/*
* (non-Javadoc)
* @see project3.RMIServerInterface#ASK(java.lang.String, java.lang.String, java.lang.String)
* ASK method checks with the replica that the command being requested with the key and value is legitimate and acceptable to the server.
* If the value is not being modified for the key passed in, then reject.
* Similarly, if the key doesn't exist in the replica, then ASK would reject for this replica.
* Enforces consistency of data in the absence of failures.
*/
@Override
public String ASK(String command, String key, String value) {
if (hash.containsKey(key)) {
String existingVal = hash.get(key);
if (command.toUpperCase().equals("PUT"))
if (!existingVal.equals(value)) return "ACCEPT";
else return "REJECT";
else return "ACCEPT";
} else {
if (command.toUpperCase().equals("PUT")) return "ACCEPT";
else return "REJECT";
}
}
public String GET(String clientId, String key) {
log.info(
"Server at "
+ hostname
+ ":"
+ port
+ " "
+ "received [GET "
+ key
+ "] from client "
+ clientId);
String response = "";
if (hash.containsKey(key)) response = hash.get(key);
else {
response = "No key " + key + " matches db ";
log.error(response);
}
return response;
}
public String DELETE(boolean go, String clientId, String key) {
// synchronize delete function on hash
if (go) {
log.info(
"Server at "
+ hostname
+ ":"
+ port
+ " "
+ "received [DELETE "
+ key
+ "] from client "
+ clientId);
String response = "";
if (hash.containsKey(key)) {
hash.remove(key);
response = ACK;
} else {
response = "No such key - " + key + " exists";
log.error(response);
}
return response;
} else return TwoPCommit("DELETE", key, "") ? ACK : NACK;
}
/*
* (non-Javadoc)
* @see project3.RMIServerInterface#PUT(boolean, java.lang.String, java.lang.String, java.lang.String)
* Two phase commit for PUT operation. Only if go is true. we would commit to disk.
*/
public String PUT(boolean go, String clientId, String key, String value) {
if (go) {
log.info(
"Server at "
+ hostname
+ ":"
+ port
+ " "
+ "received [PUT "
+ key
+ "|"
+ value.trim()
+ "] from client "
+ clientId);
String response = "";
// this would overwrite the values of the key
hash.put(key, value);
response = ACK;
return response;
} else return TwoPCommit("PUT", key, value) ? ACK : NACK;
}