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package com.orbekk.paxos;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class better be thread-safe.
*/
public class PaxosServiceImpl implements PaxosService {
private Logger logger = LoggerFactory.getLogger(getClass());
private int roundId = 0;
private int highestPromise = 0;
private String tag = "";
public PaxosServiceImpl(String tag) {
this.tag = tag;
}
@Override
public synchronized boolean propose(String clientUrl, int roundId,
int proposalNumber) {
if (roundId > this.roundId) {
newRound(roundId);
}
if (roundId < this.roundId) {
logger.info(tag + "propose({}, {}, {}) = rejected " +
"(current round: {})",
new Object[]{clientUrl, roundId, proposalNumber,
this.roundId});
return false;
}
if (proposalNumber > highestPromise) {
highestPromise = proposalNumber;
logger.info(tag + "propose({}, {}, {}) = accepted",
new Object[]{clientUrl, roundId, proposalNumber});
return true;
} else {
logger.info(tag + "propose({}, {}, {}) = rejected " +
"(promised: {})",
new Object[]{clientUrl, roundId, proposalNumber,
highestPromise});
return false;
}
}
@Override
public synchronized boolean acceptRequest(String clientUrl, int roundId,
int proposalNumber) {
if (roundId == this.roundId && proposalNumber == highestPromise) {
logger.info(tag + "acceptRequest({}, {}, {}) = accepted",
new Object[]{clientUrl, roundId, proposalNumber});
finishRound();
return true;
} else {
logger.info(tag + "acceptRequest({}, {}, {}) = rejected " +
"(roundId={}, promise={})",
new Object[]{clientUrl, roundId, proposalNumber,
this.roundId, highestPromise});
return false;
}
}
private synchronized void finishRound() {
newRound(roundId + 1);
}
private synchronized void newRound(int roundId) {
logger.info(tag + "new round: {}", roundId);
this.roundId = roundId;
highestPromise = 0;
}
}
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