private FileData ReadFileData(int fileRegisterIndex, Helper.Semantics semantics)
{
// gets latest version
LatestVersion latestVersion = ReadVersion(fileRegisterIndex, semantics);
// requests file data to dataServer with latest version
List <string> dataServersIds = latestVersion.DataServerIds;
// loops until we get something from a read from any dataServer
while (true)
{
foreach (string id in dataServersIds)
{
string location = fileRegister.FileMetadataAt(fileRegisterIndex).Locations[id];
string localFilename = fileRegister.FileMetadataAt(fileRegisterIndex).LocalFilenames[id];
IDataServerToClient dataServer = (IDataServerToClient)Activator.GetObject(
typeof(IDataServerToClient),
location);
try
{
FileData fileData = dataServer.Read(localFilename);
// update file registers
fileRegister.SetFileDataAt(fileRegisterIndex, fileData);
return(fileData);
}
catch (ProcessFailedException) { }
catch (ProcessFreezedException) { }
}
}
}
public void Write(int fileRegisterIndex, byte[] contents)
{
Console.WriteLine("WRITE FILE = " + fileRegisterIndex);
try
{
// forces to get always the most recent file
FileVersion latest = ReadVersion(fileRegisterIndex, Helper.Semantics.MONOTONIC).Version;
latest.Increment(Client.id);
FileData fileData = new FileData(latest, contents);
string filename = fileRegister.FilenameAt(fileRegisterIndex);
FileMetadata fileMetadata = fileRegister.FileMetadataAt(fileRegisterIndex);
// data server id / bool write
ConcurrentDictionary <string, bool> writes = new ConcurrentDictionary <string, bool>();
int requests = 0;
bool quorumReached = false;
//QUORUM
while (true)
{
// voting
WriteQuorum quorum = new WriteQuorum(fileMetadata.WriteQuorum);
foreach (var entry in writes)
{
bool vote = entry.Value;
quorum.AddVote(vote);
if (quorum.CheckQuorum())
{
quorumReached = true;
break;
}
}
// found the quorum file
if (quorumReached)
{
break;
}
// if there are still pending requests
// dont create new ones
if (requests > 0)
{
continue;
}
// if all the votes arrived at the quorum
// stops when all requests are counted (requests = 0)
if (quorum.Count == (requests + quorum.Count))
{
// get possible new fileMetadata locations
// possible optimization
// check if there are no dataa servers
fileMetadata = OpenFileMetadata(filename);
// broadcast to all dataServers that have that file
foreach (var entry in fileMetadata.Locations)
{
string id = entry.Key;
string location = entry.Value;
string localFilename = fileMetadata.LocalFilenames[id];
// increment right away so it doesn't request untill its decremented
Interlocked.Increment(ref requests);
Thread request = new Thread(() =>
{
IDataServerToClient dataServer = (IDataServerToClient)Activator.GetObject(
typeof(IDataServerToClient),
location);
bool vote = false;
try
{
dataServer.Write(localFilename, fileData);
vote = true;
}
catch (ProcessFailedException) { }
catch (ProcessFreezedException) { }
finally
{
writes[id] = vote;
Interlocked.Decrement(ref requests);
}
});
request.Start();
}
}
}
// update file registers
fileRegister.SetFileDataAt(fileRegisterIndex, fileData);
}
catch (FileDoesNotExistException e)
{
Console.WriteLine(e.Message);
return;
}
}
private LatestVersion ReadVersion(int fileRegisterIndex, Helper.Semantics semantics)
{
Console.WriteLine("READ VERSION " + fileRegisterIndex);
string filename = fileRegister.FilenameAt(fileRegisterIndex);
FileVersion original = fileRegister.FileDataAt(fileRegisterIndex).Version;
FileMetadata fileMetadata = fileRegister.FileMetadataAt(fileRegisterIndex);
// data server id / file data
ConcurrentDictionary <string, FileVersion> reads = new ConcurrentDictionary <string, FileVersion>();
int requests = 0;
LatestVersion quorumVersion = null;
//QUORUM
while (true)
{
// voting
ReadQuorum quorum = new ReadQuorum(fileMetadata.ReadQuorum, semantics);
foreach (var entry in reads)
{
FileVersion vote = entry.Value;
string dataServerId = entry.Key;
quorum.AddVote(vote, dataServerId);
if (quorum.CheckQuorum(vote, original))
{
quorumVersion = new LatestVersion(vote, quorum.DataServersIds(vote));
break;
}
}
// found the quorum file
if (quorumVersion != null)
{
break;
}
// if there are still pending requests
// dont create new ones
if (requests > 0)
{
continue;
}
// if all the votes arrived at the quorum
// stops when all requests are counted (requests = 0)
if (quorum.Count == (requests + quorum.Count))
{
// get possible new fileMetadata locations
// possible optimization
// check if there are no data servers
fileMetadata = OpenFileMetadata(filename);
// broadcast to all dataServers that have that file
foreach (var entry in fileMetadata.Locations)
{
string id = entry.Key;
string location = entry.Value;
string localFilename = fileMetadata.LocalFilenames[id];
// increment right away so it doesn't request untill its decremented
Interlocked.Increment(ref requests);
Thread request = new Thread(() =>
{
IDataServerToClient dataServer = (IDataServerToClient)Activator.GetObject(
typeof(IDataServerToClient),
location);
FileVersion fileVersion = null;
try
{
fileVersion = dataServer.Version(localFilename);
}
catch (ProcessFailedException) { }
catch (ProcessFreezedException) { }
finally
{
reads[id] = fileVersion;
Interlocked.Decrement(ref requests);
}
});
request.Start();
}
}
}
return(quorumVersion);
}
