// yacyDHTAction.java
// -------------------------------------
// (C) by Michael Peter Christen; mc@anomic.de
// first published on http://www.anomic.de
// Frankfurt, Germany, 2005
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// 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
//
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// by usage of this softare or this documentation. The usage of this software
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package de.anomic.yacy;
import java.util.Enumeration;
import de.anomic.kelondro.kelondroException;
import de.anomic.kelondro.kelondroMScoreCluster;
import de.anomic.server.logging.serverLog;
public class yacyDHTAction implements yacyPeerAction {
private yacySeedDB seedDB;
private kelondroMScoreCluster seedCrawlReady;
public yacyDHTAction(yacySeedDB seedDB) {
this.seedDB = seedDB;
this.seedCrawlReady = new kelondroMScoreCluster();
// init crawl-ready table
try {
Enumeration en = seedDB.seedsConnected(true, false, null);
yacySeed ys;
while (en.hasMoreElements()) {
ys = (yacySeed) en.nextElement();
if ((ys != null) && (ys.getVersion() >= ((float) 0.3))) seedCrawlReady.setScore(ys.hash, yacyCore.yacyTime());
}
} catch (IllegalArgumentException e) {
}
}
public Enumeration getDHTSeeds(boolean up, String firstHash) {
// enumerates seed-type objects: all seeds with starting point in the middle, rotating at the end/beginning
return new seedDHTEnum(up, firstHash);
}
class seedDHTEnum implements Enumeration {
Enumeration e1, e2;
boolean up;
int steps;
public seedDHTEnum(boolean up, String firstHash) {
this.steps = seedDB.sizeConnected();
this.up = up;
this.e1 = seedDB.seedsConnected(up, false, firstHash);
this.e2 = null;
}
public boolean hasMoreElements() {
return (steps > 0) && ((e2 == null) || (e2.hasMoreElements()));
}
public Object nextElement() {
if (steps == 0) return null;
steps--;
if ((e1 != null) && (e1.hasMoreElements())) {
Object n = e1.nextElement();
if (!(e1.hasMoreElements())) {
e1 = null;
e2 = seedDB.seedsConnected(up, false, null);
}
return n;
} else {
if (e2 == null) {
e1 = null;
e2 = seedDB.seedsConnected(up, false, null);
}
return e2.nextElement();
}
}
}
public Enumeration getAcceptRemoteIndexSeeds(String starthash) {
// returns an enumeration of yacySeed-Objects
// that have the AcceptRemoteIndex-Flag set
// the seeds are enumerated in the right order according DHT
return new acceptRemoteIndexSeedEnum(starthash);
}
class acceptRemoteIndexSeedEnum implements Enumeration {
Enumeration se;
yacySeed nextSeed;
public acceptRemoteIndexSeedEnum(String starthash) {
se = getDHTSeeds(true, starthash);
nextSeed = nextInternal();
}
public boolean hasMoreElements() {
return nextSeed != null;
}
private yacySeed nextInternal() {
yacySeed s;
try {
while (se.hasMoreElements()) {
s = (yacySeed) se.nextElement();
if (s == null) return null;
if (s.getFlagAcceptRemoteIndex()) return s;
}
} catch (kelondroException e) {
yacyCore.log.logSevere("database inconsistency (" + e.getMessage() + "), re-set of db.");
seedDB.resetActiveTable();
return null;
}
return null;
}
public Object nextElement() {
yacySeed next = nextSeed;
nextSeed = nextInternal();
return next;
}
}
public Enumeration getAcceptRemoteCrawlSeeds(String starthash, boolean available) {
return new acceptRemoteCrawlSeedEnum(starthash, available);
}
class acceptRemoteCrawlSeedEnum implements Enumeration {
Enumeration se;
yacySeed nextSeed;
boolean available;
public acceptRemoteCrawlSeedEnum(String starthash, boolean available) {
this.se = getDHTSeeds(true, starthash);
this.available = available;
nextSeed = nextInternal();
}
public boolean hasMoreElements() {
return nextSeed != null;
}
private yacySeed nextInternal() {
yacySeed s;
while (se.hasMoreElements()) {
