Class TimeBucketCounter

java.lang.Object

org.apache.catalina.util.TimeBucketCounterBase

org.apache.catalina.util.TimeBucketCounter

public class TimeBucketCounter
extends TimeBucketCounterBase

A fast counter that optimizes efficiency at the expense of approximate bucket indexing.

Constructor Summary

Constructors

Constructor	Description
TimeBucketCounter(int bucketDuration, ScheduledExecutorService executorService)

Method Summary

Modifier and Type	Method	Description
protected static int	determineShiftBitsOfDuration(int duration)	Determines the bits of shift for the specific bucket duration in seconds, which used to figure out the correct bucket index.
int	getActualDuration()	The actual duration may differ from the configured duration because it is set to the next power of 2 value in order to perform very fast bit shift arithmetic.
long	getBucketIndex(long timestamp)	Calculate the bucket index for the specific timestamp.
long	getMillisUntilNextBucket()	When we want to test a full bucket duration we need to sleep until the next bucket starts.
int	getNumBits()
double	getRatio()	Returns the ratio between the configured duration param and the actual duration which will be set to the next power of 2.

Methods inherited from class org.apache.catalina.util.TimeBucketCounterBase

destroy, genKey, genKey, getBucketDuration, getCurrentBucketPrefix, increment, periodicEvict

Methods inherited from class java.lang.Object

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

Constructor Details

TimeBucketCounter

public TimeBucketCounter(int bucketDuration,
 ScheduledExecutorService executorService)

Method Details

getBucketIndex

public long getBucketIndex(long timestamp)

Calculate the bucket index for the specific timestamp.

Calculates the current time bucket index by shifting bits for fast division, e.g. shift 16 bits is the same as dividing by 65,536 which is about 1:05m.

Specified by:

getBucketIndex in class TimeBucketCounterBase

Parameters:

timestamp - the specific timestamp in milliseconds

Returns:

prefix the bucket key prefix for the specific timestamp

getNumBits

public int getNumBits()

getActualDuration

public int getActualDuration()

The actual duration may differ from the configured duration because it is set to the next power of 2 value in order to perform very fast bit shift arithmetic.

Returns:

the actual bucket duration in milliseconds

determineShiftBitsOfDuration

protected static int determineShiftBitsOfDuration(int duration)

Determines the bits of shift for the specific bucket duration in seconds, which used to figure out the correct bucket index.

Parameters:

duration - bucket duration in seconds

Returns:

bits to be shifted

getRatio

public double getRatio()

Returns the ratio between the configured duration param and the actual duration which will be set to the next power of 2. We then multiply the configured requests param by the same ratio in order to compensate for the added time, if any.

Specified by:

getRatio in class TimeBucketCounterBase

Returns:

the ratio, e.g. 1.092 if the actual duration is 65_536 for the configured duration of 60_000

getMillisUntilNextBucket

public long getMillisUntilNextBucket()

Description copied from class: TimeBucketCounterBase

When we want to test a full bucket duration we need to sleep until the next bucket starts.

WARNING: This method is used for test purpose.

Specified by:

getMillisUntilNextBucket in class TimeBucketCounterBase

Returns:

the number of milliseconds until the next bucket