public void Read(int fileRegister, Semantics semantics, int contentRegister)
{
print("Read Command Started for fileRegister=" + fileRegister + ",Semantics=" + semantics + ",ContentRegister= " + contentRegister);
Metadata md = fileRegisters[fileRegister];
Server[] sDTO = md.dataServers;
DataRequestService[] drs = new DataRequestService[md.nbDataServers];
while (sDTO.Length < md.readQuorum)
{
try
{
Console.WriteLine("To send the Read request I have DatServers=" + sDTO.Length + " less than the ReadQuorum " + md.readQuorum + ". So I will try to open the file again.");
this.Open(md.fileName);
md = fileRegisters[fileRegister];
sDTO = md.dataServers;
Console.WriteLine("After Open Request the number of dataServers are " + sDTO.Length);
}
catch (Exception e)
{
}
}
int i = 0;
for (i = 0; i < sDTO.GetLength(0); i++)
{
try
{
if (dataServices.ContainsKey(sDTO[i].address))
{
//do nothing;
}
else
{ //Get the proxy and store it in the Hashtable for future.
dataServices.Add(sDTO[i].address, (DataRequestService)Activator.GetObject(
typeof(DataRequestService),
sDTO[i].address));
}
//populate the Array.
drs[i] = (DataRequestService)dataServices[sDTO[i].address];
}
catch (Exception e)
{
}
}
if (semantics.Equals(Semantics.DEFAULT))
{
int[] versions = new int[md.nbDataServers];
int k = 0; int cnt = 0; int maxVersion; int maxId = 0;
ArrayList failedDataServers = new ArrayList();
//Initialize versions
for (k = 0; k < md.nbDataServers; k++)
{
versions[k] = -3;
}
//Try for readquorum number of DataServers.
for (k = 0; k < md.readQuorum; k++)
{
try {
versions[k] = (drs[i].GetVersion(sDTO[k].localFileName));
cnt++;
}
catch (Exception e) {
failedDataServers.Add(k);
//DataServer is Failed.
}
}
if (cnt < md.readQuorum)
{
for (k = md.readQuorum; k < md.nbDataServers; k++)
{
try {
versions[k] = (drs[i].GetVersion(sDTO[k].localFileName));
cnt++;
if (cnt >= md.readQuorum)
{
break;
}
}
catch (Exception e) {
failedDataServers.Add(k);
//DataServer is Failed.
}
}
k = 0; int index;
while (cnt < md.readQuorum)
{
index = (int)failedDataServers[k];
try {
versions[index] = (drs[index].GetVersion(sDTO[index].localFileName));
cnt++;
failedDataServers.RemoveAt(k);
}
catch (Exception e) {
//DataServer is still failed.
}
if (failedDataServers.Count != 0)
{
k = (k + 1) % failedDataServers.Count;
}
}
}
//Get the maximum version
maxVersion = 0;
for (k = 0; k < md.nbDataServers; k++)
{
if (versions[k] >= maxVersion)
{
maxVersion = versions[k];
maxId = k;
}
}
//Read and store the latest Version
String fileName = fileRegisters[fileRegister].fileName;
if (fileDetails.ContainsKey(fileName))
{
if (((Indices)fileDetails[fileName]).getLatestVersionSeen() < maxVersion)
{
((Indices)fileDetails[fileName]).setLatestVersionSeen(maxVersion);
}
}
Data contents = new Data(drs[maxId].Read(sDTO[maxId].localFileName, Semantics.DEFAULT));
if (contentRegister == -1)
{
dataRegisterForCopy = contents;
}
else
{
addContentRegister(contents, contentRegister);
}
}
else//semantics is Monotonic.
{
String fileName = fileRegisters[fileRegister].fileName;
int currentVersion = -1;
if (fileDetails.ContainsKey(fileName))
{
currentVersion = ((Indices)fileDetails[fileName]).getLatestVersionSeen();
}
else
{
Console.WriteLine("Version last seen,mcorresponding to fileRegister " + fileRegister + " Was not found in fileDetails HashTable. So returning witout Reading");
return;
}
int maxVersion = currentVersion; int maxId = 0; int temp;
int k = 0; int cnt = 0; //int responseCount = 0;
ArrayList retryServers = new ArrayList();
for (k = 0; k < md.nbDataServers; k++)
{
try {
temp = drs[k].GetVersion(sDTO[k].localFileName);
if (currentVersion < temp)
{
if (maxVersion < temp)
{
maxVersion = temp;
maxId = k;
cnt++;
}
else
{
cnt++;
}
}
else if (currentVersion == temp && maxVersion == currentVersion)
{
maxId = k;
cnt++;
}
else if (currentVersion == temp && currentVersion < maxVersion)
{
cnt++;
}
else
{
retryServers.Add(k);
}
}
catch (Exception e) {
retryServers.Add(k);
}
}
if (cnt < md.readQuorum)
{
int index = 0;
while (cnt < md.readQuorum)
{
index = (int)retryServers[k];
try {
temp = drs[index].GetVersion(sDTO[index].localFileName);
if (currentVersion < temp)
{
if (maxVersion < temp)
{
maxVersion = temp;
maxId = index;
cnt++;
}
else
{
cnt++;
}
retryServers.RemoveAt(k);
}
else if (currentVersion == temp && maxVersion == currentVersion)
{
maxId = index;
cnt++;
retryServers.RemoveAt(k);
}
else if (currentVersion == temp && currentVersion < maxVersion)
{
cnt++;
retryServers.RemoveAt(k);
}
}
catch (Exception e) {
//DataServer is still failed.
}
k = (k + 1) % retryServers.Count;
}
}
//Read and Store the max version
if (fileDetails.ContainsKey(fileName))
{
((Indices)fileDetails[fileName]).setLatestVersionSeen(maxVersion);
}
Data contents = new Data(drs[maxId].Read(sDTO[maxId].localFileName, Semantics.MONOTONIC));
if (contentRegister == -1)
{
dataRegisterForCopy = contents;
}
else
{
addContentRegister(contents, contentRegister);
}
}
print("Read Command execution complete for fileRegister=" + fileRegister + ",Semantics=" + semantics + ",ContentRegister= " + contentRegister);
}
