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//
// ========================================================================
// Copyright (c) 1995-2015 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.client;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
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.ContainerLifeCycle;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.thread.Scheduler;
/**
* <p>A connection pool that validates connections before
* making them available for use.</p>
* <p>Connections that have just been opened are not validated.
* Connections that are {@link #release(Connection) released} will
* be validated.</p>
* <p>Validation by reading from the EndPoint is not reliable,
* since the TCP FIN may arrive just after the validation read.</p>
* <p>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.</p>
* <p>The existing HttpClient mechanism to detect server closes
* will trigger and close quarantined connections, before they
* are made idle (and reusable) again.</p>
* <p>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.</p>
*/
public class ValidatingConnectionPool extends ConnectionPool
{
private static final Logger LOG = Log.getLogger(ValidatingConnectionPool.class);
private final Scheduler scheduler;
private final long timeout;
private final Map<Connection, Holder> quarantine;
public ValidatingConnectionPool(Destination destination, int maxConnections, Callback requester, Scheduler scheduler, long timeout)
{
super(destination, maxConnections, requester);
this.scheduler = scheduler;
this.timeout = timeout;
this.quarantine = new HashMap<>(maxConnections);
}
@ManagedAttribute(value = "The number of validating connections", readonly = true)
public int getValidatingConnectionCount()
{
return quarantine.size();
}
@Override
public boolean release(Connection connection)
{
lock();
try
{
if (!getActiveConnections().remove(connection))
return false;
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);
}
finally
{
unlock();
}
released(connection);
return true;
}
@Override
public boolean remove(Connection connection)
{
Holder holder;
lock();
try
{
holder = quarantine.remove(connection);
}
finally
{
unlock();
}
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
{
super.dump(out, indent);
ContainerLifeCycle.dump(out, indent, quarantine.values());
}
@Override
public String toString()
{
int size;
lock();
try
{
size = quarantine.size();
}
finally
{
unlock();
}
return String.format("%s[v=%d]", super.toString(), size);
}
private class Holder implements Runnable
{
private final long timestamp = System.nanoTime();
private final AtomicBoolean latch = new AtomicBoolean();
private final Connection connection;
public Scheduler.Task task;
public Holder(Connection connection)
{
this.connection = connection;
}
@Override
public void run()
{
if (latch.compareAndSet(false, true))
{
boolean idle;
lock();
try
{
quarantine.remove(connection);
idle = offerIdle(connection);
if (LOG.isDebugEnabled())
LOG.debug("Validated {}", connection);
}
finally
{
unlock();
}
if (idle(connection, idle))
proceed();
}
}
public boolean cancel()
{
if (latch.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)
);
}
}
}
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