com.amazonaws.internal

Class TokenBucket

java.lang.Object

com.amazonaws.internal.TokenBucket

public class TokenBucket
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	TokenBucket.Clock

Constructor Summary

Constructors

Constructor and Description
TokenBucket()

Method Summary

Modifier and Type	Method and Description
boolean	acquire(double amount) Acquire tokens from the bucket.
boolean	acquire(double amount, boolean fastFail) Acquire tokens from the bucket.
void	updateClientSendingRate(boolean throttlingResponse) _UpdateClientSendingRate(response) _UpdateMeasuredRate() if IsThrottlingError(response) if not enabled rate_to_use = measured_tx_rate else rate_to_use = min(measured_tx_rate, fill_rate) # The fill_rate is from the token bucket.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TokenBucket

public TokenBucket()

Method Detail

acquire

public boolean acquire(double amount)

Acquire tokens from the bucket. If the bucket contains enough capacity to satisfy the request, this method will return immediately, otherwise the method will block the calling thread until enough tokens are refilled.

 _TokenBucketAcquire(amount)
   # Client side throttling is not enabled until we see a throttling error.
   if not enabled
     return

   _TokenBucketRefill()
   # Next see if we have enough capacity for the requested amount.
   if amount <= current_capacity
     current_capacity = current_capacity - amount
   else
     sleep((amount - current_capacity) / fill_rate)
     current_capacity = current_capacity - amount
   return
 

This is equivalent to acquire(amount, false).

Parameters:

amount - The amount of tokens to acquire.

Returns:

Whether the amount was successfully acquired.

acquire

public boolean acquire(double amount,
                       boolean fastFail)

Acquire tokens from the bucket. If the bucket contains enough capacity to satisfy the request, this method will return immediately. Otherwise, the behavior depends on the value of fastFail. If it is true, then it will return false immediately, signaling that enough capacity could not be acquired. Otherwise if fastFail is false, then it will wait the required amount of time to fill the bucket with enough tokens to satisfy amount.

 _TokenBucketAcquire(amount)
   # Client side throttling is not enabled until we see a throttling error.
   if not enabled
     return

   _TokenBucketRefill()
   # Next see if we have enough capacity for the requested amount.
   if amount <= current_capacity
     current_capacity = current_capacity - amount
   else
     sleep((amount - current_capacity) / fill_rate)
     current_capacity = current_capacity - amount
   return
 

Parameters:

amount - The amount of tokens to acquire.

fastFail - Whether this method should return immediately instead of waiting if amount exceeds the current capacity.

Returns:

Whether the amount was successfully acquired.

updateClientSendingRate

public void updateClientSendingRate(boolean throttlingResponse)

 _UpdateClientSendingRate(response)
   _UpdateMeasuredRate()

   if IsThrottlingError(response)
     if not enabled
       rate_to_use = measured_tx_rate
     else
       rate_to_use = min(measured_tx_rate, fill_rate)

     # The fill_rate is from the token bucket.
     last_max_rate = rate_to_use
     _CalculateTimeWindow()
     last_throttle_time = time()
     calculated_rate = _CUBICThrottle(rate_to_use)
     TokenBucketEnable()
   else
     _CalculateTimeWindow()
     calculated_rate = _CUBICSuccess(time())

   new_rate = min(calculated_rate, 2 * measured_tx_rate)
   _TokenBucketUpdateRate(new_rate)