public Task <IStatefulGrain> GetGrain()
{
string primaryKey = null;
bool renewlease = true;
if (State.numInstances >= Parameters.NUM_REPLICAS)
{
var stubReplicas = State.replicas.Where(x => DateTime.Now - x.Value > Parameters.LEASE_DURATION);
if (stubReplicas.Count() > 0)
{
primaryKey = stubReplicas.ElementAt(rnd.Next(0, stubReplicas.Count())).Key;
}
else
{
primaryKey = State.replicas.ElementAt(rnd.Next(0, Parameters.NUM_REPLICAS)).Key;
renewlease = false;
}
}
else
{
primaryKey = WITWDMetadataGrain.WITWD_REPLICA + State.numInstances++;
}
IWhereInTheWorldData grain = GrainFactory.GetGrain <IWhereInTheWorldData>(primaryKey);
if (renewlease)
{
var leaseStartTime = DateTime.Now;
grain.StartLease(leaseStartTime);
State.replicas.Add(primaryKey, leaseStartTime);
}
return(Task.FromResult <IStatefulGrain>(grain));
}
public Task <IWhereInTheWorldData> GetNearestFullReplica()
{
// Adding some offset so that we do not pick replica whose lease is soon to expire
var fullReplicas = State.replicas.Where(x => DateTime.Now - x.Value <= Parameters.LEASE_DURATION - new TimeSpan(0, 3, 0));
if (fullReplicas.Count() > 0)
{
string primaryKey = fullReplicas.ElementAt(rnd.Next(0, fullReplicas.Count())).Key;
IWhereInTheWorldData grain = GrainFactory.GetGrain <IWhereInTheWorldData>(primaryKey);
return(Task.FromResult <IWhereInTheWorldData>(grain));
}
return(null);
}
