opensim-development – Rev 1
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using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using OpenSim.Framework;
using log4net;
namespace OpenSim.Region.ClientStack.LindenUDP
{
/// <summary>
/// A hierarchical token bucket for bandwidth throttling. See
/// http://en.wikipedia.org/wiki/Token_bucket for more information
/// </summary>
public class TokenBucket
{
private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
private static Int32 m_counter = 0;
// private Int32 m_identifier;
/// <summary>
/// Number of ticks (ms) per quantum, drip rate and max burst
/// are defined over this interval.
/// </summary>
protected const Int32 m_ticksPerQuantum = 1000;
/// <summary>
/// This is the number of quantums worth of packets that can
/// be accommodated during a burst
/// </summary>
protected const Double m_quantumsPerBurst = 1.5;
/// <summary>
/// </summary>
protected const Int32 m_minimumDripRate = 1400;
/// <summary>Time of the last drip, in system ticks</summary>
protected Int32 m_lastDrip;
/// <summary>
/// The number of bytes that can be sent at this moment. This is the
/// current number of tokens in the bucket
/// </summary>
protected Int64 m_tokenCount;
/// <summary>
/// Map of children buckets and their requested maximum burst rate
/// </summary>
protected Dictionary<TokenBucket,Int64> m_children = new Dictionary<TokenBucket,Int64>();
#region Properties
/// <summary>
/// The parent bucket of this bucket, or null if this bucket has no
/// parent. The parent bucket will limit the aggregate bandwidth of all
/// of its children buckets
/// </summary>
protected TokenBucket m_parent;
public TokenBucket Parent
{
get { return m_parent; }
set { m_parent = value; }
}
/// <summary>
/// Maximum burst rate in bytes per second. This is the maximum number
/// of tokens that can accumulate in the bucket at any one time. This
/// also sets the total request for leaf nodes
/// </summary>
protected Int64 m_burstRate;
public Int64 RequestedBurstRate
{
get { return m_burstRate; }
set { m_burstRate = (value < 0 ? 0 : value); }
}
public Int64 BurstRate
{
get {
double rate = RequestedBurstRate * BurstRateModifier();
if (rate < m_minimumDripRate * m_quantumsPerBurst)
rate = m_minimumDripRate * m_quantumsPerBurst;
return (Int64) rate;
}
}
/// <summary>
/// The speed limit of this bucket in bytes per second. This is the
/// number of tokens that are added to the bucket per quantum
/// </summary>
/// <remarks>Tokens are added to the bucket any time
/// <seealso cref="RemoveTokens"/> is called, at the granularity of
/// the system tick interval (typically around 15-22ms)</remarks>
protected Int64 m_dripRate;
public virtual Int64 RequestedDripRate
{
get { return (m_dripRate == 0 ? m_totalDripRequest : m_dripRate); }
set {
m_dripRate = (value < 0 ? 0 : value);
m_burstRate = (Int64)((double)m_dripRate * m_quantumsPerBurst);
m_totalDripRequest = m_dripRate;
if (m_parent != null)
m_parent.RegisterRequest(this,m_dripRate);
}
}
public virtual Int64 DripRate
{
get {
if (m_parent == null)
return Math.Min(RequestedDripRate,TotalDripRequest);
double rate = (double)RequestedDripRate * m_parent.DripRateModifier();
if (rate < m_minimumDripRate)
rate = m_minimumDripRate;
return (Int64)rate;
}
}
/// <summary>
/// The current total of the requested maximum burst rates of
/// this bucket's children buckets.
/// </summary>
protected Int64 m_totalDripRequest;
public Int64 TotalDripRequest
{
get { return m_totalDripRequest; }
set { m_totalDripRequest = value; }
}
#endregion Properties
#region Constructor
/// <summary>
/// Default constructor
/// </summary>
/// <param name="parent">Parent bucket if this is a child bucket, or
/// null if this is a root bucket</param>
/// <param name="maxBurst">Maximum size of the bucket in bytes, or
/// zero if this bucket has no maximum capacity</param>
/// <param name="dripRate">Rate that the bucket fills, in bytes per
/// second. If zero, the bucket always remains full</param>
public TokenBucket(TokenBucket parent, Int64 dripRate)
{
// m_identifier = m_counter++;
m_counter++;
Parent = parent;
RequestedDripRate = dripRate;
// TotalDripRequest = dripRate; // this will be overwritten when a child node registers
// MaxBurst = (Int64)((double)dripRate * m_quantumsPerBurst);
m_lastDrip = Util.EnvironmentTickCount();
}
#endregion Constructor
/// <summary>
/// Compute a modifier for the MaxBurst rate. This is 1.0, meaning
/// no modification if the requested bandwidth is less than the
/// max burst bandwidth all the way to the root of the throttle
/// hierarchy. However, if any of the parents is over-booked, then
/// the modifier will be less than 1.
/// </summary>
protected double DripRateModifier()
{
Int64 driprate = DripRate;
return driprate >= TotalDripRequest ? 1.0 : (double)driprate / (double)TotalDripRequest;
}
/// <summary>
/// </summary>
protected double BurstRateModifier()
{
// for now... burst rate is always m_quantumsPerBurst (constant)
// larger than drip rate so the ratio of burst requests is the
// same as the drip ratio
return DripRateModifier();
}
/// <summary>
/// Register drip rate requested by a child of this throttle. Pass the
/// changes up the hierarchy.
