// Master tells the worker to fail itself and stabilizes the system
internal static bool fail(string url)
{
if (isFailedServer(url))
{
return(false);
}
int id = getAvailableID(url);
if (isFreezedServer(url))
{
freezedServers.Remove(id);
}
failedServers.Add(id, url);
string failed_sucessorURL = getWorkerSucessor(id);
string failed_predecessorURL = getWorkerPredecessor(id);
IMasterWorker failed_sucessor = (IMasterWorker)Activator.GetObject(
typeof(IMasterWorker), failed_sucessorURL + "MasterWorker");
IMasterWorker failed_predecessor = (IMasterWorker)Activator.GetObject(
typeof(IMasterWorker), failed_predecessorURL + "MasterWorker");
// Na posicao original dos available trocar o url pelo sucessor
availableServers[id] = failed_sucessorURL;
//Set sucessor of failed_predecessor to failed_sucessor -> Problema de concorrencia entre estas 2 operções?
failed_predecessor.setSucessor(failed_sucessorURL);
//Tell the sucessor to substitute the failed server
failed_sucessor.substituteFailedServer();
//Tell the sucessor to fetch the original data from the failed_predecessor and put it in his the list of updates
failed_sucessor.fetch_data(failed_predecessorURL);
IMasterWorker datastore = (IMasterWorker)Activator.GetObject(
typeof(IMasterWorker), url + "MasterWorker");
// Last thing to do is change the state, so that the library can continue working
datastore.fail();
return(true);
}
// Sets the detected url to failed
internal static string setFailedServer(string url)
{
// simple sanity check
if (!failedServers.ContainsValue(url))
{
// if the server was available do the following
if (availableServers.ContainsValue(url))
{
lock (availableServers)
{
int id = getAvailableID(url);
int sucessorID = id + 1;
if (sucessorID >= availableServers.Count)
{
sucessorID = 0;
}
int predecessorID = id - 1;
if (predecessorID < 0)
{
predecessorID = availableServers.Count;
}
string predecessorURL = availableServers[predecessorID];
string sucessorURL = availableServers[sucessorID];
string failedURL = availableServers[id];
IMasterWorker sucessor =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
sucessorURL + "MasterWorker");
IMasterWorker predecessor =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
predecessorURL + "MasterWorker");
IMasterWorker failed =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
failedURL + "MasterWorker");
availableServers[id] = sucessorURL; // same as availableServers[successorID]
sucessor.setPredecessor(predecessorURL);
predecessor.setSucessor(sucessorURL);
sucessor.substituteFailedServer();
failed.fail();
failedServers.Add(id, url);
return(sucessorURL);
}
}
else if (freezedServers.ContainsValue(url))
{
lock (freezedServers)
{
int id = getFreezeID(url);
int sucessorID = id + 1;
if (sucessorID >= freezedServers.Count)
{
sucessorID = 0;
}
int predecessorID = id - 1;
if (predecessorID < 0)
{
predecessorID = freezedServers.Count;
}
string predecessorURL = freezedServers[predecessorID];
string sucessorURL = freezedServers[sucessorID];
string failedURL = freezedServers[id];
IMasterWorker sucessor =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
sucessorURL + "MasterWorker");
IMasterWorker predecessor =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
predecessorURL + "MasterWorker");
IMasterWorker failed =
(IMasterWorker)Activator.GetObject(typeof(IMasterWorker),
failedURL + "MasterWorker");
// the server was both in available and freezed servers
availableServers[id] = sucessorURL;
sucessor.setPredecessor(predecessorURL);
predecessor.setSucessor(sucessorURL);
sucessor.substituteFailedServer();
failed.fail();
freezedServers.Remove(id);
failedServers.Add(id, url);
return(sucessorURL);
}
}
}
return(null);
}