public async Task <string> ReserveAny(string scope, string ownerToken, TimeSpan?lease = null, string confirmationToken = null)
{
if (scope == null)
{
throw new ArgumentNullException("scope");
}
if (ownerToken == null)
{
throw new ArgumentNullException("ownerToken");
}
var now = Clock.Now();
using (var db = CreateReservationServiceDbContext())
{
var reservedValues = db.Set <ReservedValue>();
var expiration = now + (lease ?? TimeSpan.FromMinutes(1));
ReservedValue valueToReserve = null;
do
{
valueToReserve = reservedValues.SingleOrDefault(r => r.OwnerToken == ownerToken &&
r.ConfirmationToken == confirmationToken &&
r.Expiration != null);
if (valueToReserve == null)
{
valueToReserve = GetValueToReserve(reservedValues, scope, now);
}
if (valueToReserve == null)
{
return(null);
}
valueToReserve.Expiration = expiration;
valueToReserve.OwnerToken = ownerToken;
if (confirmationToken != null)
{
valueToReserve.ConfirmationToken = confirmationToken;
}
try
{
db.SaveChanges();
return(valueToReserve.Value);
}
catch (Exception exception)
{
if (!exception.IsConcurrencyException() || exception.IsUniquenessConstraint())
{
throw;
}
db.Entry(valueToReserve).State = EntityState.Unchanged;
}
} while (valueToReserve != null); //retry on concurrency exception
}
return(null);
}
protected bool Equals(ReservedValue other)
{
return(string.Equals(OwnerToken, other.OwnerToken) &&
string.Equals(Value, other.Value) &&
string.Equals(ConfirmationToken, other.ConfirmationToken) &&
string.Equals(Scope, other.Scope) &&
IsEqualTo(Expiration, other.Expiration));
}
private static bool VerifyOwnerToken(string ownerToken, ReservedValue reservedValue)
{
return(reservedValue.OwnerToken == ownerToken);
}
public Task <bool> Reserve(string value, string scope, string ownerToken, TimeSpan?lease = null)
{
if (value == null)
{
throw new ArgumentNullException("value");
}
if (scope == null)
{
throw new ArgumentNullException("scope");
}
if (ownerToken == null)
{
throw new ArgumentNullException("ownerToken");
}
var now = Clock.Now();
return(Task.Run(() =>
{
using (var db = CreateReservationServiceDbContext())
{
var reservedValues = db.Set <ReservedValue>();
var expiration = now + (lease ?? TimeSpan.FromMinutes(1));
// see if there is a pre-existing lease by the same actor
var reservedValue = reservedValues.SingleOrDefault(r => r.Scope == scope &&
r.Value == value);
if (reservedValue == null)
{
// if not, create a new ticket
reservedValue = new ReservedValue
{
OwnerToken = ownerToken,
Scope = scope,
Value = value,
Expiration = expiration,
ConfirmationToken = value
};
reservedValues.Add(reservedValue);
}
else if (reservedValue.Expiration == null)
{
return reservedValue.OwnerToken == ownerToken;
}
else if (reservedValue.OwnerToken == ownerToken)
{
// if it's the same, extend the lease
reservedValue.Expiration = expiration;
}
else if (reservedValue.Expiration < now)
{
// take ownership if the reserved value has expired
reservedValue.OwnerToken = ownerToken;
reservedValue.Expiration = expiration;
}
else
{
return false;
}
try
{
db.SaveChanges();
return true;
}
catch (Exception exception)
{
if (!exception.IsConcurrencyException())
{
throw;
}
}
return false;
}
}));
}
