content: /*
   * 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.cassandra.utils;
  
  import java.util.concurrent.TimeUnit;
  
  import org.apache.cassandra.io.util.File;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.concurrent.ScheduledExecutors;
  
  public class ResourceWatcher
  {
      public static void watch(String resource, Runnable callback, int period)
      {
          ScheduledExecutors.scheduledTasks.scheduleWithFixedDelay(new WatchedResource(resource, callback), period, period, TimeUnit.MILLISECONDS);
      }
  
      public static class WatchedResource implements Runnable
      {
          private static final Logger logger = LoggerFactory.getLogger(WatchedResource.class);
          private final String resource;
          private final Runnable callback;
          private long lastLoaded;
  
          public WatchedResource(String resource, Runnable callback)
          {
              this.resource = resource;
              this.callback = callback;
              lastLoaded = 0;
          }
  
          public void run()
          {
              try
              {
                  String filename = FBUtilities.resourceToFile(resource);
                  long lastModified = new File(filename).lastModified();
                  if (lastModified > lastLoaded)
                  {
                      callback.run();
                      lastLoaded = lastModified;
                  }
              }
              catch (Throwable t)
              {
                  JVMStabilityInspector.inspectThrowable(t);
                  logger.error(String.format("Timed run of %s failed.", callback.getClass()), t);
              }
          }
      }
  }
  