Package com.linkedin.venice.throttle

Class TokenBucket

java.lang.Object

com.linkedin.venice.throttle.TokenBucket

All Implemented Interfaces:

VeniceRateLimiter

public class TokenBucket
extends java.lang.Object
implements VeniceRateLimiter

See Also:

Token Bucket on Wikipedia This implementation aims to be very high performance with the goal of supporting a very large number of TokenBuckets in an application; thus avoiding an auxilliary thread to refill the bucket.

Nested Class Summary

Nested classes/interfaces inherited from interface com.linkedin.venice.throttle.VeniceRateLimiter

VeniceRateLimiter.RateLimiterType

Constructor Summary

Constructors

Constructor	Description
TokenBucket(long capacity, long refillAmount, long refillInterval, java.util.concurrent.TimeUnit refillUnit, java.time.Clock clock)	This constructor should only be used by tests.

Method Summary

Modifier and Type	Method	Description
float	getAmortizedRefillPerSecond()
long	getCapacity()
long	getEnforcementInterval()
long	getQuota()
long	getRefillAmount()
long	getStaleTokenCount()	This method does not call #update(), so it is only accurate as of the last time #tryConsume() was called
double	getStaleUsageRatio()
void	setQuota(long quota)	The following methods are used only when checking if the new quota requests are different from the existing quota.
static TokenBucket	tokenBucketFromRcuPerSecond(long totalRcuPerSecond, double thisBucketProportionOfTotalRcu, long enforcementIntervalMilliseconds, int enforcementCapacityMultiple, java.time.Clock clock)
java.lang.String	toString()
boolean	tryAcquirePermit(int units)	Try to acquire permit for the given rcu.
boolean	tryConsume(long tokensToConsume)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

TokenBucket

public TokenBucket(long capacity,
                   long refillAmount,
                   long refillInterval,
                   java.util.concurrent.TimeUnit refillUnit,
                   java.time.Clock clock)

This constructor should only be used by tests. Application should not specify it's own instance of Clock

Parameters:

capacity -

refillAmount -

refillInterval -

refillUnit -

clock -

Method Detail

getStaleTokenCount

public long getStaleTokenCount()

This method does not call #update(), so it is only accurate as of the last time #tryConsume() was called

Returns:

number of tokens remaining in the bucket

tryConsume

public boolean tryConsume(long tokensToConsume)

getAmortizedRefillPerSecond

public float getAmortizedRefillPerSecond()

getStaleUsageRatio

public double getStaleUsageRatio()

tryAcquirePermit

public boolean tryAcquirePermit(int units)

Description copied from interface: VeniceRateLimiter

Try to acquire permit for the given rcu. Will not block if permit is not available.

Specified by:

tryAcquirePermit in interface VeniceRateLimiter

Parameters:

units - Number of units to acquire.

Returns:

true if permit is acquired, false otherwise.

tokenBucketFromRcuPerSecond

public static TokenBucket tokenBucketFromRcuPerSecond(long totalRcuPerSecond,
                                                      double thisBucketProportionOfTotalRcu,
                                                      long enforcementIntervalMilliseconds,
                                                      int enforcementCapacityMultiple,
                                                      java.time.Clock clock)

Parameters:

totalRcuPerSecond - Number of units per second to allow

thisBucketProportionOfTotalRcu - For maximum fidelity of calculations. If you need a smaller portion of the RCU to be applied then set this to an appropriate multiplier. Otherwise set this to 1.

Returns:

See Also:

for an explanation of TokenBucket capacity, refill amount, and refill interval This method takes a rate in units per second, and scales it according to the desired refill interval in milliseconds, and the multiple of refill we wish to use for capacity. Since the resulting token bucket must have a whole number of tokens in its refill amount and capacity, if we only accept one parameter in this method (localRcuPerSecond) then we might have suboptimal results given integer division. For example, with a global rate of 1 Rcu per second, and a proportion of 0.1, along with an enforcement interval of 10 seconds (10000 milliseconds), we would be forced to pass 1 localRcuPerSecond, which is 10x the desired quota. By passing both the global rate of 1 Rcu per second and a desired proportion, this method can multiply by the enforcement interval first before shrinking by the proportion, allowing the Bucket to be configured with the correct 1 refill every 10 seconds.

setQuota

public void setQuota(long quota)

Description copied from interface: VeniceRateLimiter

The following methods are used only when checking if the new quota requests are different from the existing quota.

Specified by:

setQuota in interface VeniceRateLimiter

getQuota

public long getQuota()

Specified by:

getQuota in interface VeniceRateLimiter

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getCapacity

public long getCapacity()

getRefillAmount

public long getRefillAmount()

getEnforcementInterval

public long getEnforcementInterval()