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/**
* Copyright 2012 Kjetil Ørbekk <kjetil.orbekk@gmail.com>
*
* 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 com.orbekk.paxos;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.protobuf.RpcCallback;
import com.google.protobuf.RpcController;
import com.orbekk.same.Services.Paxos;
import com.orbekk.same.Services.PaxosRequest;
import com.orbekk.same.Services.PaxosResponse;
/**
* This class better be thread-safe.
*/
public class PaxosServiceImpl {
private Logger logger = LoggerFactory.getLogger(getClass());
private int highestPromise = 0;
private int highestAcceptedValue = 0;
private String tag = "";
private Paxos service = new ProtobufPaxosServiceImpl();
private class ProtobufPaxosServiceImpl extends Paxos {
@Override
public void propose(RpcController controller, PaxosRequest request,
RpcCallback<PaxosResponse> done) {
logger.info("propose({}). Highest promise: {}, Highest accepted: {}",
new Object[]{request, highestPromise, highestAcceptedValue});
String clientUrl = request.getClient().getLocation();
int proposalNumber = request.getProposalNumber();
int response =
PaxosServiceImpl.this.propose(clientUrl, proposalNumber);
PaxosResponse result = PaxosResponse.newBuilder()
.setResult(response)
.build();
done.run(result);
}
@Override
public void acceptRequest(RpcController controller,
PaxosRequest request, RpcCallback<PaxosResponse> done) {
logger.info("acceptRequest({}). Highest promise: {}, Highest accepted: {}",
new Object[]{request, highestPromise, highestAcceptedValue});
String clientUrl = request.getClient().getLocation();
int proposalNumber = request.getProposalNumber();
int response =
PaxosServiceImpl.this.acceptRequest(clientUrl, proposalNumber);
PaxosResponse result = PaxosResponse.newBuilder()
.setResult(response)
.build();
done.run(result);
}
}
public PaxosServiceImpl(String tag) {
this.tag = tag;
}
public Paxos getService() {
return service;
}
private synchronized int propose(String clientUrl,
int proposalNumber) {
if (proposalNumber > highestPromise) {
logger.info(tag + "propose({}, {}) = accepted",
new Object[]{clientUrl, proposalNumber});
highestPromise = proposalNumber;
return highestPromise;
} else {
logger.info(tag + "propose({}, {}) = rejected " +
"(promised: {})",
new Object[]{clientUrl, proposalNumber,
highestPromise});
return -highestPromise;
}
}
private synchronized int acceptRequest(String clientUrl,
int proposalNumber) {
if (proposalNumber == highestPromise) {
logger.info(tag + "acceptRequest({}, {}) = accepted",
new Object[]{clientUrl, proposalNumber});
highestAcceptedValue = proposalNumber;
return highestAcceptedValue;
} else {
logger.info(tag + "acceptRequest({}, {}) = rejected " +
"(promise={})",
new Object[]{clientUrl, proposalNumber,
highestPromise});
return -highestPromise;
}
}
}
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