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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 highestPromise = 0;
private int highestAcceptedValue = 0;
private String tag = "";
public PaxosServiceImpl(String tag) {
this.tag = tag;
}
@Override
public 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;
}
}
@Override
public 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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