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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 java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.eclipse.jetty.client.api.Connection;
import org.eclipse.jetty.client.api.Destination;
import org.eclipse.jetty.util.Callback;
import org.eclipse.jetty.util.annotation.ManagedAttribute;
import org.eclipse.jetty.util.component.Dumpable;
import org.eclipse.jetty.util.component.DumpableCollection;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.thread.Scheduler;

/**
 *  A connection pool that validates connections before
 *  making them available for use.
 *  Connections that have just been opened are not validated.
 *  Connections that are {@link #release(Connection) released} will
 *  be validated.
 *  Validation by reading from the EndPoint is not reliable,
 *  since the TCP FIN may arrive just after the validation read.
 *  This class validates connections by putting them in a
 *  "quarantine" for a configurable timeout, where they cannot
 *  be used to send requests. When the timeout expires, the
 *  quarantined connection is made idle and therefore available
 *  to send requests.
 *  The existing HttpClient mechanism to detect server closes
 *  will trigger and close quarantined connections, before they
 *  are made idle (and reusable) again.
 *  There still is a small chance that the timeout expires,
 *  the connection is made idle and available again, it is used
 *  to send a request exactly when the server decides to close.
 *  This case is however unavoidable and may be mitigated by
 *  tuning the idle timeout of the servers to be larger than
 *  that of the client.
 *
 * @deprecated The Eclipse Jetty and Apache Felix Http Jetty packages are no longer supported.
 */
@Deprecated(since = "2021-05-27")
public class ValidatingConnectionPool extends DuplexConnectionPool {

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

    private final Scheduler scheduler;

    private final long timeout;

    private final Map quarantine;

    public ValidatingConnectionPool(Destination destination, int maxConnections, Callback requester, Scheduler scheduler, long timeout) {
        super((HttpDestination) destination, maxConnections, requester);
        this.scheduler = scheduler;
        this.timeout = timeout;
        this.quarantine = new ConcurrentHashMap<>(maxConnections);
    }

    @ManagedAttribute(value = "The number of validating connections", readonly = true)
    public int getValidatingConnectionCount() {
        return quarantine.size();
    }

    @Override
    public boolean release(Connection connection) {
        Holder holder = new Holder(connection);
        holder.task = scheduler.schedule(holder, timeout, TimeUnit.MILLISECONDS);
        quarantine.put(connection, holder);
        if (LOG.isDebugEnabled())
            LOG.debug("Validating for {}ms {}", timeout, connection);
        released(connection);
        return true;
    }

    @Override
    public boolean remove(Connection connection) {
        Holder holder = quarantine.remove(connection);
        if (holder == null)
            return super.remove(connection);
        if (LOG.isDebugEnabled())
            LOG.debug("Removed while validating {}", connection);
        boolean cancelled = holder.cancel();
        if (cancelled)
            return remove(connection, true);
        return super.remove(connection);
    }

    @Override
    public void dump(Appendable out, String indent) throws IOException {
        DumpableCollection toDump = new DumpableCollection("quarantine", quarantine.values());
        Dumpable.dumpObjects(out, indent, this, toDump);
    }

    @Override
    public String toString() {
        int size = quarantine.size();
        return String.format("%s[v=%d]", super.toString(), size);
    }

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

        private final long timestamp = System.nanoTime();

        private final AtomicBoolean done = new AtomicBoolean();

        private final Connection connection;

        public Scheduler.Task task;

        public Holder(Connection connection) {
            this.connection = connection;
        }

        @Override
        public void run() {
            if (done.compareAndSet(false, true)) {
                boolean closed = isClosed();
                if (LOG.isDebugEnabled())
                    LOG.debug("Validated {}", connection);
                quarantine.remove(connection);
                if (!closed)
                    deactivate(connection);
                idle(connection, closed);
                proceed();
            }
        }

        public boolean cancel() {
            if (done.compareAndSet(false, true)) {
                task.cancel();
                return true;
            }
            return false;
        }

        @Override
        public String toString() {
            return String.format("%s[validationLeft=%dms]", connection, timeout - TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - timestamp));
        }
    }
}