//
// ========================================================================
// Copyright (c) 1995-2014 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 com.facebook.presto.jdbc.internal.jetty.util;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.channels.UnresolvedAddressException;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import com.facebook.presto.jdbc.internal.jetty.util.log.Log;
import com.facebook.presto.jdbc.internal.jetty.util.log.Logger;
import com.facebook.presto.jdbc.internal.jetty.util.thread.Scheduler;
/**
* Creates asynchronously {@link SocketAddress} instances, returning them through a {@link Promise},
* in order to avoid blocking on DNS lookup.
* <p />
* {@link InetSocketAddress#InetSocketAddress(String, int)} attempts to perform a DNS resolution of
* the host name, and this may block for several seconds.
* This class creates the {@link InetSocketAddress} in a separate thread and provides the result
* through a {@link Promise}, with the possibility to specify a timeout for the operation.
* <p />
* Example usage:
* <pre>
* SocketAddressResolver resolver = new SocketAddressResolver(executor, scheduler);
* resolver.resolve("www.google.com", 80, new Promise<SocketAddress>()
* {
* public void succeeded(SocketAddress result)
* {
* // The address was resolved
* }
*
* public void failed(Throwable failure)
* {
* // The address resolution failed
* }
* });
* </pre>
*/
public class SocketAddressResolver
{
private static final Logger LOG = Log.getLogger(SocketAddressResolver.class);
private final Executor executor;
private final Scheduler scheduler;
private final long timeout;
/**
* Creates a new instance with the given executor (to perform DNS resolution in a separate thread),
* the given scheduler (to cancel the operation if it takes too long) and the given timeout, in milliseconds.
*
* @param executor the thread pool to use to perform DNS resolution in pooled threads
* @param scheduler the scheduler to schedule tasks to cancel DNS resolution if it takes too long
* @param timeout the timeout, in milliseconds, for the DNS resolution to complete
*/
public SocketAddressResolver(Executor executor, Scheduler scheduler, long timeout)
{
this.executor = executor;
this.scheduler = scheduler;
this.timeout = timeout;
}
public Executor getExecutor()
{
return executor;
}
public Scheduler getScheduler()
{
return scheduler;
}
public long getTimeout()
{
return timeout;
}
/**
* Resolves the given host and port, returning a {@link SocketAddress} through the given {@link Promise}
* with the default timeout.
*
* @param host the host to resolve
* @param port the port of the resulting socket address
* @param promise the callback invoked when the resolution succeeds or fails
* @see #resolve(String, int, long, Promise)
*/
public void resolve(String host, int port, Promise<SocketAddress> promise)
{
resolve(host, port, timeout, promise);
}
/**
* Resolves the given host and port, returning a {@link SocketAddress} through the given {@link Promise}
* with the given timeout.
*
* @param host the host to resolve
* @param port the port of the resulting socket address
* @param timeout the timeout, in milliseconds, for the DNS resolution to complete
* @param promise the callback invoked when the resolution succeeds or fails
*/
protected void resolve(final String host, final int port, final long timeout, final Promise<SocketAddress> promise)
{
executor.execute(new Runnable()
{
@Override
public void run()
{
Scheduler.Task task = null;
final AtomicBoolean complete = new AtomicBoolean();
if (timeout > 0)
{
final Thread thread = Thread.currentThread();
task = scheduler.schedule(new Runnable()
{
@Override
public void run()
{
if (complete.compareAndSet(false, true))
{
promise.failed(new TimeoutException());
thread.interrupt();
}
}
}, timeout, TimeUnit.MILLISECONDS);
}
try
{
long start = System.nanoTime();
InetSocketAddress result = new InetSocketAddress(host, port);
long elapsed = System.nanoTime() - start;
LOG.debug("Resolved {} in {} ms", host, TimeUnit.NANOSECONDS.toMillis(elapsed));
if (complete.compareAndSet(false, true))
{
if (result.isUnresolved())
promise.failed(new UnresolvedAddressException());
else
promise.succeeded(result);
}
}
catch (Throwable x)
{
if (complete.compareAndSet(false, true))
promise.failed(x);
}
finally
{
if (task != null)
task.cancel();
// Reset the interrupted status before releasing the thread to the pool
Thread.interrupted();
}
}
});
}
}