/*
* Implementation of 2Phase Commit first make request to all other replicas.
* If "ACCEPT" is received from all the replicas then proceed to second phase, which is to commit changes.
* Used by the PUT and DELETE methods as they are the only ones that make write operations.
*/
public boolean TwoPCommit(String command, String key, String value) {
int accept = 0;
String result = "";
String host = "";
int portNumber = 0;
// ASK proxies at other servers in cluster
for (int a = 0; a < numReplicas; a++) {
result = "";
try {
host = InetAddress.getByName(hostPorts[a][0]).getHostAddress();
portNumber = Integer.parseInt(hostPorts[a][1]);
RMIServerInterface remoteImpl =
(RMIServerInterface)
Naming.lookup("rmi://" + host.trim() + ":" + portNumber + "/Calls");
long startTime = System.currentTimeMillis(); // Timeout after 10s
while (result.isEmpty()) {
if ((System.currentTimeMillis() - startTime) > 10000) {
log.error("Unable to ASK " + host + ":" + portNumber + "Timed-out!");
break;
}
result = remoteImpl.ASK(command, key, value);
}
} catch (Exception e) {
// TODO Auto-generated catch block
log.error("Connection to " + host + ":" + portNumber + " met error with " + e.getMessage());
}
log.info(result + " for " + host + ":" + portNumber);
if (result.trim().toUpperCase().equals(ACCEPT)) ++accept;
}
/*
* If all the replicas have accepted the requested command via the ASK method, then make commit.
*/
if (accept == numReplicas) {
for (int a = 0; a < numReplicas; a++) {
result = "";
try {
host = InetAddress.getByName(hostPorts[a][0]).getHostAddress();
portNumber = Integer.parseInt(hostPorts[a][1]);
RMIServerInterface remoteImpl =
(RMIServerInterface)
Naming.lookup("rmi://" + host.trim() + ":" + portNumber + "/Calls");
long startTime = System.currentTimeMillis(); // Timeout after 10s
while (!result.equals(ACK)) {
if ((System.currentTimeMillis() - startTime) > 10000) {
log.error("Unable to commit update to " + host + ":" + portNumber + "Timed-out!");
break;
}
if (command.toUpperCase().equals("PUT"))
result = (remoteImpl.PUT(true, host + ":" + port, key, value));
else if (command.toUpperCase().equals("DELETE"))
result = (remoteImpl.DELETE(true, host + ":" + port, key));
}
} catch (Exception e) {
log.error(
"Connection to " + host + ":" + portNumber + " met error with " + e.getMessage());
}
}
return true;
}
return false;
}
public static void main(String[] args) throws IOException {
/** max number of elements to import */
final long max = (int) 1e6;
/** Open database in temporary directory */
File dbFile = File.createTempFile("mapdb", "temp");
DB db =
DBMaker.newFileDB(dbFile)
/** disabling Write Ahead Log makes import much faster */
.transactionDisable()
.make();
long time = System.currentTimeMillis();
/**
* Source of data which randomly generates strings. In real world this would return data from
* file.
*/
Iterator<String> source =
new Iterator<String>() {
long counter = 0;
@Override
public boolean hasNext() {
return counter < max;
}
@Override
public String next() {
counter++;
return randomString(10);
}
@Override
public void remove() {}
};
/**
* BTreeMap Data Pump requires data source to be presorted in reverse order (highest to lowest).
* There is method in Data Pump we can use to sort data. It uses temporarly files and can handle
* fairly large data sets.
*/
source =
Pump.sort(
source,
true,
100000,
Collections.reverseOrder(BTreeMap.COMPARABLE_COMPARATOR), // reverse order comparator
db.getDefaultSerializer());
/**
* Disk space used by serialized keys should be minimised. Keys are sorted, so only difference
* between consequential keys is stored. This method is called delta-packing and typically saves
* 60% of disk space.
*/
BTreeKeySerializer<String> keySerializer = BTreeKeySerializer.STRING;
/** Translates Map Key into Map Value. */
Fun.Function1<Integer, String> valueExtractor =
new Fun.Function1<Integer, String>() {
@Override
public Integer run(String s) {
return s.hashCode();
}
};
/** Create BTreeMap and fill it with data */
Map<String, Integer> map =
db.createTreeMap("map")
.pumpSource(source, valueExtractor)
// .pumpPresort(100000) // for presorting data we could also use this method
.keySerializer(keySerializer)
.make();
System.out.println(
"Finished; total time: "
+ (System.currentTimeMillis() - time) / 1000
+ "s; there are "
+ map.size()
+ " items in map");
db.close();
}