ExponentialBackOff (google-http-java-client 1.35.0)

java.lang.Object
- com.google.api.client.util.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.
If the time elapsed since an ExponentialBackOff instance is created goes past the max_elapsed_time then the method nextBackOffMillis() starts returning BackOff.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 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              BackOff.STOP
 
```
Implementation is not thread-safe.
Since:

1.15

Author:

Ravi Mistry

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class ExponentialBackOff.Builder
Builder for ExponentialBackOff.

Nested Classes
Modifier and Type	Class and Description
`static class`	`ExponentialBackOff.Builder` Builder for `ExponentialBackOff`.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`DEFAULT_INITIAL_INTERVAL_MILLIS` The default initial interval value in milliseconds (0.5 seconds).
`static int`	`DEFAULT_MAX_ELAPSED_TIME_MILLIS` The default maximum elapsed time in milliseconds (15 minutes).
`static int`	`DEFAULT_MAX_INTERVAL_MILLIS` The default maximum back off time in milliseconds (1 minute).
`static double`	`DEFAULT_MULTIPLIER` The default multiplier value (1.5 which is 50% increase per back off).
`static double`	`DEFAULT_RANDOMIZATION_FACTOR` The default randomization factor (0.5 which results in a random period ranging between 50% below and 50% above the retry interval).

Fields inherited from interface com.google.api.client.util.BackOff
STOP, STOP_BACKOFF, ZERO_BACKOFF

Constructor Summary

Constructors
Modifier	Constructor and Description
	`ExponentialBackOff()` Creates an instance of ExponentialBackOffPolicy using default values.
`protected`	`ExponentialBackOff(ExponentialBackOff.Builder builder)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`getCurrentIntervalMillis()` Returns the current retry interval in milliseconds.
`long`	`getElapsedTimeMillis()` Returns the elapsed time in milliseconds since an `ExponentialBackOff` instance is created and is reset when `reset()` is called.
`int`	`getInitialIntervalMillis()` Returns the initial retry interval in milliseconds.
`int`	`getMaxElapsedTimeMillis()` Returns the maximum elapsed time in milliseconds.
`int`	`getMaxIntervalMillis()` Returns the maximum value of the back off period in milliseconds.
`double`	`getMultiplier()` Returns the value to multiply the current interval with for each retry attempt.
`double`	`getRandomizationFactor()` Returns the randomization factor to use for creating a range around the retry interval.
`long`	`nextBackOffMillis()` Gets the number of milliseconds to wait before retrying the operation or `BackOff.STOP` to indicate that no retries should be made.
`void`	`reset()` Sets the interval back to the initial retry interval and restarts the timer.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DEFAULT_INITIAL_INTERVAL_MILLIS
```
public static final int DEFAULT_INITIAL_INTERVAL_MILLIS
```
    The default initial interval value in milliseconds (0.5 seconds).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_RANDOMIZATION_FACTOR
```
public static final double DEFAULT_RANDOMIZATION_FACTOR
```
    The default randomization factor (0.5 which results in a random period ranging between 50% below and 50% above the retry interval).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MULTIPLIER
```
public static final double DEFAULT_MULTIPLIER
```
    The default multiplier value (1.5 which is 50% increase per back off).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_INTERVAL_MILLIS
```
public static final int DEFAULT_MAX_INTERVAL_MILLIS
```
    The default maximum back off time in milliseconds (1 minute).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_ELAPSED_TIME_MILLIS
```
public static final int DEFAULT_MAX_ELAPSED_TIME_MILLIS
```
    The default maximum elapsed time in milliseconds (15 minutes).
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - 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
  - ExponentialBackOff
```
protected ExponentialBackOff(ExponentialBackOff.Builder builder)
```
    Parameters:
    
    builder - builder
- Method Detail
  - reset
```
public final 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()
                       throws IOException
```
    Gets the number of milliseconds to wait before retrying the operation or BackOff.STOP to indicate that no retries should be made.
    Example usage:
```
 long backOffMillis = backoff.nextBackOffMillis();
 if (backOffMillis == Backoff.STOP) {
 // do not retry operation
 } else {
 // sleep for backOffMillis milliseconds and retry operation
 }
 
```
    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
    
    Throws:
    
    IOException
  - getInitialIntervalMillis
```
public final int getInitialIntervalMillis()
```
    Returns the initial retry interval in milliseconds.
  - getRandomizationFactor
```
public final double getRandomizationFactor()
```
    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.
  - getCurrentIntervalMillis
```
public final int getCurrentIntervalMillis()
```
    Returns the current retry interval in milliseconds.
  - getMultiplier
```
public final double getMultiplier()
```
    Returns the value to multiply the current interval with for each retry attempt.
  - getMaxIntervalMillis
```
public final int getMaxIntervalMillis()
```
    Returns the maximum value of the back off period in milliseconds. Once the current interval reaches this value it stops increasing.
  - getMaxElapsedTimeMillis
```
public final int getMaxElapsedTimeMillis()
```
    Returns the maximum elapsed time in milliseconds.
    If the time elapsed since an ExponentialBackOff instance is created goes past the max_elapsed_time then the method nextBackOffMillis() starts returning BackOff.STOP. The elapsed time can be reset by calling reset().
  - getElapsedTimeMillis
```
public final long getElapsedTimeMillis()
```
    Returns the elapsed time in milliseconds since an ExponentialBackOff instance is created and is reset when reset() is called.
    The elapsed time is computed using System.nanoTime().

Class ExponentialBackOff

Nested Class Summary

Field Summary

Fields inherited from interface com.google.api.client.util.BackOff

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_INITIAL_INTERVAL_MILLIS

DEFAULT_RANDOMIZATION_FACTOR

DEFAULT_MULTIPLIER

DEFAULT_MAX_INTERVAL_MILLIS

DEFAULT_MAX_ELAPSED_TIME_MILLIS

Constructor Detail

ExponentialBackOff

ExponentialBackOff

Method Detail

reset

nextBackOffMillis

getInitialIntervalMillis

getRandomizationFactor

getCurrentIntervalMillis

getMultiplier

getMaxIntervalMillis

getMaxElapsedTimeMillis

getElapsedTimeMillis