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A-Jetty Base can run on Android Java as well as on standard Java 7+ and it can run precompiled JSP/JSTL.
//
// ========================================================================
// Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.server;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.eclipse.jetty.io.EndPoint;
import org.eclipse.jetty.util.annotation.ManagedAttribute;
import org.eclipse.jetty.util.annotation.ManagedObject;
import org.eclipse.jetty.util.annotation.Name;
import org.eclipse.jetty.util.component.AbstractLifeCycle;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.thread.ScheduledExecutorScheduler;
import org.eclipse.jetty.util.thread.Scheduler;
import org.eclipse.jetty.util.thread.ThreadPool;
/* ------------------------------------------------------------ */
/** A monitor for low resources
* An instance of this class will monitor all the connectors of a server (or a set of connectors
* configured with {@link #setMonitoredConnectors(Collection)}) for a low resources state.
* Low resources can be detected by:
* - {@link ThreadPool#isLowOnThreads()} if {@link Connector#getExecutor()} is
* an instance of {@link ThreadPool} and {@link #setMonitorThreads(boolean)} is true.
-
*
- If {@link #setMaxMemory(long)} is non zero then low resources is detected if the JVMs
* {@link Runtime} instance has {@link Runtime#totalMemory()} minus {@link Runtime#freeMemory()}
* greater than {@link #getMaxMemory()}
* - If {@link #setMaxConnections(int)} is non zero then low resources is dected if the total number
* of connections exceeds {@link #getMaxConnections()}
*
*
* Once low resources state is detected, the cause is logged and all existing connections returned
* by {@link Connector#getConnectedEndPoints()} have {@link EndPoint#setIdleTimeout(long)} set
* to {@link #getLowResourcesIdleTimeout()}. New connections are not affected, however if the low
* resources state persists for more than {@link #getMaxLowResourcesTime()}, then the
* {@link #getLowResourcesIdleTimeout()} to all connections again. Once the low resources state is
* cleared, the idle timeout is reset to the connector default given by {@link Connector#getIdleTimeout()}.
*
*/
@ManagedObject ("Monitor for low resource conditions and activate a low resource mode if detected")
public class LowResourceMonitor extends AbstractLifeCycle
{
private static final Logger LOG = Log.getLogger(LowResourceMonitor.class);
private final Server _server;
private Scheduler _scheduler;
private Connector[] _monitoredConnectors;
private int _period=1000;
private int _maxConnections;
private long _maxMemory;
private int _lowResourcesIdleTimeout=1000;
private int _maxLowResourcesTime=0;
private boolean _monitorThreads=true;
private final AtomicBoolean _low = new AtomicBoolean();
private String _cause;
private String _reasons;
private long _lowStarted;
private final Runnable _monitor = new Runnable()
{
@Override
public void run()
{
if (isRunning())
{
monitor();
_scheduler.schedule(_monitor,_period,TimeUnit.MILLISECONDS);
}
}
};
public LowResourceMonitor(@Name("server") Server server)
{
_server=server;
}
@ManagedAttribute("Are the monitored connectors low on resources?")
public boolean isLowOnResources()
{
return _low.get();
}
@ManagedAttribute("The reason(s) the monitored connectors are low on resources")
public String getLowResourcesReasons()
{
return _reasons;
}
@ManagedAttribute("Get the timestamp in ms since epoch that low resources state started")
public long getLowResourcesStarted()
{
return _lowStarted;
}
@ManagedAttribute("The monitored connectors. If null then all server connectors are monitored")
public Collection getMonitoredConnectors()
{
if (_monitoredConnectors==null)
return Collections.emptyList();
return Arrays.asList(_monitoredConnectors);
}
/**
* @param monitoredConnectors The collections of Connectors that should be monitored for low resources.
*/
public void setMonitoredConnectors(Collection monitoredConnectors)
{
if (monitoredConnectors==null || monitoredConnectors.size()==0)
_monitoredConnectors=null;
else
_monitoredConnectors = monitoredConnectors.toArray(new Connector[monitoredConnectors.size()]);
}
@ManagedAttribute("The monitor period in ms")
public int getPeriod()
{
return _period;
}
/**
* @param periodMS The period in ms to monitor for low resources
*/
public void setPeriod(int periodMS)
{
_period = periodMS;
}
@ManagedAttribute("True if low available threads status is monitored")
public boolean getMonitorThreads()
{
return _monitorThreads;
}
/**
* @param monitorThreads If true, check connectors executors to see if they are
* {@link ThreadPool} instances that are low on threads.
