| /* |
| * 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 <em>previous exception</em> 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 |
| } |
| |
| } |