refactor(registry-etcd): Refactor the EtcdDiscovery class and update …

…related components

- Refactor the findServiceInstances method and use SingletonManager to manage watchers
- Optimize the output format of exception information in log records
- Update the Etcd image version in the test environment
- Removed redundant information in README.md - Added SingletonManager class for managing singleton objects

demo/demo-etcd/README.md

@@ -2,5 +2,4 @@
 
 This integration tests is designed for Etcd registry and configuration. And extra test cases include:
 
-* Test cases related to SpringMVC annotations that demo-springmvc can not cover. 
-
+* Test cases related to SpringMVC annotations that demo-springmvc can not cover.

demo/demo-etcd/test-client/pom.xml

@@ -60,7 +60,8 @@
               <configuration>
                 <images>
                   <image>
-                    <name>etcd:3.5.9</name>
+<!--                    <name>etcd:3.5.9</name>-->
+                    <name>bitnami/etcd:latest</name>
                     <alias>etcd</alias>
                     <run>
                       <namingStrategy>alias</namingStrategy>

service-registry/registry-etcd/pom.xml

@@ -49,4 +49,4 @@
     </dependency>
   </dependencies>
 
-</project>
+</project>

service-registry/registry-etcd/src/main/java/org/apache/servicecomb/registry/etcd/EtcdDiscovery.java

@@ -85,7 +85,7 @@ public boolean enabled(String application, String serviceName) {
   public List<EtcdDiscoveryInstance> findServiceInstances(String application, String serviceName) {
 
     String prefixPath = basePath + "/" + application + "/" + serviceName;
-    if (!isWatch) {
+    SingletonManager.getInstance().getSingleton(prefixPath, serName -> {
       Watch watchClient = client.getWatchClient();
       try {
         watchClient.watch(ByteSequence.from(prefixPath, Charset.defaultCharset()), WatchOption.builder().build(),
@@ -94,11 +94,11 @@ public List<EtcdDiscoveryInstance> findServiceInstances(String application, Stri
               instanceChangedListener.onInstanceChanged(name(), application, serviceName,
                   convertServiceInstanceList(keyValueList));
             });
-        isWatch = true;
       } catch (Exception e) {
         LOGGER.error("add watch failure", e);
       }
-    }
+      return watchClient;
+    });
     List<KeyValue> endpointKv = getValuesByPrefix(prefixPath);
     return convertServiceInstanceList(endpointKv);
   }
@@ -110,7 +110,7 @@ public List<KeyValue> getValuesByPrefix(String prefix) {
             GetOption.builder().withPrefix(ByteSequence.from(prefix, StandardCharsets.UTF_8)).build());
     GetResponse response = MuteExceptionUtil.builder().withLog("get kv by prefix error")
         .executeCompletableFuture(getFuture);
-    return response.getKvs(); // 返回所有匹配前缀的键值对
+    return response.getKvs();
   }
 
   private List<EtcdDiscoveryInstance> convertServiceInstanceList(List<KeyValue> keyValueList) {

service-registry/registry-etcd/src/main/java/org/apache/servicecomb/registry/etcd/MuteExceptionUtil.java

@@ -55,7 +55,7 @@ public <T, R> R executeFunction(FunctionWithException<T, R> function, T t) {
       try {
         return function.apply(t);
       } catch (Exception e) {
-        LOGGER.error(getLogMessage("execute Function failure..."), customMessageParams,  e);
+        LOGGER.error(getLogMessage("execute Function failure..."), customMessageParams, e);
         return null;
       }
     }
@@ -73,7 +73,7 @@ public <T> T executeCompletableFuture(CompletableFuture<T> completableFuture) {
       try {
         return completableFuture.get();
       } catch (Exception e) {
-        LOGGER.error(getLogMessage("execute CompletableFuture failure..."),customMessageParams, e);
+        LOGGER.error(getLogMessage("execute CompletableFuture failure..."), customMessageParams, e);
         return null;
       }
     }
@@ -82,7 +82,7 @@ public <T1, T2, R> R executeFunctionWithDoubleParam(FunctionWithDoubleParam<T1,
       try {
         return function.apply(t1, t2);
       } catch (Exception e) {
-        LOGGER.error(getLogMessage("execute FunctionWithDoubleParam failure..."),customMessageParams, e);
+        LOGGER.error(getLogMessage("execute FunctionWithDoubleParam failure..."), customMessageParams, e);
         return null;
       }
     }

service-registry/registry-etcd/src/main/java/org/apache/servicecomb/registry/etcd/SingletonManager.java

@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.servicecomb.registry.etcd;
+
+import java.util.function.Function;
+
+import org.apache.servicecomb.foundation.common.concurrent.ConcurrentHashMapEx;
+
+public class SingletonManager {
+
+  private static SingletonManager instance;
+
+  private ConcurrentHashMapEx<String, Object> singletons = new ConcurrentHashMapEx<>();
+
+  private SingletonManager() {
+  }
+
+  public static synchronized SingletonManager getInstance() {
+    if (instance == null) {
+      instance = new SingletonManager();
+    }
+    return instance;
+  }
+
+  public <T> T getSingleton(String key, Function<? super String, ? extends T> mappingFunction) {
+    return (T) singletons.computeIfAbsent(key, mappingFunction);
+  }
+
+  public void destroy() {
+    singletons.clear();
+    instance = null;
+  }
+}