/*
* Created on Jul 28, 2004
* Created by Alon Rohter
* Copyright (C) 2004, 2005, 2006 Aelitis, All Rights Reserved.
*
* 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.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
*
*/
package com.aelitis.azureus.core.networkmanager.impl.tcp;
import org.gudy.azureus2.core3.logging.*;
import org.gudy.azureus2.core3.util.*;
/**
* Temp class designed to help detect Selector anomalies and cleanly re-open if necessary.
*
* NOTE:
* As of JVM 1.4.2_03, after network connection disconnect/reconnect, usually-blocking
* select() and select(long) calls no longer block, and will instead return immediately.
* This can cause selector spinning and 100% cpu usage.
* See:
* http://forum.java.sun.com/thread.jsp?forum=4&thread=293213
* http://developer.java.sun.com/developer/bugParade/bugs/4850373.html
* http://developer.java.sun.com/developer/bugParade/bugs/4881228.html
* Fixed in JVM 1.4.2_05+ and 1.5b2+
*/
public class SelectorGuard {
private static final int SELECTOR_SPIN_THRESHOLD = 200;
private static final int SELECTOR_FAILURE_THRESHOLD = 10000;
private static final int MAX_IGNORES = 5;
private boolean marked = false;
private int consecutiveZeroSelects = 0;
private long beforeSelectTime;
private long select_op_time;
private final String type;
private final GuardListener listener;
private int ignores = 0;
/**
* Create a new SelectorGuard with the given failed count threshold.
*/
public SelectorGuard( String _type, GuardListener _listener ) {
this.type = _type;
this.listener = _listener;
}
public String
getType()
{
return( type );
}
/**
* Run this method right before the select() operation to
* mark the start time.
*/
public void markPreSelectTime() {
beforeSelectTime = SystemTime.getCurrentTime();
marked = true;
}
/**
* Checks whether selector is still OK, and not spinning.
*/
public void verifySelectorIntegrity( int num_keys_ready, long time_threshold ) {
if( num_keys_ready > 0 ) { //non-zero select, so OK
ignores++;
if( ignores > MAX_IGNORES ) { //allow MAX_IGNORES / SELECTOR_SPIN_THRESHOLD to be successful select ops and still trigger a spin alert
ignores = 0;
consecutiveZeroSelects = 0;
}
return;
}
if (marked) marked = false;
else Debug.out("Error: You must run markPreSelectTime() before calling isSelectorOK");
select_op_time = SystemTime.getCurrentTime() - beforeSelectTime;
if( select_op_time > time_threshold || select_op_time < 0 ) {
//zero-select, but over the time threshold, so OK
consecutiveZeroSelects = 0;
return;
}
//if we've gotten here, then we have a potential selector anomalie
consecutiveZeroSelects++;
if( consecutiveZeroSelects % 20 == 0 && Constants.isWindows ) {
// getting triggered with 20 +_ sometimes 40 due to general high CPU usage
if ( consecutiveZeroSelects > 40 ){
Debug.out( "consecutiveZeroSelects=" +consecutiveZeroSelects );
}
}
if( consecutiveZeroSelects > SELECTOR_SPIN_THRESHOLD ) {
if( Constants.isWindows && (Constants.JAVA_VERSION.startsWith("1.4") || Constants.JAVA_VERSION.startsWith("1.5"))) {
//Under windows, it seems that selector spin can sometimes appear when >63 socket channels are registered with a selector
//Should be fixed in later 1.5, but play it safe and assume 1.6 or newer only.
if( !listener.safeModeSelectEnabled() ) {
String msg = "Likely faulty socket selector detected: reverting to safe-mode socket selection. [JRE " +Constants.JAVA_VERSION+"]\n";
msg += "Please see " +Constants.AZUREUS_WIKI+ "LikelyFaultySocketSelector for help.";
Debug.out( msg );
Logger.log(new LogAlert(LogAlert.UNREPEATABLE, LogAlert.AT_WARNING, msg));
consecutiveZeroSelects = 0;
listener.spinDetected();
return;
}
}
else {
//under linux, it seems that selector spin is somewhat common, but normal??? behavior, so just sleep a bit
consecutiveZeroSelects = 0;
try{ Thread.sleep( 50 ); }catch( Throwable t) {t.printStackTrace();}
return;
}
}
if( consecutiveZeroSelects > SELECTOR_FAILURE_THRESHOLD ) { //should only happen under Windows + JRE 1.4
String msg = "Likely network disconnect/reconnect: Repairing socket channel selector. [JRE " +Constants.JAVA_VERSION+"]\n";
msg += "Please see " +Constants.AZUREUS_WIKI+ "LikelyNetworkDisconnectReconnect for help.";
Debug.out( msg );
Logger.log(new LogAlert(LogAlert.UNREPEATABLE, LogAlert.AT_WARNING, msg));
consecutiveZeroSelects = 0;
listener.failureDetected();
return;
}
//not yet over the count threshold
}
public interface GuardListener {
public boolean safeModeSelectEnabled();
public void spinDetected();
public void failureDetected();
}
}
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