// serverAccessTracker.java
// -------------------------------------
// (C) 2009 by Michael Peter Christen; mc@yacy.net
// first published on http://yacy.net
// Frankfurt, Germany, 20.02.2009
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package net.yacy.server;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.LinkedBlockingQueue;
import net.yacy.cora.protocol.Domains;
public class serverAccessTracker {
private static final long cleanupCycle = 60000; // 1 minute
private static long maxTrackingTime = 3600000;
private static int maxTrackingCount = 1000;
private static int maxHostCount = 100;
private static final ConcurrentHashMap<String, Queue<Track>> accessTracker = new ConcurrentHashMap<String, Queue<Track>>(); // mappings from requesting host to an ArrayList of serverTrack-entries
private static long lastCleanup;
private static long lastLocalhostAccess = 0;
public static class Track {
private final long time;
private final String path;
public Track(final long time, final String path) {
this.time = time;
this.path = path;
}
public long getTime() {
return this.time;
}
public String getPath() {
return this.path;
}
}
public static void init(final long mtt, final int mtc, final int mthc) {
maxTrackingTime = mtt;
maxTrackingCount = mtc;
maxHostCount = mthc;
}
/*
* remove all entries from the access tracker where the age of the last access is greater than the given timeout
*/
private static void cleanupAccessTracker() {
if (System.currentTimeMillis() - lastCleanup < cleanupCycle) return; // avoid too many scans of the queues
lastCleanup = System.currentTimeMillis();
// clear entries which had no entry for the maxTrackingTime time
final Iterator<Map.Entry<String, Queue<Track>>> i = accessTracker.entrySet().iterator();
Queue<Track> track;
while (i.hasNext()) {
track = i.next().getValue();
clearTooOldAccess(track);
if (track.isEmpty()) {
// all entries are too old. delete the whole track
i.remove();
} else {
// check if the maxTrackingCount is exceeded
while (track.size() > maxTrackingCount) try {
// delete the oldest entries
track.remove();
} catch (final NoSuchElementException e) { break; } // concurrency may cause that the track is already empty
}
}
// if there are more entries left than maxTrackingCount, delete some.
while (accessTracker.size() > maxHostCount) {
// delete just any
final String key = accessTracker.keys().nextElement();
if (key == null) break; // may occur because of concurrency effects
accessTracker.remove(key);
}
}
/**
* compute the number of accesses to a given host in the latest time
* @param host the host that was accessed
* @param delta the time delta from now to the past where the access times shall be computed
* @return the number of accesses to the host in the given time span
*/
public static int latestAccessCount(final String host, final long delta) {
final Collection<Track> timeList = accessTrack(host);
if (timeList == null) return 0;
final long time = System.currentTimeMillis() - delta;
int c = 0;
for (final Track l: timeList) if ( l != null && l.getTime() > time) c++;
return c;
}
private static void clearTooOldAccess(final Queue<Track> access) {
final long time = System.currentTimeMillis() - maxTrackingTime;
final Iterator<Track> e = access.iterator();
Track l;
int max = access.size(); // ensure termination
while (e.hasNext() && max-- > 0) {
l = e.next();
if (l.getTime() <= time) e.remove();
}
}
public static void track(final String host, String accessPath) {
// check storage size
if (System.currentTimeMillis() - lastCleanup > cleanupCycle) {
cleanupAccessTracker();
}
// learn that a specific host has accessed a specific path
if (accessPath == null) accessPath="NULL";
Queue<Track> track = accessTracker.get(host);
if (track == null) {
track = new LinkedBlockingQueue<Track>();
track.add(new Track(System.currentTimeMillis(), accessPath));
// add to tracker
accessTracker.put(host, track);
} else {
track.add(new Track(System.currentTimeMillis(), accessPath));
clearTooOldAccess(track);
}
if (Domains.isLocalhost(host)) lastLocalhostAccess = System.currentTimeMillis();
}
public static Collection<Track> accessTrack(final String host) {
// returns mapping from Long(accesstime) to path
final Queue<Track> access = accessTracker.get(host);
if (access == null) return null;
// clear too old entries
clearTooOldAccess(access);
if (access.isEmpty()) {
accessTracker.remove(host);
}
return access;
}
public static Iterator<String> accessHosts() {
// returns an iterator of hosts in tracker (String)
final Map<String, Queue<Track>> accessTrackerClone = new ConcurrentHashMap<String, Queue<Track>>();
accessTrackerClone.putAll(accessTracker);
return accessTrackerClone.keySet().iterator();
}
public static long timeSinceAccessFromLocalhost() {
return System.currentTimeMillis() - lastLocalhostAccess;
}
}