Class ExponentialBackOffPolicy (1.45.0)

Deprecated. (scheduled to be removed in 1.18). Use HttpBackOffUnsuccessfulResponseHandler with ExponentialBackOff instead.

Beta
Implementation of BackOffPolicy that increases the back off period for each retry attempt using a randomization function that grows exponentially.

#getNextBackOffMillis() is calculated using the following formula:

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

In other words #getNextBackOffMillis() 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.

If the time elapsed since an ExponentialBackOffPolicy instance is created goes past the max_elapsed_time then the method #getNextBackOffMillis() starts returning BackOffPolicy#STOP. The elapsed time can be reset by calling #reset().

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 requests the sequence will be (values in seconds) and assuming we go over the max_elapsed_time on the 10th request:

 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              BackOffPolicy#STOP
 

Implementation is not thread-safe.

The default initial interval value in milliseconds (0.5 seconds).

The default maximum elapsed time in milliseconds (15 minutes).

The default maximum back off time in milliseconds (1 minute).

The default multiplier value (1.5 which is 50% increase per back off).

The default randomization factor (0.5 which results in a random period ranging between 50% below and 50% above the retry interval).

Returns an instance of a new builder.

Creates an instance of ExponentialBackOffPolicy using default values. To override the defaults use #builder.

• initialIntervalMillis is defaulted to #DEFAULT_INITIAL_INTERVAL_MILLIS
• randomizationFactor is defaulted to #DEFAULT_RANDOMIZATION_FACTOR
• multiplier is defaulted to #DEFAULT_MULTIPLIER
• maxIntervalMillis is defaulted to #DEFAULT_MAX_INTERVAL_MILLIS
• maxElapsedTimeMillis is defaulted in #DEFAULT_MAX_ELAPSED_TIME_MILLIS

Returns the current retry interval in milliseconds.

Returns the elapsed time in milliseconds since an ExponentialBackOffPolicy instance is created and is reset when #reset() is called.

The elapsed time is computed using System#nanoTime().

Returns the initial retry interval in milliseconds.

Returns the maximum elapsed time in milliseconds.

If the time elapsed since an ExponentialBackOffPolicy instance is created goes past the max_elapsed_time then the method #getNextBackOffMillis() starts returning BackOffPolicy#STOP. The elapsed time can be reset by calling #reset().

Returns the maximum value of the back off period in milliseconds. Once the current interval reaches this value it stops increasing.

Returns the value to multiply the current interval with for each retry attempt.

Gets the number of milliseconds to wait before retrying an HTTP request. If #STOP is returned, no retries should be made.

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.

Returns the randomization factor to use for creating a range around the retry interval.

A randomization factor of 0.5 results in a random period ranging between 50% below and 50% above the retry interval.

Determines if back off is required based on the specified status code.

The idea is that the servers are only temporarily unavailable, and they should not be overwhelmed when they are trying to get back up.

The default implementation requires back off for 500 and 503 status codes. Subclasses may override if different status codes are required.

Sets the interval back to the initial retry interval and restarts the timer.