[huaweicloud#1207]support fallback address for isolation

spring-cloud-huawei-governance/src/main/java/com/huaweicloud/governance/adapters/loadbalancer/FallbackDiscoveryProperties.java

@@ -0,0 +1,78 @@
+/*
+
+ * Copyright (C) 2020-2024 Huawei Technologies Co., Ltd. All rights reserved.
+
+ * 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
+ *
+ *     http://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 com.huaweicloud.governance.adapters.loadbalancer;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.cloud.client.DefaultServiceInstance;
+import org.springframework.cloud.client.ServiceInstance;
+
+/**
+ * Configures fallback address if discovery client do not find any instance or all
+ * instances are isolated.
+ */
+@ConfigurationProperties(prefix = "spring.cloud.discovery.client.fallback")
+public class FallbackDiscoveryProperties implements InitializingBean {
+  private Map<String, DefaultServiceInstance> instances = new HashMap<>();
+
+  private boolean enabled = false;
+
+  private DefaultServiceInstance global;
+
+  public Map<String, DefaultServiceInstance> getInstances() {
+    return this.instances;
+  }
+
+  public void setInstances(Map<String, DefaultServiceInstance> instances) {
+    this.instances = instances;
+  }
+
+  public boolean isEnabled() {
+    return enabled;
+  }
+
+  public void setEnabled(boolean enabled) {
+    this.enabled = enabled;
+  }
+
+  public DefaultServiceInstance getGlobal() {
+    return global;
+  }
+
+  public void setGlobal(DefaultServiceInstance global) {
+    this.global = global;
+  }
+
+  @Override
+  public void afterPropertiesSet() {
+    for (Entry<String, DefaultServiceInstance> entry : instances.entrySet()) {
+      entry.getValue().setServiceId(entry.getKey());
+    }
+  }
+
+  public ServiceInstance readFallbackServiceInstance(String serviceId) {
+    if (this.instances.get(serviceId) != null) {
+      return this.instances.get(serviceId);
+    }
+    return global;
+  }
+}

spring-cloud-huawei-governance/src/main/java/com/huaweicloud/governance/adapters/loadbalancer/InstanceIsolationServiceInstanceFilter.java

@@ -39,12 +39,17 @@ public class InstanceIsolationServiceInstanceFilter implements ServiceInstanceFi
 
   private final Environment env;
 
-  public InstanceIsolationServiceInstanceFilter(Environment environment) {
+  private final FallbackDiscoveryProperties fallbackDiscoveryProperties;
+
+  public InstanceIsolationServiceInstanceFilter(Environment environment,
+      FallbackDiscoveryProperties fallbackDiscoveryProperties) {
     this.env = environment;
+    this.fallbackDiscoveryProperties = fallbackDiscoveryProperties;
     EventManager.register(this);
   }
 
   @Subscribe
+  @SuppressWarnings("unused")
   public void onInstanceIsolatedEvent(InstanceIsolatedEvent event) {
     synchronized (lock) {
       for (Iterator<String> iterator = isolatedInstances.keySet().iterator(); iterator.hasNext(); ) {
@@ -62,7 +67,10 @@ public void onInstanceIsolatedEvent(InstanceIsolatedEvent event) {
   @Override
   public List<ServiceInstance> filter(ServiceInstanceListSupplier supplier, List<ServiceInstance> instances,
       Request<?> request) {
-    if (isolatedInstances.isEmpty() || instances.isEmpty()) {
+    if (instances.isEmpty()) {
+      return fallbackServiceInstance(supplier, instances);
+    }
+    if (isolatedInstances.isEmpty()) {
       return instances;
     }
     List<ServiceInstance> result = new ArrayList<>(instances.size());
@@ -84,11 +92,20 @@ public List<ServiceInstance> filter(ServiceInstanceListSupplier supplier, List<S
     }
 
     if (result.isEmpty()) {
-      return instances;
+      return fallbackServiceInstance(supplier, instances);
     }
     return result;
   }
 
+  private List<ServiceInstance> fallbackServiceInstance(ServiceInstanceListSupplier supplier,
+      List<ServiceInstance> instances) {
+    if (fallbackDiscoveryProperties.isEnabled()
+        && fallbackDiscoveryProperties.readFallbackServiceInstance(supplier.getServiceId()) != null) {
+      return List.of(fallbackDiscoveryProperties.readFallbackServiceInstance(supplier.getServiceId()));
+    }
+    return instances;
+  }
+
   @Override
   public int getOrder() {
     return env.getProperty("spring.cloud.loadbalance.filter.instance-isolation.order", int.class, -300);

spring-cloud-huawei-governance/src/main/java/com/huaweicloud/governance/adapters/loadbalancer/LoadbalancerConfiguration.java

@@ -50,7 +50,13 @@ public LoadBalancerRequestFactory loadBalancerRequestFactory(LoadBalancerClient
   }
 
   @Bean
-  public InstanceIsolationServiceInstanceFilter instanceIsolationServiceInstanceFilter(Environment environment) {
-    return new InstanceIsolationServiceInstanceFilter(environment);
+  public InstanceIsolationServiceInstanceFilter instanceIsolationServiceInstanceFilter(Environment environment,
+      FallbackDiscoveryProperties fallbackDiscoveryProperties) {
+    return new InstanceIsolationServiceInstanceFilter(environment, fallbackDiscoveryProperties);
+  }
+
+  @Bean
+  public FallbackDiscoveryProperties fallbackDiscoveryProperties() {
+    return new FallbackDiscoveryProperties();
   }
 }