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package com.orbekk.paxos;
import static com.orbekk.same.StackTraceUtil.throwableToString;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.orbekk.same.ConnectionManager;
public class MasterProposer extends Thread {
private Logger logger = LoggerFactory.getLogger(getClass());
private String myUrl;
private List<String> paxosUrls = new ArrayList<String>();
private ConnectionManager connections;
public MasterProposer(String clientUrl, List<String> paxosUrls,
ConnectionManager connections) {
this.myUrl = clientUrl;
this.paxosUrls = paxosUrls;
this.connections = connections;
}
private int internalPropose(int proposalNumber) {
int bestPromise = -proposalNumber;
int promises = 0;
for (String url : paxosUrls) {
PaxosService paxos = connections.getPaxos(url);
int result = 0;
try {
result = paxos.propose(myUrl, proposalNumber);
} catch (Exception e) {
logger.warn("Exception from {}: {}", url,
throwableToString(e));
}
if (result == proposalNumber) {
promises += 1;
}
bestPromise = Math.min(bestPromise, result);
}
if (promises > paxosUrls.size() / 2) {
return proposalNumber;
} else {
return bestPromise;
}
}
private int internalAcceptRequest(int proposalNumber) {
int bestAccepted = -proposalNumber;
int accepts = 0;
for (String url : paxosUrls) {
PaxosService paxos = connections.getPaxos(url);
int result = 0;
try {
result = paxos.acceptRequest(myUrl, proposalNumber);
} catch (Exception e) {
logger.warn("Exception from {}: {}", url,
throwableToString(e));
}
if (result == proposalNumber) {
accepts += 1;
}
bestAccepted = Math.min(bestAccepted, result);
}
if (accepts > paxosUrls.size() / 2) {
return proposalNumber;
} else {
return bestAccepted;
}
}
boolean propose(int proposalNumber) {
int result = internalPropose(proposalNumber);
if (result == proposalNumber) {
result = internalAcceptRequest(proposalNumber);
}
if (result == proposalNumber) {
return true;
} else {
return false;
}
}
boolean proposeRetry(int proposalNumber) {
return proposeRetry(proposalNumber, null) != null;
}
Integer proposeRetry(int proposalNumber, Runnable retryAction) {
assert proposalNumber > 0;
int nextProposal = proposalNumber;
int result = nextProposal - 1;
while (!Thread.interrupted() && result != nextProposal) {
result = internalPropose(nextProposal);
if (result == nextProposal) {
result = internalAcceptRequest(nextProposal);
}
logger.info("Proposed value {}, result {}", nextProposal, result);
if (result < 0) {
nextProposal = -result + 1;
if (retryAction != null) {
retryAction.run();
}
}
}
if (Thread.interrupted()) {
return null;
}
return result;
}
public Future<Integer> startProposalTask(final int proposalNumber,
final Runnable retryAction) {
Callable<Integer> proposalCallable = new Callable<Integer>() {
@Override public Integer call() throws Exception {
return proposeRetry(proposalNumber, retryAction);
}
};
FutureTask<Integer> task = new FutureTask<Integer>(proposalCallable);
new Thread(task).start();
return task;
}
}
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