perf: speed up startup when meet timeout of meta service and config service

lazy init

Author: Anilople

apollo-client/src/main/java/com/ctrip/framework/apollo/internals/ConfigServiceLocator.java

@@ -22,14 +22,14 @@
 import com.ctrip.framework.apollo.core.utils.DeprecatedPropertyNotifyUtil;
 import com.ctrip.framework.foundation.Foundation;
 import java.lang.reflect.Type;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import com.ctrip.framework.apollo.build.ApolloInjector;
 import com.ctrip.framework.apollo.core.dto.ServiceDTO;
@@ -54,25 +54,33 @@ public class ConfigServiceLocator {
   private static final Logger logger = DeferredLoggerFactory.getLogger(ConfigServiceLocator.class);
   private HttpClient m_httpClient;
   private ConfigUtil m_configUtil;
-  private AtomicReference<List<ServiceDTO>> m_configServices;
-  private Type m_responseType;
-  private ScheduledExecutorService m_executorService;
+  private final AtomicReference<List<ServiceDTO>> m_configServices = new AtomicReference<>(
+      Collections.emptyList());
+  private static final Type m_responseType = new TypeToken<List<ServiceDTO>>() {
+  }.getType();
+  ScheduledExecutorService m_executorService;
   private static final Joiner.MapJoiner MAP_JOINER = Joiner.on("&").withKeyValueSeparator("=");
   private static final Escaper queryParamEscaper = UrlEscapers.urlFormParameterEscaper();
 
   /**
    * Create a config service locator.
    */
   public ConfigServiceLocator() {
-    List<ServiceDTO> initial = Lists.newArrayList();
-    m_configServices = new AtomicReference<>(initial);
-    m_responseType = new TypeToken<List<ServiceDTO>>() {
-    }.getType();
-    m_httpClient = ApolloInjector.getInstance(HttpClient.class);
-    m_configUtil = ApolloInjector.getInstance(ConfigUtil.class);
-    this.m_executorService = Executors.newScheduledThreadPool(1,
-        ApolloThreadFactory.create("ConfigServiceLocator", true));
-    initConfigServices();
+  }
+
+  /**
+   * only init once.
+   */
+  private void initialize() {
+    if (m_httpClient == null) {
+      synchronized (this) {
+        if (m_httpClient == null) {
+          m_httpClient = ApolloInjector.getInstance(HttpClient.class);
+          m_configUtil = ApolloInjector.getInstance(ConfigUtil.class);
+          initConfigServices();
+        }
+      }
+    }
   }
 
   private void initConfigServices() {
@@ -160,8 +168,14 @@ private String getDeprecatedCustomizedConfigService() {
    * @return the services dto
    */
   public List<ServiceDTO> getConfigServices() {
+    initialize();
     if (m_configServices.get().isEmpty()) {
-      updateConfigServices();
+      // quick fail
+      throw new ApolloConfigException(
+          "No available config service, "
+              + "server side maybe crash or network cannot connect to server from this ip, "
+          + "one of meta service url is " + assembleMetaServiceUrl()
+      );
     }
 
     return m_configServices.get();
@@ -178,6 +192,8 @@ private boolean tryUpdateConfigServices() {
   }
 
   private void schedulePeriodicRefresh() {
+    this.m_executorService = Executors.newScheduledThreadPool(1,
+        ApolloThreadFactory.create("ConfigServiceLocator", true));
     this.m_executorService.scheduleAtFixedRate(
         new Runnable() {
           @Override
@@ -190,7 +206,7 @@ public void run() {
         m_configUtil.getRefreshIntervalTimeUnit());
   }
 
-  private synchronized void updateConfigServices() {
+  synchronized void updateConfigServices() {
     String url = assembleMetaServiceUrl();
 
     HttpRequest request = new HttpRequest(url);