org.cometd.client.ext.AckExtension Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2021 the original author or authors.
*
* Licensed 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.cometd.client.ext;
import java.util.Map;
import org.cometd.bayeux.Channel;
import org.cometd.bayeux.Message.Mutable;
import org.cometd.bayeux.client.ClientSession;
import org.cometd.bayeux.client.ClientSession.Extension;
/**
* This client-side extension enables the client to acknowledge to the server
* the messages that the client has received.
* For the acknowledgement to work, the server must be configured with the
* correspondent server-side ack extension. If both client and server support
* the ack extension, then the ack functionality will take place automatically.
* By enabling this extension, all messages arriving from the server will arrive
* via the long poll, so the comet communication will be slightly chattier.
* The fact that all messages will return via long poll means also that the
* messages will arrive with total order, which is not guaranteed if messages
* can arrive via both long poll and normal response.
* Messages are not acknowledged one by one, but instead a group of messages is
* acknowledged when long poll returns.
*/
public class AckExtension implements Extension {
public static final String ACK_FIELD = "ack";
private boolean _serverSupportsAcks;
private long _batch;
@Override
public boolean rcvMeta(ClientSession session, Mutable message) {
if (Channel.META_HANDSHAKE.equals(message.getChannel())) {
Map ext = message.getExt(false);
if (ext != null) {
Object field = ext.get(ACK_FIELD);
if (field instanceof Map) {
// New format.
@SuppressWarnings("unchecked")
Map ack = (Map)field;
_serverSupportsAcks = Boolean.TRUE.equals(ack.get("enabled"));
Object batch = ack.get("batch");
if (batch instanceof Number) {
_batch = ((Number)batch).longValue();
}
} else {
// Old format.
_serverSupportsAcks = Boolean.TRUE.equals(field);
}
}
} else if (Channel.META_CONNECT.equals(message.getChannel()) && message.isSuccessful() && _serverSupportsAcks) {
Map ext = message.getExt(false);
if (ext != null) {
Object ack = ext.get(ACK_FIELD);
if (ack instanceof Number) {
_batch = ((Number)ack).longValue();
}
}
}
return true;
}
@Override
public boolean sendMeta(ClientSession session, Mutable message) {
if (Channel.META_HANDSHAKE.equals(message.getChannel())) {
_serverSupportsAcks = false;
_batch = 0;
message.getExt(true).put(ACK_FIELD, Boolean.TRUE);
} else if (Channel.META_CONNECT.equals(message.getChannel())) {
if (_serverSupportsAcks) {
message.getExt(true).put(ACK_FIELD, _batch);
}
}
return true;
}
}