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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.client;

import org.eclipse.jetty.util.Callback;
import org.eclipse.jetty.util.Pool;
import org.eclipse.jetty.util.annotation.ManagedObject;

/**
 *  A {@link ConnectionPool} that attempts to provide connections using a round-robin algorithm.
 *  The round-robin behavior is almost impossible to achieve for several reasons:
 *  
 *      the server takes different times to serve different requests; if a request takes a long
 *      time to be processed by the server, it would be a performance penalty to stall sending requests
 *      waiting for that connection to be available - better skip it and try another connection
 *      connections may be closed by the client or by the server, so it would be a performance
 *      penalty to stall sending requests waiting for a new connection to be opened
 *      thread scheduling on both client and server may temporarily penalize a connection
 *  
 *  Do not expect this class to provide connections in a perfect recurring sequence such as
 *  {@code c0, c1, ..., cN-1, c0, c1, ..., cN-1, c0, c1, ...} because that is impossible to
 *  achieve in a real environment.
 *  This class will just attempt a best-effort to provide the connections in a sequential order,
 *  but most likely the order will be quasi-random.
 *  Applications using this class should {@link #preCreateConnections(int) pre-create}
 *  the connections to ensure that they are already opened when the application starts to requests
 *  them, otherwise the first connection that is opened may be used multiple times before the others
 *  are opened, resulting in a behavior that is more random-like than more round-robin-like (and
 *  that confirms that round-robin behavior is almost impossible to achieve).
 *
 *  @see RandomConnectionPool
 *
 * @deprecated The Eclipse Jetty and Apache Felix Http Jetty packages are no longer supported.
 */
@ManagedObject
@Deprecated(since = "2021-05-27")
public class RoundRobinConnectionPool extends MultiplexConnectionPool {

    public RoundRobinConnectionPool(HttpDestination destination, int maxConnections, Callback requester) {
        this(destination, maxConnections, requester, 1);
    }

    public RoundRobinConnectionPool(HttpDestination destination, int maxConnections, Callback requester, int maxMultiplex) {
        super(destination, Pool.StrategyType.ROUND_ROBIN, maxConnections, false, requester, maxMultiplex);
        // If there are queued requests and connections get
        // closed due to idle timeout or overuse, we want to
        // aggressively try to open new connections to replace
        // those that were closed to process queued requests.
        setMaximizeConnections(true);
    }
}