content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * 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.alibaba.csp.sentinel.init;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.ServiceLoader;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import com.alibaba.csp.sentinel.log.RecordLog;
  import com.alibaba.csp.sentinel.spi.SpiLoader;
  
  /**
   * Load registered init functions and execute in order.
   *
   * @author Eric Zhao
   */
  public final class InitExecutor {
  
      private static AtomicBoolean initialized = new AtomicBoolean(false);
  
      /**
       * If one {@link InitFunc} throws an exception, the init process
       * will immediately be interrupted and the application will exit.
       *
       * The initialization will be executed only once.
       */
      public static void doInit() {
          if (!initialized.compareAndSet(false, true)) {
              return;
          }
          try {
              List<InitFunc> initFuncs = SpiLoader.of(InitFunc.class).loadInstanceListSorted();
              List<OrderWrapper> initList = new ArrayList<OrderWrapper>();
              for (InitFunc initFunc : initFuncs) {
                  RecordLog.info("[InitExecutor] Found init func: {}", initFunc.getClass().getCanonicalName());
                  insertSorted(initList, initFunc);
              }
              for (OrderWrapper w : initList) {
                  w.func.init();
                  RecordLog.info("[InitExecutor] Executing {} with order {}",
                      w.func.getClass().getCanonicalName(), w.order);
              }
          } catch (Exception ex) {
              RecordLog.warn("[InitExecutor] WARN: Initialization failed", ex);
              ex.printStackTrace();
          } catch (Error error) {
              RecordLog.warn("[InitExecutor] ERROR: Initialization failed with fatal error", error);
              error.printStackTrace();
          }
      }
  
      private static void insertSorted(List<OrderWrapper> list, InitFunc func) {
          int order = resolveOrder(func);
          int idx = 0;
          for (; idx < list.size(); idx++) {
              if (list.get(idx).getOrder() > order) {
                  break;
              }
          }
          list.add(idx, new OrderWrapper(order, func));
      }
  
      private static int resolveOrder(InitFunc func) {
          if (!func.getClass().isAnnotationPresent(InitOrder.class)) {
              return InitOrder.LOWEST_PRECEDENCE;
          } else {
              return func.getClass().getAnnotation(InitOrder.class).value();
          }
      }
  
      private InitExecutor() {}
  
      private static class OrderWrapper {
          private final int order;
          private final InitFunc func;
  
          OrderWrapper(int order, InitFunc func) {
              this.order = order;
              this.func = func;
          }
  
          int getOrder() {
              return order;
          }
  
          InitFunc getFunc() {
              return func;
          }
      }
  }
  