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/*
* 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.oodt.commons.activity;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
/**
* A history of incidents to be stored in long-term storage.
*
* The History tracks Incidents that occurred during the course of an
* activity. It's a temporary container for incidents before the activity is deemed
* complete and stored into whatever the long-term {@link Storage} is. A
* History starts out with at least one {@link Incident} received from
* (usually remote) processing. Other incidents arrive through {@link #addIncident} and
* must have the same ID. Eventually, one of those incidents will be an
* ActivityStopped incident, which then schedules the History to commit
* itself.
*
* It doesn't commit itself right away though; other incidents may arrive that are part
* of the activity out of order, so there's a delay of {@link #closeTime} milliseconds
* before it's sent to {@link Storage}. Other incidents will be recorded during this delay.
*
*
It's also possible that the ActivityStopped incident never arrives from
* the process that deems the activity stopped. In that case, the idle timer (which is
* reset whenever an incident arrives) determines when to put the History
* into its commital state. The stop can arrive after this point (and will be recorded),
* but it otherwise doesn't affect the commit-to-close time.
*
* @author Kelly
* @version $Revision: 1.1 $
*/
final class History {
/**
* Creates a new {@link History} instance.
*
* @param initialIncident Incident which gives the history its ID.
* @param storage Where to store the incidents when the history's done.
*/
History(Incident initialIncident, Storage storage) {
id = initialIncident.getActivityID();
this.storage = storage;
incidents.add(initialIncident);
scheduleExpiration();
}
/**
* Add an incident to this history.
*
* @param incident an {@link Incident} value.
*/
synchronized void addIncident(Incident incident) {
if (!incident.getActivityID().equals(id)) {
throw new IllegalArgumentException("Incident's activity ID " + incident.getActivityID()
+ " doesn't match History's ID " + id);
}
if (incidents == null) {
return;
}
incidents.add(incident);
if (expireHistoryTask != null) {
expireHistoryTask.cancel();
}
if (incident instanceof ActivityStopped) {
commit();
} else if (closeHistoryTask == null) {
scheduleExpiration();
}
}
/**
* Commit this history by starting the commit-to-close timer.
*/
private void commit() {
if (closeHistoryTask != null) {
return;
}
TIMER.schedule(closeHistoryTask = new CloseHistoryTask(), closeTime);
}
/**
* Schedule expiration of this history due to idleness.
*/
private void scheduleExpiration() {
TIMER.schedule(expireHistoryTask = new ExpireHistoryTask(), idleTime);
}
/**
* Close this history out by storing the incidents to long-term storage.
*/
private synchronized void close() {
Collections.sort(incidents);
storage.store(id, incidents);
incidents = null;
}
/** History's ID. */
private String id;
/** In what long-term storage to store incidents. */
private Storage storage;
/** Timer task that expires an idle history. If null, this history is in commit-to-close state. */
private ExpireHistoryTask expireHistoryTask;
/** Timer task to close a history. If nonnull, this history is in commit-to-close state. */
private CloseHistoryTask closeHistoryTask;
/** Incidents to store. */
private List incidents = new ArrayList();
/**
* Timer task that expires (commits and closes) an idle history.
*/
private class ExpireHistoryTask extends TimerTask {
public void run() {
synchronized (History.this) {
// Check to see if a new expireHistoryTask got generated.
// If it did, it means a new incident got logged while we
// were about to expire the history. But if the history's
// current expiration task is this task, then we're clear
// to commit the history, and any incidents that arrive
// won't reset it.
if (expireHistoryTask == this) {
commit();
}
}
}
}
/**
* Timer task that gives time for more incidents to arrive before closing forever a history.
*/
private class CloseHistoryTask extends TimerTask {
public void run() {
close();
}
}
/** Only timer we'll ever need. */
private static final Timer TIMER = new Timer(/*isDaemon*/true);
/** How many milliseconds to wait before giving up on an idle history. */
static long idleTime = Long.getLong("org.apache.oodt.commons.activity.History.idle", 5 * 60 * 1000);
/** How many milliseconds to wait to give a history extra time to receive incidents before saving it to storage. */
static long closeTime = Long.getLong("org.apache.oodt.commons.activity.History.close", 5 * 60 * 1000);
}