*/
public void setMonitorThreads(boolean monitorThreads)
{
_monitorThreads = monitorThreads;
}
@ManagedAttribute("The maximum connections allowed for the monitored connectors before low resource handling is activated")
public int getMaxConnections()
{
return _maxConnections;
}
/**
* @param maxConnections The maximum connections before low resources state is triggered
*/
public void setMaxConnections(int maxConnections)
{
_maxConnections = maxConnections;
}
@ManagedAttribute("The maximum memory (in bytes) that can be used before low resources is triggered. Memory used is calculated as (totalMemory-freeMemory).")
public long getMaxMemory()
{
return _maxMemory;
}
/**
* @param maxMemoryBytes The maximum memory in bytes in use before low resources is triggered.
*/
public void setMaxMemory(long maxMemoryBytes)
{
_maxMemory = maxMemoryBytes;
}
@ManagedAttribute("The idletimeout in ms to apply to all existing connections when low resources is detected")
public int getLowResourcesIdleTimeout()
{
return _lowResourcesIdleTimeout;
}
/**
* @param lowResourcesIdleTimeoutMS The timeout in ms to apply to EndPoints when in the low resources state.
*/
public void setLowResourcesIdleTimeout(int lowResourcesIdleTimeoutMS)
{
_lowResourcesIdleTimeout = lowResourcesIdleTimeoutMS;
}
@ManagedAttribute("The maximum time in ms that low resources condition can persist before lowResourcesIdleTimeout is applied to new connections as well as existing connections")
public int getMaxLowResourcesTime()
{
return _maxLowResourcesTime;
}
/**
* @param maxLowResourcesTimeMS The time in milliseconds that a low resource state can persist before the low resource idle timeout is reapplied to all connections
*/
public void setMaxLowResourcesTime(int maxLowResourcesTimeMS)
{
_maxLowResourcesTime = maxLowResourcesTimeMS;
}
@Override
protected void doStart() throws Exception
{
_scheduler = _server.getBean(Scheduler.class);
if (_scheduler==null)
{
_scheduler=new LRMScheduler();
_scheduler.start();
}
super.doStart();
_scheduler.schedule(_monitor,_period,TimeUnit.MILLISECONDS);
}
@Override
protected void doStop() throws Exception
{
if (_scheduler instanceof LRMScheduler)
_scheduler.stop();
super.doStop();
}
protected Connector[] getMonitoredOrServerConnectors()
{
if (_monitoredConnectors!=null && _monitoredConnectors.length>0)
return _monitoredConnectors;
return _server.getConnectors();
}
protected void monitor()
{
String reasons=null;
String cause="";
int connections=0;
for(Connector connector : getMonitoredOrServerConnectors())
{
connections+=connector.getConnectedEndPoints().size();
Executor executor = connector.getExecutor();
if (executor instanceof ThreadPool)
{
ThreadPool threadpool=(ThreadPool) executor;
if (_monitorThreads && threadpool.isLowOnThreads())
{
reasons=low(reasons,"Low on threads: "+threadpool);
cause+="T";
}
}
}
if (_maxConnections>0 && connections>_maxConnections)
{
reasons=low(reasons,"Max Connections exceeded: "+connections+">"+_maxConnections);
cause+="C";
}
long memory=Runtime.getRuntime().totalMemory()-Runtime.getRuntime().freeMemory();
if (_maxMemory>0 && memory>_maxMemory)
{
reasons=low(reasons,"Max memory exceeded: "+memory+">"+_maxMemory);
cause+="M";
}
if (reasons!=null)
{
// Log the reasons if there is any change in the cause
if (!cause.equals(_cause))
{
LOG.warn("Low Resources: {}",reasons);
_cause=cause;
}
// Enter low resources state?
if (_low.compareAndSet(false,true))
{
_reasons=reasons;
_lowStarted=System.currentTimeMillis();
setLowResources();
}
// Too long in low resources state?
if (_maxLowResourcesTime>0 && (System.currentTimeMillis()-_lowStarted)>_maxLowResourcesTime)
setLowResources();
}
else
{
if (_low.compareAndSet(true,false))
{
LOG.info("Low Resources cleared");
_reasons=null;
_lowStarted=0;
_cause=null;
clearLowResources();
}
}
}
protected void setLowResources()
{
for(Connector connector : getMonitoredOrServerConnectors())
{
for (EndPoint endPoint : connector.getConnectedEndPoints())
endPoint.setIdleTimeout(_lowResourcesIdleTimeout);
}
}
protected void clearLowResources()
{
for(Connector connector : getMonitoredOrServerConnectors())
{
for (EndPoint endPoint : connector.getConnectedEndPoints())
endPoint.setIdleTimeout(connector.getIdleTimeout());
}
}
private String low(String reasons, String newReason)
{
if (reasons==null)
return newReason;
return reasons+", "+newReason;
}
private static class LRMScheduler extends ScheduledExecutorScheduler
{
}
}