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// 
// ========================================================================
// Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// 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.nio.channels.SelectableChannel;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import org.eclipse.jetty.io.SelectorManager;
import org.eclipse.jetty.util.annotation.ManagedAttribute;
import org.eclipse.jetty.util.annotation.ManagedObject;
import org.eclipse.jetty.util.annotation.ManagedOperation;
import org.eclipse.jetty.util.annotation.Name;
import org.eclipse.jetty.util.component.AbstractLifeCycle;
import org.eclipse.jetty.util.component.Container;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.statistic.RateStatistic;
import org.eclipse.jetty.util.thread.Scheduler;

/**
 *  A Listener that limits the rate at which new connections are accepted
 *  
 *  If the limits are exceeded, accepting is suspended until the rate is again below
 *  the limit, so incoming connections are held in the operating system accept
 *  queue (no syn ack sent), where they may either timeout or wait for the server
 *  to resume accepting.
 *  
 *  
 *  It can be applied to an entire server or to a specific connector by adding it
 *  via {@link Container#addBean(Object)}
 *  
 *  
 *  Usage:
 *  
 *   *    Server server = new Server();
 *    server.addBean(new AcceptLimit(100,5,TimeUnit.SECONDS,server));
 *    ...
 *    server.start();
 *  
 *
 *  @see SelectorManager.AcceptListener
 *
 * @deprecated The Eclipse Jetty and Apache Felix Http Jetty packages are no longer supported.
 */
@ManagedObject
@Deprecated(since = "2021-05-27")
public class AcceptRateLimit extends AbstractLifeCycle implements SelectorManager.AcceptListener, Runnable {

    private static final Logger LOG = Log.getLogger(AcceptRateLimit.class);

    private final Server _server;

    private final List _connectors = new ArrayList<>();

    private final Rate _rate;

    private final int _acceptRateLimit;

    private boolean _limiting;

    private Scheduler.Task _task;

    public AcceptRateLimit(@Name("acceptRateLimit") int acceptRateLimit, @Name("period") long period, @Name("units") TimeUnit units, @Name("server") Server server) {
        _server = server;
        _acceptRateLimit = acceptRateLimit;
        _rate = new Rate(period, units);
    }

    public AcceptRateLimit(@Name("limit") int limit, @Name("period") long period, @Name("units") TimeUnit units, @Name("connectors") Connector... connectors) {
        this(limit, period, units, (Server) null);
        for (Connector c : connectors) {
            if (c instanceof AbstractConnector)
                _connectors.add((AbstractConnector) c);
            else
                LOG.warn("Connector {} is not an AbstractConnector. Connections not limited", c);
        }
    }

    @ManagedAttribute("The accept rate limit")
    public int getAcceptRateLimit() {
        return _acceptRateLimit;
    }

    @ManagedAttribute("The accept rate period")
    public long getPeriod() {
        return _rate.getPeriod();
    }

    @ManagedAttribute("The accept rate period units")
    public TimeUnit getUnits() {
        return _rate.getUnits();
    }

    @ManagedAttribute("The current accept rate")
    public int getRate() {
        return _rate.getRate();
    }

    @ManagedAttribute("The maximum accept rate achieved")
    public long getMaxRate() {
        return _rate.getMax();
    }

    @ManagedOperation(value = "Resets the accept rate", impact = "ACTION")
    public void reset() {
        synchronized (_rate) {
            _rate.reset();
            if (_limiting) {
                _limiting = false;
                unlimit();
            }
        }
    }

    protected void age(long period, TimeUnit units) {
        _rate.age(period, units);
    }

    @Override
    protected void doStart() throws Exception {
        synchronized (_rate) {
            if (_server != null) {
                for (Connector c : _server.getConnectors()) {
                    if (c instanceof AbstractConnector)
                        _connectors.add((AbstractConnector) c);
                    else
                        LOG.warn("Connector {} is not an AbstractConnector. Connections not limited", c);
                }
            }
            if (LOG.isDebugEnabled())
                LOG.debug("AcceptLimit accept<{} rate<{} in {} for {}", _acceptRateLimit, _rate, _connectors);
            for (AbstractConnector c : _connectors) {
                c.addBean(this);
            }
        }
    }

    @Override
    protected void doStop() throws Exception {
        synchronized (_rate) {
            if (_task != null)
                _task.cancel();
            _task = null;
            for (AbstractConnector c : _connectors) {
                c.removeBean(this);
            }
            if (_server != null)
                _connectors.clear();
            _limiting = false;
        }
    }

    protected void limit() {
        for (AbstractConnector c : _connectors) {
            c.setAccepting(false);
        }
        schedule();
    }

    protected void unlimit() {
        for (AbstractConnector c : _connectors) {
            c.setAccepting(true);
        }
    }

    @Override
    public void onAccepting(SelectableChannel channel) {
        synchronized (_rate) {
            int rate = _rate.record();
            if (LOG.isDebugEnabled()) {
                LOG.debug("onAccepting rate {}/{} for {} {}", rate, _acceptRateLimit, _rate, channel);
            }
            if (rate > _acceptRateLimit) {
                if (!_limiting) {
                    _limiting = true;
                    LOG.warn("AcceptLimit rate exceeded {}>{} on {}", rate, _acceptRateLimit, _connectors);
                    limit();
                }
            }
        }
    }

    private void schedule() {
        long oldest = _rate.getOldest(TimeUnit.MILLISECONDS);
        long period = TimeUnit.MILLISECONDS.convert(_rate.getPeriod(), _rate.getUnits());
        long delay = period - (oldest > 0 ? oldest : 0);
        if (delay < 0)
            delay = 0;
        if (LOG.isDebugEnabled())
            LOG.debug("schedule {} {}", delay, TimeUnit.MILLISECONDS);
        _task = _connectors.get(0).getScheduler().schedule(this, delay, TimeUnit.MILLISECONDS);
    }

    @Override
    public void run() {
        synchronized (_rate) {
            _task = null;
            if (!isRunning())
                return;
            int rate = _rate.getRate();
            if (rate > _acceptRateLimit) {
                schedule();
                return;
            }
            if (_limiting) {
                _limiting = false;
                LOG.warn("AcceptLimit rate OK {}<={} on {}", rate, _acceptRateLimit, _connectors);
                unlimit();
            }
        }
    }

    // @deprecated The Eclipse Jetty and Apache Felix Http Jetty packages are no longer supported.
    @Deprecated(since = "2021-05-27")
    private final class Rate extends RateStatistic {

        private Rate(long period, TimeUnit units) {
            super(period, units);
        }

        @Override
        protected void age(long period, TimeUnit units) {
            super.age(period, units);
        }
    }
}