org.apache.hadoop.security.ssl.FileMonitoringTimerTask Maven / Gradle / Ivy
/**
* 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.hadoop.security.ssl;
import org.apache.hadoop.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions;
import org.apache.hadoop.classification.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.TimerTask;
import java.util.function.Consumer;
/**
* Implements basic logic to track when a file changes on disk and call the action
* passed to the constructor when it does. An exception handler can optionally also be specified
* in the constructor, otherwise any exception occurring during process will be logged
* using this class' logger.
*/
@InterfaceAudience.Private
public class FileMonitoringTimerTask extends TimerTask {
static final Logger LOG = LoggerFactory.getLogger(FileMonitoringTimerTask.class);
@VisibleForTesting
static final String PROCESS_ERROR_MESSAGE =
"Could not process file change : ";
final private List filePaths;
final private Consumer onFileChange;
final Consumer onChangeFailure;
private List lastProcessed;
/**
* See {@link #FileMonitoringTimerTask(List, Consumer, Consumer)}.
*
* @param filePath The file to monitor.
* @param onFileChange What to do when the file changes.
* @param onChangeFailure What to do when onFileChange
* throws an exception.
*/
public FileMonitoringTimerTask(Path filePath, Consumer onFileChange,
Consumer onChangeFailure) {
this(Collections.singletonList(filePath), onFileChange, onChangeFailure);
}
/**
* Create file monitoring task to be scheduled using a standard
* Java {@link java.util.Timer} instance.
*
* @param filePaths The path to the file to monitor.
* @param onFileChange The function to call when the file has changed.
* @param onChangeFailure The function to call when an exception is
* thrown during the file change processing.
*/
public FileMonitoringTimerTask(List filePaths,
Consumer onFileChange,
Consumer onChangeFailure) {
Preconditions.checkNotNull(filePaths,
"path to monitor disk file is not set");
Preconditions.checkNotNull(onFileChange,
"action to monitor disk file is not set");
this.filePaths = new ArrayList(filePaths);
this.lastProcessed = new ArrayList();
this.filePaths.forEach(path ->
this.lastProcessed.add(path.toFile().lastModified()));
this.onFileChange = onFileChange;
this.onChangeFailure = onChangeFailure;
}
@Override
public void run() {
int modified = -1;
for (int i = 0; i < filePaths.size() && modified < 0; i++) {
if (lastProcessed.get(i) != filePaths.get(i).toFile().lastModified()) {
modified = i;
}
}
if (modified > -1) {
Path filePath = filePaths.get(modified);
try {
onFileChange.accept(filePath);
} catch (Throwable t) {
if (onChangeFailure != null) {
onChangeFailure.accept(t);
} else {
LOG.error(PROCESS_ERROR_MESSAGE + filePath.toString(), t);
}
}
lastProcessed.set(modified, filePath.toFile().lastModified());
}
}
}