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.datasource;
  
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  
  import com.alibaba.csp.sentinel.concurrent.NamedThreadFactory;
  import com.alibaba.csp.sentinel.log.RecordLog;
  
  /**
   * A {@link ReadableDataSource} automatically fetches the backend data.
   *
   * @param <S> source data type
   * @param <T> target data type
   * @author Carpenter Lee
   */
  public abstract class AutoRefreshDataSource<S, T> extends AbstractDataSource<S, T> {
  
      private ScheduledExecutorService service;
      protected long recommendRefreshMs = 3000;
  
      public AutoRefreshDataSource(Converter<S, T> configParser) {
          super(configParser);
          startTimerService();
      }
  
      public AutoRefreshDataSource(Converter<S, T> configParser, final long recommendRefreshMs) {
          super(configParser);
          if (recommendRefreshMs <= 0) {
              throw new IllegalArgumentException("recommendRefreshMs must > 0, but " + recommendRefreshMs + " get");
          }
          this.recommendRefreshMs = recommendRefreshMs;
          startTimerService();
      }
  
      @SuppressWarnings("PMD.ThreadPoolCreationRule")
      private void startTimerService() {
          service = Executors.newScheduledThreadPool(1,
              new NamedThreadFactory("sentinel-datasource-auto-refresh-task", true));
          service.scheduleAtFixedRate(new Runnable() {
              @Override
              public void run() {
                  try {
                      if (!isModified()) {
                          return;
                      }
                      T newValue = loadConfig();
                      getProperty().updateValue(newValue);
                  } catch (Throwable e) {
                      RecordLog.info("loadConfig exception", e);
                  }
              }
          }, recommendRefreshMs, recommendRefreshMs, TimeUnit.MILLISECONDS);
      }
  
      @Override
      public void close() throws Exception {
          if (service != null) {
              service.shutdownNow();
              service = null;
          }
      }
  
      protected boolean isModified() {
          return true;
      }
  }
  