Adds failover data centers to DiscoveryClient. Fixes gh-712

spring-cloud-consul-discovery/src/main/java/org/springframework/cloud/consul/discovery/ConsulDiscoveryClient.java

@@ -32,6 +32,7 @@
 import org.springframework.cloud.client.DefaultServiceInstance;
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.util.CollectionUtils;
 
 import static org.springframework.cloud.consul.discovery.ConsulServerUtils.findHost;
 import static org.springframework.cloud.consul.discovery.ConsulServerUtils.getMetadata;
@@ -62,8 +63,17 @@ public String description() {
 
 	@Override
 	public List<ServiceInstance> getInstances(final String serviceId) {
-		return getInstances(serviceId,
-				new QueryParams(this.properties.getConsistencyMode()));
+
+		List<ServiceInstance> instances = getInstances(serviceId,
+			new QueryParams(this.properties.getConsistencyMode()));
+
+		if (CollectionUtils.isEmpty(instances) && !CollectionUtils.isEmpty(this.properties.getFailoverDataCenters())) {
+			for (String dc : this.properties.getFailoverDataCenters()) {
+				instances.addAll(getInstances(serviceId, new QueryParams(dc, this.properties.getConsistencyMode())));
+			}
+		}
+
+		return instances;
 	}
 
 	public List<ServiceInstance> getInstances(final String serviceId,

spring-cloud-consul-discovery/src/main/java/org/springframework/cloud/consul/discovery/ConsulDiscoveryProperties.java

@@ -204,6 +204,12 @@ public class ConsulDiscoveryProperties {
 	 */
 	private int order = 0;
 
+	/**
+	 * List of data centers to look for service instances in, if there are
+	 * no instances of wanted service in local data center.
+	 */
+	private List<String> failoverDataCenters;
+
 	@SuppressWarnings("unused")
 	private ConsulDiscoveryProperties() {
 		this.managementTags.add(MANAGEMENT);
@@ -589,6 +595,14 @@ public void setManagementEnableTagOverride(Boolean managementEnableTagOverride)
 		this.managementEnableTagOverride = managementEnableTagOverride;
 	}
 
+	public List<String> getFailoverDataCenters() {
+		return this.failoverDataCenters;
+	}
+
+	public void setFailoverDataCenters(List<String> failoverDataCenters) {
+		this.failoverDataCenters = failoverDataCenters;
+	}
+
 	@Override
 	public String toString() {
 		return new ToStringCreator(this).append("hostInfo", this.hostInfo)
@@ -626,6 +640,7 @@ public String toString() {
 				.append("register", this.register).append("deregister", this.deregister)
 				.append("registerHealthCheck", this.registerHealthCheck)
 				.append("failFast", this.failFast)
+				.append("failoverDataCenters", this.failoverDataCenters)
 				.append("healthCheckTlsSkipVerify", this.healthCheckTlsSkipVerify)
 				.append("order", this.order).append("tagsAsMetadata", this.tagsAsMetadata)
 				.append("enableTagOverride", this.enableTagOverride)

spring-cloud-consul-discovery/src/test/java/org/springframework/cloud/consul/discovery/ConsulDiscoveryClientMultipleDataCentersTests.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.consul.discovery;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+import com.ecwid.consul.v1.ConsulClient;
+import com.ecwid.consul.v1.Response;
+import com.ecwid.consul.v1.health.model.HealthService;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mockito;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.util.StringUtils;
+
+import static java.util.Collections.singletonList;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.argThat;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.lenient;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+
+/**
+ * @author Vojislav Cuk
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(
+		properties = { "spring.application.name=testConsulDiscovery",
+				"spring.cloud.consul.discovery.prefer-ip-address=true",
+				"spring.cloud.consul.discovery.metadata[foo]=bar",
+				"spring.cloud.consul.discovery.failoverDataCenters[0]=dc2" },
+		webEnvironment = RANDOM_PORT)
+public class ConsulDiscoveryClientMultipleDataCentersTests {
+
+	@Autowired
+	private ConsulDiscoveryClient discoveryClient;
+
+	@MockBean
+	private ConsulClient consulClient;
+
+	@Test
+	public void getInstancesShouldReturnEmptyListWhenThereAreNoInstancesInLocalNorFailoverDataCenters() {
+
+		Mockito.when(consulClient.getHealthServices(eq("testService"), any())).thenReturn(
+				new Response<>(new ArrayList<>(), 0L, true, System.currentTimeMillis()));
+
+		assertThat(discoveryClient.getInstances("testService")).isEmpty();
+	}
+
+	@Test
+	public void getInstancesShouldReturnInstancesFromFailoverDataCentersWhenNoInstanceInLocalDataCenterIsAvailable() {
+
+		Mockito.when(consulClient.getHealthServices(eq("testService"),
+				argThat(r -> !StringUtils.hasLength(r.getDatacenter()))))
+				.thenReturn(new Response<>(new ArrayList<>(), 0L, true,
+						System.currentTimeMillis()));
+
+		Response<List<HealthService>> response = consulInstancesResponse();
+		Mockito.when(consulClient.getHealthServices(eq("testService"),
+				argThat(r -> Objects.equals(r.getQueryParams().getDatacenter(), "dc2"))))
+				.thenReturn(response);
+
+		assertThat(discoveryClient.getInstances("testService")).isNotEmpty();
+	}
+
+	private Response<List<HealthService>> consulInstancesResponse() {
+
+		HealthService healthService = mock(HealthService.class);
+		HealthService.Service service = mock(HealthService.Service.class);
+
+		when(healthService.getService()).thenReturn(service);
+		when(service.getAddress()).thenReturn("localhost");
+		when(service.getPort()).thenReturn(443);
+		lenient().when(service.getTags()).thenReturn(singletonList("secure=true"));
+
+		return new Response<>(singletonList(healthService), 0L, true,
+				System.currentTimeMillis());
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@EnableAutoConfiguration
+	@EnableDiscoveryClient
+	public static class MyTestConfig {
+
+	}
+
+}