com.yahoo.bullet.querying

Class RateLimiter

java.lang.Object

com.yahoo.bullet.querying.RateLimiter

public class RateLimiter
extends Object

This class implements a simple rate checking mechanism. It accepts a maximum and a time window in which the maximum should not be exceeded. Call increment() (or if batching for when what this is counting happens and then call isRateLimited() to check if the rate limit has been reached. You should check if the rate is limited at least once per your given time interval. If you check too late, your counted measure will be averaged over the time duration since the last check, which may or may not cause your rate limit criteria to be violated. This can happen if your increments or adds are bursty so you exceed the rate limit within your time interval but you neglect to check it for a long enough time interval where the burst is spread out over bringing the overall rate lower than your configured maximum and yielding a false negative.

Field Summary

Fields

Modifier and Type	Field and Description
static int	SECOND

Constructor Summary

Constructors

Constructor and Description
RateLimiter(int maximum) Create an instance of this that uses a default time window of SECOND ms.
RateLimiter(int maximum, int timeInterval) Create an instance of this that uses the given maximum and the given time interval.

Method Summary

Modifier and Type	Method and Description
void	add(int n) Increment the measure that this is counting by the given positive number.
double	getCurrentRate() Returns the absolute current rate since the last check interval.
void	increment() Increment the measure that this is counting by one.
boolean	isRateLimited() Checks to see if this is rate limited.

Methods inherited from class java.lang.Object

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

Field Detail

SECOND

public static final int SECOND

See Also:

Constant Field Values

Constructor Detail

RateLimiter

public RateLimiter(int maximum)
            throws IllegalArgumentException

Create an instance of this that uses a default time window of SECOND ms.

Parameters:

maximum - A positive maximum count that this uses as the upper limit per the time interval.

Throws:

IllegalArgumentException - if the maximum was not positive.

RateLimiter

public RateLimiter(int maximum,
                   int timeInterval)
            throws IllegalArgumentException

Create an instance of this that uses the given maximum and the given time interval.

Parameters:

maximum - A positive maximum count that is the limit for each time interval.

timeInterval - The rate check will be done only at most once for this positive time interval in milliseconds.

Throws:

IllegalArgumentException - if the maximum or the time interval were not positive.

Method Detail

increment

public void increment()

Increment the measure that this is counting by one.

add

public void add(int n)

Increment the measure that this is counting by the given positive number.

Parameters:

n - The number to add to the count.

Throws:

IllegalArgumentException - if the given number was not positive.

isRateLimited

public boolean isRateLimited()

Checks to see if this is rate limited. The rate is only checked at most once for each time interval. It is therefore possible to exceed the absolute rate limit momentarily.

Returns:

A boolean denoting whether the rate limit has been exceeded.

getCurrentRate

public double getCurrentRate()

Returns the absolute current rate since the last check interval.

Returns:

A double representing the current absolute rate (per ms).