Package io.hekate.messaging.retry

Class ExponentialBackoffPolicy

  • All Implemented Interfaces:
    RetryBackoffPolicy
    public class ExponentialBackoffPolicy
extends Object
implements RetryBackoffPolicy
    A backoff policy that waits exponentially longer between each attempt (but keeps a constant delay once a maximum delay is reached).

    This policy uses the following formula to calculate the backoff delay: 

    
   (2 ^ (attempt -1)) * baseDelay

    Note: for the very first attempt the answer is always 0 (i.e. retry immediately).

    Parameters of this policy are:

    • BaseDelay - multiplier for each attempt
    • MaxDelay - maximum delay (calculated delay will never exceed this value)

    Examples of calculations: 

    
 BaseDelay: 10  MaxDelay: 3000
 -------------------------------
  Attempt 0  -> 0
  Attempt 1  -> 10
  Attempt 2  -> 20
  Attempt 3  -> 40
  Attempt 4  -> 80
  Attempt 5  -> 160
  Attempt 6  -> 320
  Attempt 7  -> 640
  Attempt 8  -> 1280
  Attempt 9  -> 2560
  Attempt 10 -> 3000
  ...        -> 3000
 
    
 BaseDelay: 500  MaxDelay: 30000
 -------------------------------
  Attempt 0 -> 0
  Attempt 1 -> 500
  Attempt 2 -> 1000
  Attempt 3 -> 2000
  Attempt 4 -> 4000
  Attempt 5 -> 8000
  Attempt 6 -> 16000
  Attempt 7 -> 30000
  ...       -> 30000

    • Field Detail

      • DEFAULT_BASE_DELAY

        public static final long DEFAULT_BASE_DELAY
        Default base delay (=50L) in milliseconds.
        See Also:
        Constant Field Values

      • DEFAULT_MAX_DELAY

        public static final long DEFAULT_MAX_DELAY
        Default maximum delay (=3000L) in milliseconds.
        See Also:
        Constant Field Values

    • Constructor Detail

      • ExponentialBackoffPolicy

        public ExponentialBackoffPolicy​(long baseDelay,
                                long maxDelay)
        Constructs a new instance.
        Parameters:
        baseDelay - Multiplier for each attempt (in milliseconds).
        maxDelay - Maximum delay in milliseconds (calculated delay will never exceed this value).

    • Method Detail

      • baseDelay

        public long baseDelay()
        Returns the base delay of this policy in milliseconds.
        Returns:
        Base delay in milliseconds.

      • maxDelay

        public long maxDelay()
        Returns the maximum delay of this policy in milliseconds.
        Returns:
        Maximum delay in milliseconds.

      • delayBeforeRetry

        public long delayBeforeRetry​(int attempt)
        Description copied from interface: RetryBackoffPolicy
        Returns a delay in milliseconds before the next retry attempt.
        Specified by:
        delayBeforeRetry in interface RetryBackoffPolicy
        Parameters:
        attempt - Attempt (starting with zero for the very first attempt).
        Returns:
        Delay in milliseconds.