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Utility classes for Jetty
//
// ========================================================================
// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//
package org.eclipse.jetty.util.component;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.AtomicReference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Jetty components that wish to be part of a Graceful shutdown implement this interface so that
* the {@link Graceful#shutdown()} method will be called to initiate a shutdown. Shutdown operations
* can fall into the following categories:
*
* - Preventing new load from being accepted (eg connectors stop accepting connections)
* - Preventing existing load expanding (eg stopping existing connections accepting new requests)
* - Waiting for existing load to complete (eg waiting for active request count to reduce to 0)
* - Performing cleanup operations that may take time (eg closing an SSL connection)
*
* The {@link CompletableFuture} returned by the the shutdown call will be completed to indicate the
* shutdown operation is completed.
* Some shutdown operations may be instantaneous and always return a completed future.
*
* Graceful shutdown is typically orchestrated by the doStop methods of Server or ContextHandler (for a full or partial
* shutdown respectively).
*
*/
public interface Graceful
{
/**
* Shutdown the component. When this method returns, the component should not accept any new load.
* @return A future that is completed once all load on the component is completed
*/
CompletableFuture shutdown();
/**
* @return True if {@link #shutdown()} has been called.
*/
boolean isShutdown();
/**
* A utility class to assist implementing the Graceful interface.
* The {@link #isShutdownDone()} method should be implemented to check if the {@link CompletableFuture}
* returned by {@link #shutdown()} should be completed or not. The {@link #check()}
* method should be called when any state is changed which may complete the shutdown.
*/
abstract class Shutdown implements Graceful
{
final Object _component;
final AtomicReference> _done = new AtomicReference<>();
protected Shutdown(Object component)
{
_component = component;
}
@Override
public CompletableFuture shutdown()
{
if (_done.get() == null)
{
_done.compareAndSet(null, new CompletableFuture<>()
{
@Override
public String toString()
{
return String.format("Shutdown<%s>@%x", _component, hashCode());
}
});
}
CompletableFuture done = _done.get();
check();
return done;
}
@Override
public boolean isShutdown()
{
return _done.get() != null;
}
/**
* This method should be called whenever the components state has been updated.
* If {@link #shutdown()} has been called, then {@link #isShutdownDone()} is called
* by this method and if it returns true then the {@link Future} returned by
* {@link #shutdown()} is completed.
*/
public void check()
{
CompletableFuture done = _done.get();
if (done != null && isShutdownDone())
done.complete(null);
}
public void cancel()
{
CompletableFuture done = _done.get();
if (done != null && !done.isDone())
done.cancel(true);
_done.set(null);
}
/**
* @return True if the component is shutdown and has no remaining load.
*/
public abstract boolean isShutdownDone();
}
/**
* Utility method to shutdown all Gracefuls within a container.
* @param component The container in which to look for {@link Graceful}s
* @return A {@link CompletableFuture } that is complete once all returns from {@link Graceful#shutdown()}
* of the contained {@link Graceful}s are complete.
*/
static CompletableFuture shutdown(Container component)
{
Logger log = LoggerFactory.getLogger(component.getClass());
log.info("Shutdown {}", component);
// tell the graceful handlers that we are shutting down
List gracefuls = new ArrayList<>();
if (component instanceof Graceful)
gracefuls.add((Graceful)component);
gracefuls.addAll(component.getContainedBeans(Graceful.class));
if (log.isDebugEnabled())
gracefuls.forEach(g -> log.debug("graceful {}", g));
return CompletableFuture.allOf(gracefuls.stream().map(Graceful::shutdown).toArray(CompletableFuture[]::new));
}
/**
* Utility method to execute a {@link ThrowingRunnable} in a new daemon thread and
* be notified of the result in a {@link CompletableFuture}.
* @param runnable the ThrowingRunnable to run.
* @return the CompletableFuture to be notified when the runnable either completes or fails.
*/
static CompletableFuture shutdown(ThrowingRunnable runnable)
{
AtomicReference stopThreadReference = new AtomicReference<>();
CompletableFuture shutdown = new CompletableFuture<>()
{
@Override
public boolean cancel(boolean mayInterruptIfRunning)
{
boolean canceled = super.cancel(mayInterruptIfRunning);
if (canceled && mayInterruptIfRunning)
{
Thread thread = stopThreadReference.get();
if (thread != null)
thread.interrupt();
}
return canceled;
}
};
Thread stopThread = new Thread(() ->
{
try
{
runnable.run();
shutdown.complete(null);
}
catch (Throwable t)
{
shutdown.completeExceptionally(t);
}
});
stopThread.setDaemon(true);
stopThreadReference.set(stopThread);
stopThread.start();
return shutdown;
}
@FunctionalInterface
interface ThrowingRunnable
{
void run() throws Exception;
}
}