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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.messagebus;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A session which supports receiving, forwarding and acknowledging messages. An intermediate session is expected
* to either forward or acknowledge every message received.
*
* @author Simon Thoresen Hult
*/
public final class IntermediateSession implements MessageHandler, ReplyHandler, Connectable {
private final AtomicBoolean destroyed = new AtomicBoolean(false);
private final String name;
private final boolean broadcastName;
private final MessageHandler msgHandler;
private final ReplyHandler replyHandler;
private final MessageBus mbus;
/**
* This constructor is declared package private since only MessageBus is supposed to instantiate it.
*
* @param mbus The message bus that created this instance.
* @param params The parameter object for this session.
*/
IntermediateSession(MessageBus mbus, IntermediateSessionParams params) {
this.mbus = mbus;
this.name = params.getName();
this.broadcastName = params.getBroadcastName();
this.msgHandler = params.getMessageHandler();
this.replyHandler= params.getReplyHandler();
}
/**
* Sets the destroyed flag to true. The very first time this method is called, it cleans up all its dependencies.
* Even if you retain a reference to this object, all of its content is allowed to be garbage collected.
*
* @return true if content existed and was destroyed
*/
public boolean destroy() {
if (!destroyed.getAndSet(true)) {
close();
return true;
}
return false;
}
/**
* This method unregisters this session from message bus, effectively disabling any more messages from being
* delivered to the message handler. After unregistering, this method calls {@link com.yahoo.messagebus.MessageBus#sync()}
* to ensure that there are no threads currently entangled in the handler.
*
* This method will deadlock if you call it from the message or reply handler.
*/
public void close() {
mbus.unregisterSession(name, broadcastName);
mbus.sync();
}
/**
* Forwards a routable to the next hop in its route. This method will never block.
* @param routable the routable to forward.
*/
public void forward(Routable routable) {
if (routable instanceof Reply) {
Reply reply = (Reply)routable;
ReplyHandler handler = reply.popHandler();
handler.handleReply(reply);
} else {
routable.pushHandler(this);
mbus.handleMessage((Message)routable);
}
}
/** Returns the message handler of this session */
public MessageHandler getMessageHandler() {
return msgHandler;
}
/**
* Returns the reply handler of this session.
*
* @return The reply handler.
*/
public ReplyHandler getReplyHandler() {
return replyHandler;
}
/**
* Returns the connection spec string for this session. This returns a combination of the owning message bus' own
* spec string and the name of this session.
*/
public String getConnectionSpec() {
return mbus.getConnectionSpec() + "/" + name;
}
/** Returns the name of this session */
public String getName() {
return name;
}
@Override
public void handleMessage(Message msg) {
msgHandler.handleMessage(msg);
}
@Override
public void handleReply(Reply reply) {
if (destroyed.get()) {
reply.discard();
} else {
replyHandler.handleReply(reply);
}
}
@Override
public void connect() {
mbus.connect(name, broadcastName);
}
@Override
public void disconnect() { close(); }
}
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