/**
* LOAD BALANCING
*/
private void LoadBalancing()
{
if (fail)
{
return;
}
if (!ImMaster)
{
return;
}
HashSet <string> alreadyMigrated = new HashSet <string>();
foreach (DataServerFile file in dataServers.FileWeights)
{
string localFilename = file.LocalFilename;
string filename = fileTable.FilenameByLocalFilename(localFilename);
Weight fileWeight = file.Weight;
string oldDataServerId = file.DataServerId;
Weight oldDataServerWeight = dataServers.Weight(oldDataServerId);
Weight avgWeight = dataServers.AvgWeight;
// if the file has no reads or writes
if (Weight.Empty(fileWeight))
{
continue;
}
// if data server is already balanced
if (Weight.BelowThreshold(oldDataServerWeight, avgWeight, Helper.LOAD_BALANCING_THRESHOLD))
{
continue;
}
foreach (var entry in dataServers.Weights)
{
string newDataServerId = entry.Key;
Weight newDataServerWeight = entry.Value;
// BLACK LIST SKIP CASES
// skips if its the old dataServer
if (newDataServerId == oldDataServerId)
{
continue;
}
// migrates just one file per data server
if (alreadyMigrated.Contains(newDataServerId))
{
continue;
}
// if file already is in dataserver
if (fileTable.FileInDataServer(filename, newDataServerId))
{
continue;
}
// if data server is known to be down
if (dataServers.Failed(newDataServerId))
{
continue;
}
// if the data server is already overweight
if (Weight.AboveThreshold(newDataServerWeight, avgWeight, Helper.LOAD_BALANCING_THRESHOLD))
{
continue;
}
// if placing the new file would put that server above threshold
if (Weight.AboveThreshold(fileWeight + newDataServerWeight, avgWeight, Helper.LOAD_BALANCING_THRESHOLD))
{
continue;
}
// if it isnt free
if (!fileTable.Free(filename))
{
continue;
}
// LOCK
fileTable.Lock(filename);
// reads from old, writes to new
string newLocalFilename = LocalFilename(filename, newDataServerId);
string oldLocalFilename = fileTable.LocalFilenameByFilename(filename, oldDataServerId);
// if swap was false migration failed
bool swaped = SwapDataServers(oldDataServerId, newDataServerId, oldLocalFilename, newLocalFilename, fileWeight);
if (swaped)
{
Console.WriteLine("MIGRATE " + filename + " TO " + newDataServerId);
// log operation
int sequence = clock++;
log.LogOperation(sequence, "MigrateFileOnMetadata", filename, oldDataServerId, newDataServerId, oldLocalFilename, newLocalFilename, sequence);
// swap files on data server register
dataServers.AddFile(newDataServerId, newLocalFilename);
dataServers.RemoveFile(oldDataServerId, oldLocalFilename);
// swaps data servers on file table
fileTable.RemoveDataServer(filename, oldDataServerId);
fileTable.AddDataServer(filename, newDataServerId, dataServers.Location(newDataServerId), newLocalFilename);
// migrate to metadatas
MigrateFileOnMetadatas(filename, oldDataServerId, newDataServerId, oldLocalFilename, newLocalFilename, sequence);
// adds file weight to data server weight and removes from previous
dataServers.AddWeight(newDataServerId, fileWeight);
dataServers.RemoveWeight(oldDataServerId, fileWeight);
// adds to data servers already migrated
alreadyMigrated.Add(newDataServerId);
}
// UNLOCK
fileTable.Unlock(filename);
// if migration occured breaks this data server loop file
if (swaped)
{
break;
}
}
}
}