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package org.gnunet.consensus;
import org.gnunet.mq.Envelope;
import org.gnunet.mq.MessageQueue;
import org.gnunet.mq.NotifySentHandler;
import org.gnunet.util.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Multi-peer set reconciliation.
*/
public class Consensus {
/**
* Class logger.
*/
private static final Logger logger = LoggerFactory
.getLogger(Consensus.class);
/**
* Callback for new elements arriving from the service.
* Also used to notify of consensus failure.
*/
private final NewElementCallback newElementCallback;
/**
* Client connected to the consensus service.
*/
private Client client;
/**
* Called when conclude has finished.
*/
private ConcludeCallback concludeCallback;
/**
* Message dispatch for messages from the consensus service.
*/
private class ConsensusMessageReceiver extends RunaboutMessageReceiver {
public void visit(ConcludeDoneMessage m) {
if (null == concludeCallback)
{
logger.error("unexpected conclude done message");
return;
}
concludeCallback.onConcludeDone();
}
public void visit(NewElementMessage m) {
ConsensusElement element = new ConsensusElement();
element.element_type = m.element_type;
element.data = m.element_data;
newElementCallback.onNewElement(element);
}
@Override
public void handleError() {
newElementCallback.onNewElement(null);
}
}
/**
* Create a consensus session. The set being reconciled is initially
* empty. Only reconcile with other peers after
* GNUNET_CONSENSUS_reconcile has been called.
*
* @param num_peers number of peers in the session
* @param peers array of peers participating in this consensus session
* Inclusion of the local peer is optional.
* @param sessionId session identifier
* Allows a group of peers to have more than consensus session.
* @param newElementCallback callback, called when a new element is added to the set by
* another peer
*/
public Consensus(Configuration cfg, int num_peers, PeerIdentity[] peers, HashCode sessionId,
NewElementCallback newElementCallback) {
client = new Client("consensus", cfg);
client.installReceiver(new ConsensusMessageReceiver());
this.newElementCallback = newElementCallback;
}
/**
* Insert an element into the consensus set.
*
* @param element element to insert in the consnesus
* @param idc called when the element has been sent to the service
*/
public void insertElement (ConsensusElement element, final InsertDoneCallback idc) {
InsertElementMessage m = new InsertElementMessage();
m.element_data = element.data;
m.element_type = element.element_type;
Envelope ev = new Envelope(m);
ev.notifySent(new NotifySentHandler() {
@Override
public void onSent() {
idc.onInsertDone();
}
});
client.send(ev);
}
/**
* We are done with inserting new elements into the consensus;
* try to conclude the consensus within a given time window.
* After conclude has been called, no further elements may be
* inserted by the client.
* @param concludeCallback called when the consensus has concluded
*/
public void conclude(ConcludeCallback concludeCallback) {
if (null == concludeCallback)
throw new AssertionError("conclude with empty callback");
if (null != this.concludeCallback)
throw new AssertionError("called conclude twice");
this.concludeCallback = concludeCallback;
ConcludeMessage m = new ConcludeMessage();
client.send(m);
}
/**
* Destroy a consensus handle.
* Free all state associated with
* it, no longer call any of the callbacks.
*/
public void destroy() {
client.disconnect();
client = null;
}
}
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