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This bundle is the core implementation of the Karaf features support.
/*
* 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.karaf.features.internal.download.impl;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public abstract class AbstractRetryableDownloadTask extends AbstractDownloadTask {
private static final Logger LOGGER = LoggerFactory.getLogger(AbstractRetryableDownloadTask.class);
private long scheduleDelay = 250;
private int scheduleMaxRun = 9;
private int scheduleNbRun = 0;
private Exception previousException = null;
public AbstractRetryableDownloadTask(ScheduledExecutorService executorService, String url) {
super(executorService, url);
}
public long getScheduleDelay() {
return scheduleDelay;
}
public void setScheduleDelay(long scheduleDelay) {
this.scheduleDelay = scheduleDelay;
}
public int getScheduleMaxRun() {
return scheduleMaxRun;
}
public void setScheduleMaxRun(int scheduleMaxRun) {
this.scheduleMaxRun = scheduleMaxRun;
}
public void run() {
try {
try {
File file = download(previousException);
setFile(file);
} catch (IOException e) {
Retry retry = isRetryable(e);
int retryCount = scheduleMaxRun;
if (retry == Retry.QUICK_RETRY) {
retryCount = retryCount / 2; // arbitrary number...
} else if (retry == Retry.NO_RETRY) {
retryCount = 0;
}
if (++scheduleNbRun < retryCount) {
previousException = e;
long delay = (long)(scheduleDelay * 3 / 2 + Math.random() * scheduleDelay / 2);
LOGGER.debug("Error downloading " + url + ": " + e.getMessage() + ". " + retry + " in approx " + delay + " ms.");
executorService.schedule(this, delay, TimeUnit.MILLISECONDS);
scheduleDelay *= 2;
} else {
setException(new IOException("Error downloading " + url, e));
}
}
} catch (Throwable e) {
setException(new IOException("Error downloading " + url, e));
}
}
protected Retry isRetryable(IOException e) {
return Retry.DEFAULT_RETRY;
}
/**
* Abstract download operation that may use previous exception as hint for optimized retry
* @param previousException
* @return
* @throws Exception
*/
protected abstract File download(Exception previousException) throws Exception;
/**
* What kind of retry may be attempted
*/
protected enum Retry {
/** Each retry would lead to the same result */
NO_RETRY,
/** It's ok to retry 2, 3 times, but no more */
QUICK_RETRY,
/** Retry with high expectation of success at some point */
DEFAULT_RETRY
}
}