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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.CountDownLatch;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.atomic.AtomicInteger;
import org.junit.runner.Request;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.protobuf.RpcCallback;
import com.orbekk.protobuf.Rpc;
import com.orbekk.same.ConnectionManager;
import com.orbekk.same.Services;
import com.orbekk.same.Services.ClientState;
import com.orbekk.same.Services.PaxosRequest;
import com.orbekk.same.Services.PaxosResponse;
public class MasterProposer extends Thread {
private final Logger logger = LoggerFactory.getLogger(getClass());
private final ClientState client;
private final List<String> paxosLocations;
private final ConnectionManager connections;
public MasterProposer(ClientState client, List<String> paxosLocations,
ConnectionManager connections) {
this.client = client;
this.paxosLocations = paxosLocations;
this.connections = connections;
}
private class ResponseHandler implements RpcCallback<PaxosResponse> {
final int proposalNumber;
final int numRequests;
AtomicInteger bestPromise = new AtomicInteger();
AtomicInteger numPromises = new AtomicInteger(0);
AtomicInteger numResponses = new AtomicInteger(0);
AtomicInteger result = new AtomicInteger();
CountDownLatch done = new CountDownLatch(1);
public ResponseHandler(int proposalNumber, int numRequests) {
this.proposalNumber = proposalNumber;
this.numRequests = numRequests;
bestPromise.set(-proposalNumber);
}
@Override public void run(PaxosResponse response) {
numResponses.incrementAndGet();
if (response != null) {
int result = response.getResult();
if (result == proposalNumber) {
numPromises.incrementAndGet();
}
while (true) {
int oldVal = bestPromise.get();
int update = Math.min(oldVal, result);
if (bestPromise.compareAndSet(oldVal, update)) {
break;
}
}
}
checkDone();
}
private void checkDone() {
if (done.getCount() > 0) {
if (numPromises.get() >= numRequests / 2) {
result.set(proposalNumber);
done.countDown();
} else if (numResponses.get() >= numRequests) {
result.set(bestPromise.get());
done.countDown();
}
}
}
public int getResult() throws InterruptedException {
done.await();
return result.get();
}
}
private int internalPropose(int proposalNumber)
throws InterruptedException {
ResponseHandler handler = new ResponseHandler(proposalNumber,
paxosLocations.size());
for (String location : paxosLocations) {
Rpc rpc = new Rpc();
Services.Paxos paxos = connections.getPaxos0(location);
if (paxos == null) {
handler.run(null);
continue;
}
PaxosRequest request = PaxosRequest.newBuilder()
.setClient(client)
.setProposalNumber(proposalNumber)
.build();
paxos.propose(rpc, request, handler);
}
return handler.getResult();
}
private int internalAcceptRequest(int proposalNumber)
throws InterruptedException {
ResponseHandler handler = new ResponseHandler(proposalNumber,
paxosLocations.size());
for (String location : paxosLocations) {
Rpc rpc = new Rpc();
Services.Paxos paxos = connections.getPaxos0(location);
PaxosRequest request = PaxosRequest.newBuilder()
.setClient(client)
.setProposalNumber(proposalNumber)
.build();
paxos.acceptRequest(rpc, request, handler);
}
return handler.getResult();
}
boolean propose(int proposalNumber) throws InterruptedException {
int result = internalPropose(proposalNumber);
if (result == proposalNumber) {
result = internalAcceptRequest(proposalNumber);
}
if (result == proposalNumber) {
return true;
} else {
return false;
}
}
boolean proposeRetry(int proposalNumber) throws InterruptedException {
return proposeRetry(proposalNumber, null) != null;
}
Integer proposeRetry(int proposalNumber, Runnable retryAction)
throws InterruptedException {
assert proposalNumber > 0;
int nextProposal = proposalNumber;
int result = nextProposal - 1;
while (!Thread.currentThread().isInterrupted() && 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()) {
throw new InterruptedException();
}
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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