io.baratine.pipe.Credits Maven / Gradle / Ivy
Show all versions of api Show documentation
/*
* Copyright (c) 1998-2015 Caucho Technology -- all rights reserved
*
* This file is part of Baratine(TM)(TM)
*
* Each copy or derived work must preserve the copyright notice and this
* notice unmodified.
*
* Baratine is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Baratine is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
* of NON-INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with Baratine; if not, write to the
*
* Free Software Foundation, Inc.
* 59 Temple Place, Suite 330
* Boston, MA 02111-1307 USA
*
* @author Scott Ferguson
*/
package io.baratine.pipe;
import java.util.concurrent.TimeUnit;
import io.baratine.service.Cancel;
/**
* {@code Credits} controls message flow. The methods on this interface are used
* to let the publisher know when consumer is able to accept more messages.
*
* This is achieved by giving credits to the publisher. The publisher should
* read the credits value and make sure it's greater than 0 before attempting
* to send a next message.
*
*
* Example below provides simplified code which demonstrates concept of granting
* credits. Production code should subscribe to Credits with OnAvailable callback
* for proper implementation.
*
*
*
* public class TestPipesQuotes
* {
* @Inject
* Services _services;
*
* public void quotes() throws InterruptedException
* {
* QuoteServer server = _services.newService(QuoteServer.class)
* .auto()
* .as(QuoteServer.class);
*
* QuoteClient client = _services.newService(QuoteClient.class)
* .auto()
* .start()
* .as(QuoteClient.class);
*
* State.sleep(100); //give time for pipe to connect subscriber and consumer
* server.newQuote("MARS 9.99"); //send the first quote. It will come through
* // and use up the only available credit
*
* server.newQuote("MARS 9.98"); //send second quote. It will be ignored
* //by the if statement in newQuote() because
* //available credits is 0 at this point
* Thread.sleep(100);
*
* client.addCredit(1); //adds a credit
* Thread.sleep(10); //time for credits to propagate
*
* server.newQuote("MARS 9.97"); //send another quote which should now come through
*
* State.sleep(1000);
* }
*
* @Service
* public static class QuoteClient
* {
* private Credits _credits;
*
* @OnInit
* public void init()
* {
* PipeSub<String> subscriber = PipeSub.of(this::onMessage)
* .prefetch(0)
* .credits(1)
* .credits(c -> {
* _credits = c;
* });
*
* Services services = Services.current();
*
* QuoteServer server = services.service(QuoteServer.class);
*
* server.connect(subscriber);
* }
*
* public void addCredit(int credits)
* {
* _credits.add(credits);
* }
*
* private void onMessage(String message)
* {
* System.out.println("new quote: " + message);
* }
* }
*
* @Service
* public static class QuoteServer
* {
* private Pipe<String> _quotes;
* private Credits _credits;
*
* public void connect(PipeSub<String> subscription)
* {
* _quotes = subscription.pipe();
* _credits = _quotes.credits();
*
* subscription.ok(null);
* }
*
* public void newQuote(String quote)
* {
* if (_credits != null && _credits.available() > 0) {
* _quotes.next(quote);
* }
* }
* }
* }
*
*
*/
public interface Credits extends Cancel
{
/**
* Returns a long representing current sequence value
*
* @return current credit sequence value
*/
long get();
/**
* Returns a number of messages client can accept.
*
* @return number of messages client can accept
*/
int available();
/**
* Sets the new credit sequence when prefetch is disabled. Used by
* applications that need finer control.
*
* Applications using credit need to continually add credits.
*
* @param creditSequence next credit in the sequence
* @throws IllegalStateException if prefetch is used
*/
default void set(long creditSequence)
{
throw new UnsupportedOperationException(getClass().getName());
}
/**
* Adds credits.
*
* Convenience method based on the {@code credits} methods.
*
* @param newCredits number of credits to add
*/
default void add(int newCredits)
{
set(get() + newCredits);
}
/**
* This method cancels available credits. Following the
* cancel call the pipe will no longer be delivering messages to the
* subscriber.
*/
@Override
default void cancel()
{
throw new UnsupportedOperationException(getClass().getName());
}
/**
* Publisher callback when more credits may be available.
*
* @see OnAvailable
*/
default void onAvailable(OnAvailable ready)
{
throw new UnsupportedOperationException(getClass().getName());
}
/**
* Method offerTimeout configures how long the Pipe.next() will wait for
* queue to accept next message before throwing an IllegalStateException
* with no credits available message.
*
* @param timeout timeout value
* @param unit timeout unit modifier
*/
default void offerTimeout(long timeout, TimeUnit unit)
{
throw new UnsupportedOperationException(getClass().getName());
}
/**
* Publisher callback when more credits may be available.
*/
@FunctionalInterface
interface OnAvailable
{
/**
* Method called when more credits are available
*/
void available();
/**
* Method called when method fail is called on a publisher pipe
*/
default void fail(Throwable exn)
{
}
/**
* Method called
*/
default void cancel()
{
}
}
}