/// </summary>
public void RegisterRequest(TokenBucket child, Int64 request)
{
lock (m_children)
{
m_children[child] = request;
// m_totalDripRequest = m_children.Values.Sum();
m_totalDripRequest = 0;
foreach (KeyValuePair<TokenBucket, Int64> cref in m_children)
m_totalDripRequest += cref.Value;
}
// Pass the new values up to the parent
if (m_parent != null)
m_parent.RegisterRequest(this,Math.Min(RequestedDripRate, TotalDripRequest));
}
/// <summary>
/// Remove the rate requested by a child of this throttle. Pass the
/// changes up the hierarchy.
/// </summary>
public void UnregisterRequest(TokenBucket child)
{
lock (m_children)
{
m_children.Remove(child);
// m_totalDripRequest = m_children.Values.Sum();
m_totalDripRequest = 0;
foreach (KeyValuePair<TokenBucket, Int64> cref in m_children)
m_totalDripRequest += cref.Value;
}
// Pass the new values up to the parent
if (m_parent != null)
m_parent.RegisterRequest(this,Math.Min(RequestedDripRate, TotalDripRequest));
}
/// <summary>
/// Remove a given number of tokens from the bucket
/// </summary>
/// <param name="amount">Number of tokens to remove from the bucket</param>
/// <returns>True if the requested number of tokens were removed from
/// the bucket, otherwise false</returns>
public bool RemoveTokens(Int64 amount)
{
// Deposit tokens for this interval
Drip();
// If we have enough tokens then remove them and return
if (m_tokenCount - amount >= 0)
{
// we don't have to remove from the parent, the drip rate is already
// reflective of the drip rate limits in the parent
m_tokenCount -= amount;
return true;
}
return false;
}
/// <summary>
/// Deposit tokens into the bucket from a child bucket that did
/// not use all of its available tokens
/// </summary>
protected void Deposit(Int64 count)
{
m_tokenCount += count;
// Deposit the overflow in the parent bucket, this is how we share
// unused bandwidth
Int64 burstrate = BurstRate;
if (m_tokenCount > burstrate)
m_tokenCount = burstrate;
}
/// <summary>
/// Add tokens to the bucket over time. The number of tokens added each
/// call depends on the length of time that has passed since the last
/// call to Drip
/// </summary>
/// <returns>True if tokens were added to the bucket, otherwise false</returns>
protected void Drip()
{
// This should never happen... means we are a leaf node and were created
// with no drip rate...
if (DripRate == 0)
{
m_log.WarnFormat("[TOKENBUCKET] something odd is happening and drip rate is 0");
return;
}
// Determine the interval over which we are adding tokens, never add
// more than a single quantum of tokens
Int32 deltaMS = Math.Min(Util.EnvironmentTickCountSubtract(m_lastDrip), m_ticksPerQuantum);
m_lastDrip = Util.EnvironmentTickCount();
// This can be 0 in the very unusual case that the timer wrapped
// It can be 0 if we try add tokens at a sub-tick rate
if (deltaMS <= 0)
return;
Deposit(deltaMS * DripRate / m_ticksPerQuantum);
}
}
public class AdaptiveTokenBucket : TokenBucket
{
// private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
/// <summary>
/// The minimum rate for flow control. Minimum drip rate is one
/// packet per second. Open the throttle to 15 packets per second
/// or about 160kbps.
/// </summary>
protected const Int64 m_minimumFlow = m_minimumDripRate * 15;
// <summary>
// The maximum rate for flow control. Drip rate can never be
// greater than this.
// </summary>
protected Int64 m_maxDripRate = 0;
protected Int64 MaxDripRate
{
get { return (m_maxDripRate == 0 ? m_totalDripRequest : m_maxDripRate); }
set { m_maxDripRate = (value == 0 ? 0 : Math.Max(value,m_minimumFlow)); }
}
private bool m_enabled = false;
// <summary>
//
// </summary>
public virtual Int64 AdjustedDripRate
{
get { return m_dripRate; }
set {
m_dripRate = OpenSim.Framework.Util.Clamp<Int64>(value,m_minimumFlow,MaxDripRate);
m_burstRate = (Int64)((double)m_dripRate * m_quantumsPerBurst);
if (m_parent != null)
m_parent.RegisterRequest(this,m_dripRate);
}
}
// <summary>
//
// </summary>
public AdaptiveTokenBucket(TokenBucket parent, Int64 maxDripRate, bool enabled) : base(parent,maxDripRate)
{
m_enabled = enabled;
if (m_enabled)
{
// m_log.DebugFormat("[TOKENBUCKET] Adaptive throttle enabled");
MaxDripRate = maxDripRate;
AdjustedDripRate = m_minimumFlow;
}
}
// <summary>
//
// </summary>
public void ExpirePackets(Int32 count)
{
// m_log.WarnFormat("[ADAPTIVEBUCKET] drop {0} by {1} expired packets",AdjustedDripRate,count);
if (m_enabled)
AdjustedDripRate = (Int64) (AdjustedDripRate / Math.Pow(2,count));
}
// <summary>
//
// </summary>
public void AcknowledgePackets(Int32 count)
{
if (m_enabled)
AdjustedDripRate = AdjustedDripRate + count;
}
}
}