Package org.apache.catalina.util

Class TimeBucketCounter

java.lang.Object
org.apache.catalina.util.TimeBucketCounter
public class TimeBucketCounter extends Object
this class maintains a thread safe hash map that has timestamp-based buckets followed by a string for a key, and a counter for a value. each time the increment() method is called it adds the key if it does not exist, increments its value and returns it. a maintenance thread cleans up keys that are prefixed by previous timestamp buckets.

  • Constructor Summary

    Constructors
    Constructor
    Description
    TimeBucketCounter(int bucketDuration)
    Creates a new TimeBucketCounter with the specified lifetime.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    destroy()
    sets isRunning to false to terminate the maintenance thread
    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
    final int
    getCurrentBucketPrefix()
    calculates the current time bucket prefix by shifting bits for fast division, e.g. shift 16 bits is the same as dividing by 65,536 which is about 1:05m
    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. we then multiply the configured requests param by the same ratio in order to compensate for the added time, if any
    final int
    increment(String identifier)
    increments the counter for the passed identifier in the current time bucket and returns the new value

    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)
      Creates a new TimeBucketCounter with the specified lifetime.
      Parameters:
      bucketDuration - duration in seconds, e.g. for 1 minute pass 60

  • Method Details

    • increment

      public final int increment(String identifier)
      increments the counter for the passed identifier in the current time bucket and returns the new value
      Parameters:
      identifier - an identifier for which we want to maintain count, e.g. IP Address
      Returns:
      the count within the current time bucket

    • getCurrentBucketPrefix

      public final int getCurrentBucketPrefix()
      calculates the current time bucket prefix by shifting bits for fast division, e.g. shift 16 bits is the same as dividing by 65,536 which is about 1:05m
      Returns:
      The current bucket prefix.

    • 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

    • 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
      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()
      when we want to test a full bucket duration we need to sleep until the next bucket starts
      Returns:
      the number of milliseconds until the next bucket

    • destroy

      public void destroy()
      sets isRunning to false to terminate the maintenance thread