backoff_algorithm.h File Reference

API for calculating backoff period for retry attempts using exponential backoff with jitter algorithm. This library represents the "Full Jitter" backoff strategy explained in the following document. https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/. More...

#include <stdint.h>

Go to the source code of this file.

Data Structures
struct	BackoffAlgorithmContext_t
	Represents parameters required for calculating the back-off delay for the next retry attempt. More...

Macros
#define	BACKOFF_ALGORITHM_RETRY_FOREVER   ( UINT32_MAX )
	Constant to represent unlimited number of retry attempts.

Enumerations
enum	BackoffAlgorithmStatus_t { BackoffAlgorithmSuccess = 0 , BackoffAlgorithmRetriesExhausted }
	Status for BackoffAlgorithm_GetNextBackoff. More...

Functions
void	BackoffAlgorithm_InitializeParams (BackoffAlgorithmContext_t *pContext, uint16_t backOffBase, uint16_t maxBackOff, uint32_t maxAttempts)
	Initializes the context for using backoff algorithm. The parameters are required for calculating the next retry backoff delay. This function must be called by the application before the first new retry attempt.
BackoffAlgorithmStatus_t	BackoffAlgorithm_GetNextBackoff (BackoffAlgorithmContext_t *pRetryContext, uint32_t randomValue, uint16_t *pNextBackOff)
	Simple exponential backoff and jitter function that provides the delay value for the next retry attempt. After a failure of an operation that needs to be retried, the application should use this function to obtain the backoff delay value for the next retry, and then wait for the backoff time period before retrying the operation.

Detailed Description

API for calculating backoff period for retry attempts using exponential backoff with jitter algorithm. This library represents the "Full Jitter" backoff strategy explained in the following document. https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/.

Function Documentation

BackoffAlgorithm_InitializeParams()

void BackoffAlgorithm_InitializeParams	(	BackoffAlgorithmContext_t *	pContext,
		uint16_t	backOffBase,
		uint16_t	maxBackOff,
		uint32_t	maxAttempts
	)

Initializes the context for using backoff algorithm. The parameters are required for calculating the next retry backoff delay. This function must be called by the application before the first new retry attempt.

Parameters

[out]	pContext	The context to initialize with parameters required for the next backoff delay calculation function.
[in]	maxBackOff	The maximum backoff delay (in milliseconds) between consecutive retry attempts.
[in]	backOffBase	The base value (in milliseconds) of backoff delay to use in the exponential backoff and jitter model.
[in]	maxAttempts	The maximum number of retry attempts. Set the value to BACKOFF_ALGORITHM_RETRY_FOREVER to retry for ever.

BackoffAlgorithm_GetNextBackoff()

BackoffAlgorithmStatus_t BackoffAlgorithm_GetNextBackoff	(	BackoffAlgorithmContext_t *	pRetryContext,
		uint32_t	randomValue,
		uint16_t *	pNextBackOff
	)

Simple exponential backoff and jitter function that provides the delay value for the next retry attempt. After a failure of an operation that needs to be retried, the application should use this function to obtain the backoff delay value for the next retry, and then wait for the backoff time period before retrying the operation.

Parameters

[in,out]	pRetryContext	Structure containing parameters for the next backoff value calculation.
[in]	randomValue	The random value to use for calculation of the backoff period. The random value should be in the range of [0, UINT32_MAX].
[out]	pNextBackOff	This will be populated with the backoff value (in milliseconds) for the next retry attempt. The value does not exceed the maximum backoff delay configured in the context.

Note

For generating a random number, it is recommended to use a Random Number Generator that is seeded with a device-specific entropy source so that possibility of collisions between multiple devices retrying the network operations can be mitigated.

Returns

BackoffAlgorithmSuccess after a successful sleep; BackoffAlgorithmRetriesExhausted when all attempts are exhausted.