package org.apache.cassandra.utils;
/*
*
* 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.
*
*/
import java.io.File;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.service.StorageService;
public class ResourceWatcher
{
public static void watch(String resource, Runnable callback, int period)
{
StorageService.scheduledTasks.scheduleWithFixedDelay(new WatchedResource(resource, callback), period, period, TimeUnit.MILLISECONDS);
}
public static class WatchedResource implements Runnable
{
private static Logger logger = LoggerFactory.getLogger(WatchedResource.class);
private String resource;
private 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)
{
logger.error(String.format("Timed run of %s failed.", callback.getClass()), t);
}
}
}
}