org.apache.qpid.proton.reactor.FlowController Maven / Gradle / Ivy
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.qpid.proton.reactor;
import org.apache.qpid.proton.engine.BaseHandler;
import org.apache.qpid.proton.engine.Event;
import org.apache.qpid.proton.engine.Link;
import org.apache.qpid.proton.engine.Receiver;
/**
* A handler that applies flow control to a connection. This handler tops-up
* link credit each time credit is expended by the receipt of messages.
*/
public class FlowController extends BaseHandler {
private int drained;
private int window;
public FlowController(int window) {
// XXX: a window of 1 doesn't work because we won't necessarily get
// notified when the one allowed delivery is settled
if (window <= 1) throw new IllegalArgumentException();
this.window = window;
this.drained = 0;
}
public FlowController() {
this(1024);
}
private void topup(Receiver link, int window) {
int delta = window - link.getCredit();
link.flow(delta);
}
@Override
public void onUnhandled(Event event) {
int window = this.window;
Link link = event.getLink();
switch(event.getType()) {
case LINK_LOCAL_OPEN:
case LINK_REMOTE_OPEN:
case LINK_FLOW:
case DELIVERY:
if (link instanceof Receiver) {
this.drained += link.drained();
if (this.drained == 0) {
topup((Receiver)link, window);
}
}
break;
default:
break;
}
}
}