/// <summary>
/// Attempt to consume a specified number of tokens from the bucket. If the tokens were consumed then <code>true</code>
/// is returned, otherwise <code>false</code> is returned.
/// </summary>
/// <param name="numTokens">The number of tokens to consume from the bucket, must be a positive number.</param>
/// <returns><code>true</code> if the tokens were consumed, <code>false</code> otherwise.</returns>
public bool TryConsume(long numTokens)
{
if (numTokens <= 0)
{
throw new ArgumentOutOfRangeException("numTokens", "Number of tokens to consume must be positive");
}
if (numTokens > _capacity)
{
throw new ArgumentOutOfRangeException("numTokens", "Number of tokens to consume must be less than the capacity of the bucket.");
}
lock (_syncRoot)
{
// Give the refill strategy a chance to add tokens if it needs to, but beware of overflow
var newTokens = Math.Min(_capacity, Math.Max(0, _refillStrategy.Refill()));
_size = Math.Max(0, Math.Min(_size + newTokens, _capacity));
if (numTokens > _size)
{
return(false);
}
// Now try to consume some tokens
_size -= numTokens;
return(true);
}
}
/// <summary>
/// Attempts to consume the specified number of tokens from the bucket. If the
/// requested number of tokens are not immediately available, then this method
/// will return false to indicate that zero tokens have been consumed.
/// </summary>
public bool TryConsume(long tokens)
{
if (tokens <= 0)
{
throw new ArgumentOutOfRangeException(nameof(tokens),
"Number of tokens to consume must be positive"
);
}
if (tokens > Capacity)
{
throw new ArgumentOutOfRangeException(nameof(tokens),
"Number of tokens to consume must be less than or equal to the capacity"
);
}
lock (_sync)
{
// determine how many units have become available since last invocation
var refilled = Math.Max(0, _refill.Refill());
// the number of tokens to add, the max of which is the difference between capacity and currently available
var deltaTokens = Math.Min(Capacity - _available, refilled);
// update the available number of units with the new tokens
_available += deltaTokens;
if (tokens > _available)
{
// we don't have enough tokens yet
Logging.Log.Trace($"LeakyBucket.TryConsume({tokens}): Failed to consumed tokens. Available: {_available}");
return(false);
}
// subtract the number of tokens consumed
_available = _available - tokens;
Logging.Log.Trace($"LeakyBucket.TryConsume({tokens}): Successfully consumed tokens. Available: {_available}");
return(true);
}
}
/// <summary>
/// Sometimes the bucket is half-used before we start counting. This allows us
/// to account for this in the beginning.
/// </summary>
public void SetRemainingTokens(long numTokens)
{
lock (_syncRoot)
_refillStrategy.Refill();
_size = numTokens;
}
