveryClientEndpointLocator discoveryClientEndpointLocator() {
 			if (this.client!=null) {
 				return new DiscoveryClientEndpointLocator(this.client);
 			}
-			return new ServerPropertiesEndpointLocator(this.serverProperties);
+			return null;
 		}
 
 	}

spring-cloud-sleuth-zipkin/src/test/java/org/springframework/cloud/sleuth/zipkin/FallbackHavingEndpointLocatorTest.java

@@ -0,0 +1,53 @@
+package org.springframework.cloud.sleuth.zipkin;
+
+import com.twitter.zipkin.gen.Endpoint;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.BDDMockito;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+@RunWith(MockitoJUnitRunner.class)
+public class FallbackHavingEndpointLocatorTest {
+
+	@Mock DiscoveryClientEndpointLocator discoveryClientEndpointLocator;
+	@Mock ServerPropertiesEndpointLocator serverPropertiesEndpointLocator;
+	Endpoint expectedEndpoint = new Endpoint();
+
+	@Test
+	public void should_use_system_property_locator_if_discovery_client_locator_is_not_present() {
+		BDDMockito.given(serverPropertiesEndpointLocator.local()).willReturn(expectedEndpoint);
+		FallbackHavingEndpointLocator sut = new FallbackHavingEndpointLocator(null,
+				serverPropertiesEndpointLocator);
+
+		Endpoint endpoint = sut.local();
+
+		then(endpoint).isSameAs(expectedEndpoint);
+	}
+
+	@Test
+	public void should_use_system_property_locator_if_discovery_client_locator_throws_an_exception() {
+		BDDMockito.given(discoveryClientEndpointLocator.local()).willThrow(new RuntimeException());
+		BDDMockito.given(serverPropertiesEndpointLocator.local()).willReturn(expectedEndpoint);
+		FallbackHavingEndpointLocator sut = new FallbackHavingEndpointLocator(discoveryClientEndpointLocator,
+				serverPropertiesEndpointLocator);
+
+		Endpoint endpoint = sut.local();
+
+		then(endpoint).isSameAs(expectedEndpoint);
+	}
+
+	@Test
+	public void should_use_discovery_client_locator_by_default() {
+		BDDMockito.given(discoveryClientEndpointLocator.local()).willReturn(expectedEndpoint);
+		BDDMockito.given(serverPropertiesEndpointLocator.local()).willThrow(new RuntimeException());
+		FallbackHavingEndpointLocator sut = new FallbackHavingEndpointLocator(discoveryClientEndpointLocator,
+				serverPropertiesEndpointLocator);
+
+		Endpoint endpoint = sut.local();
+
+		then(endpoint).isSameAs(expectedEndpoint);
+	}
+}