s = (yacySeed) se.nextElement();
if (s == null) return null;
s.available = seedCrawlReady.getScore(s.hash);
if (available) {
if (seedCrawlReady.getScore(s.hash) < yacyCore.yacyTime()) return s;
} else {
if (seedCrawlReady.getScore(s.hash) > yacyCore.yacyTime()) return s;
}
}
return null;
}
public Object nextElement() {
yacySeed next = nextSeed;
nextSeed = nextInternal();
return next;
}
}
public synchronized yacySeed getCrawlSeed(String urlHash) {
Enumeration e = getAcceptRemoteCrawlSeeds(urlHash, true);
yacySeed seed;
if (e.hasMoreElements()) seed = (yacySeed) e.nextElement(); else seed = null;
e = null;
return seed;
}
public void setCrawlTime(String seedHash, int newYacyTime) {
if (newYacyTime < yacyCore.yacyTime()) newYacyTime = yacyCore.yacyTime();
seedCrawlReady.setScore(seedHash, newYacyTime);
}
public void setCrawlDelay(String seedHash, int newDelay) {
seedCrawlReady.setScore(seedHash, yacyCore.yacyTime() + newDelay);
}
public void processPeerArrival(yacySeed peer, boolean direct) {
if (peer.getVersion() >= ((float) 0.3)) {
if (!(seedCrawlReady.existsScore(peer.hash))) seedCrawlReady.setScore(peer.hash, yacyCore.yacyTime());
} else {
seedCrawlReady.deleteScore(peer.hash);
}
}
public void processPeerDeparture(yacySeed peer) {
seedCrawlReady.deleteScore(peer.hash);
}
public void processPeerPing(yacySeed peer) {
}
public static double dhtDistance(String peer, String word) {
// the dht distance is a positive value between 0 and 1
// if the distance is small, the word more probably belongs to the peer
double d = hashDistance(peer, word);
if (d > 0) {
return d; // case where the word is 'before' the peer
} else {
return 1 + d; // wrap-around case
}
}
private static double hashDistance(String from, String to) {
// computes the distance between two hashes.
// the maximum distance between two hashes is 1, the minimum -1
// this can be used like "from - to"
// the result is positive if from > to
if ((from == null) || (to == null) ||
(from.length() == 0) || (to.length() == 0) ||
(from.length() != to.length())) return (double) 0.0;
return hashDistance(from.charAt(0), to.charAt(0)) + hashDistance(from.substring(1), to.substring(1)) / maxAtomarDistance;
}
private static final double maxAtomarDistance = (double) (1+ ((byte) 'z') - ((byte) '-'));
private static double hashDistance(char from, char to) {
// the distance is a little bit fuzzy, since not all characters are used in a hash.
if (from < to)
return -hashDistance(to, from);
else
return ((double) (((byte) from) - ((byte) to))) / maxAtomarDistance;
}
public synchronized yacySeed[] getDHTTargets(serverLog log, int primaryPeerCount, int reservePeerCount, String firstKey, String lastKey, double maxDist) {
// find a list of DHT-peers
yacySeed[] seeds = new yacySeed[primaryPeerCount + reservePeerCount];
int hc0 = 0;
double ownDistance = Math.min(yacyDHTAction.dhtDistance(yacyCore.seedDB.mySeed.hash, firstKey), yacyDHTAction.dhtDistance(yacyCore.seedDB.mySeed.hash, lastKey));
double maxDistance = Math.min(ownDistance, maxDist);
double avdist;
Enumeration e = this.getAcceptRemoteIndexSeeds(lastKey);
while ((e.hasMoreElements()) && (hc0 < seeds.length)) {
seeds[hc0] = (yacySeed) e.nextElement();
if (seeds[hc0] != null) {
avdist = Math.max(yacyDHTAction.dhtDistance(seeds[hc0].hash, firstKey), yacyDHTAction.dhtDistance(seeds[hc0].hash, lastKey));
if (avdist < maxDistance) {
if (log != null) log.logInfo("Selected " + ((hc0 < primaryPeerCount) ? "primary" : "reserve") + " DHT target peer " + seeds[hc0].getName() + ":" + seeds[hc0].hash + ", distance = " + avdist);
hc0++;
}
}
}
e = null; // finish enumeration
if (hc0 == seeds.length) {
return seeds;
} else {
yacySeed[] s = new yacySeed[hc0];
System.arraycopy(seeds, 0, s, 0, hc0);
return s;
}
}
}