Package org.telegram.telegrambots.longpolling.util

Class ExponentialBackOff

Object
ExponentialBackOff
All Implemented Interfaces:
BackOff
public class ExponentialBackOff extends Object implements BackOff
Implementation of BackOff that increases the back off period for each retry attempt using a randomization function that grows exponentially.

nextBackOffMillis() is calculated using the following formula: 

 randomized_interval =
 retry_interval * (random value in range [1 - randomization_factor, 1 + randomization_factor])

In other words nextBackOffMillis() will range between the randomization factor percentage below and above the retry interval. For example, using 2 seconds as the base retry interval and 0.5 as the randomization factor, the actual back off period used in the next retry attempt will be between 1 and 3 seconds.

Note: max_interval caps the retry_interval and not the randomized_interval.

Example: The default retry_interval is .5 seconds, default randomization_factor is 0.5, default multiplier is 1.5 and the default max_interval is 1 minute. For 10 tries the sequence will be (values in seconds) and assuming we go over the max_elapsed_time on the 10th try: 

 request#     retry_interval     randomized_interval

 1             0.5                [0.25,   0.75]
 2             0.75               [0.375,  1.125]
 3             1.125              [0.562,  1.687]
 4             1.687              [0.8435, 2.53]
 5             2.53               [1.265,  3.795]
 6             3.795              [1.897,  5.692]
 7             5.692              [2.846,  8.538]
 8             8.538              [4.269, 12.807]
 9            12.807              [6.403, 19.210]
 10           19.210              maxElapsedTimeMillis

Implementation is not thread-safe.

Since:
1.15
Author:
Ravi Mistry

  • Constructor Details

    • ExponentialBackOff

      public ExponentialBackOff()
      Creates an instance of ExponentialBackOffPolicy using default values.

      To override the defaults use ExponentialBackOff.Builder.

      • initialIntervalMillis defaults to DEFAULT_INITIAL_INTERVAL_MILLIS
      • randomizationFactor defaults to DEFAULT_RANDOMIZATION_FACTOR
      • multiplier defaults to DEFAULT_MULTIPLIER
      • maxIntervalMillis defaults to DEFAULT_MAX_INTERVAL_MILLIS
      • maxElapsedTimeMillis defaults in DEFAULT_MAX_ELAPSED_TIME_MILLIS

  • Method Details

    • reset

      public void reset()
      Sets the interval back to the initial retry interval and restarts the timer.
      Specified by:
      reset in interface BackOff

    • nextBackOffMillis

      public long nextBackOffMillis()
      specify the next backoff interval in milliseconds

      This method calculates the next back off interval using the formula: randomized_interval = retry_interval +/- (randomization_factor * retry_interval)

      Subclasses may override if a different algorithm is required.

      Specified by:
      nextBackOffMillis in interface BackOff