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/*
* backoffAlgorithm v1.0.0
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/**
* @file backoff_algorithm.c
* @brief Implementation of the backoff algorithm API for a "Full Jitter" exponential backoff
* with jitter strategy.
*/
/* Standard includes. */
#include <assert.h>
#include <stddef.h>
/* Include API header. */
#include "backoff_algorithm.h"
/*-----------------------------------------------------------*/
BackoffAlgorithmStatus_t BackoffAlgorithm_GetNextBackoff( BackoffAlgorithmContext_t * pRetryContext,
uint32_t randomValue,
uint16_t * pNextBackOff )
{
BackoffAlgorithmStatus_t status = BackoffAlgorithmSuccess;
assert( pRetryContext != NULL );
assert( pNextBackOff != NULL );
/* If BACKOFF_ALGORITHM_RETRY_FOREVER is set to 0, try forever. */
if( ( pRetryContext->attemptsDone < pRetryContext->maxRetryAttempts ) ||
( pRetryContext->maxRetryAttempts == BACKOFF_ALGORITHM_RETRY_FOREVER ) )
{
/* The next backoff value is a random value between 0 and the maximum jitter value
* for the retry attempt. */
/* Choose a random value for back-off time between 0 and the max jitter value. */
*pNextBackOff = ( uint16_t ) ( randomValue % ( pRetryContext->nextJitterMax + 1U ) );
/* Increment the retry attempt. */
pRetryContext->attemptsDone++;
/* Double the max jitter value for the next retry attempt, only
* if the new value will be less than the max backoff time value. */
if( pRetryContext->nextJitterMax < ( pRetryContext->maxBackoffDelay / 2U ) )
{
pRetryContext->nextJitterMax += pRetryContext->nextJitterMax;
}
else
{
pRetryContext->nextJitterMax = pRetryContext->maxBackoffDelay;
}
}
else
{
/* When max retry attempts are exhausted, let application know by
* returning BackoffAlgorithmRetriesExhausted. Application may choose to
* restart the retry process after calling BackoffAlgorithm_InitializeParams(). */
status = BackoffAlgorithmRetriesExhausted;
}
return status;
}
/*-----------------------------------------------------------*/
void BackoffAlgorithm_InitializeParams( BackoffAlgorithmContext_t * pContext,
uint16_t backOffBase,
uint16_t maxBackOff,
uint32_t maxAttempts )
{
assert( pContext != NULL );
/* Initialize the context with parameters used in calculating the backoff
* value for the next retry attempt. */
pContext->nextJitterMax = backOffBase;
pContext->maxBackoffDelay = maxBackOff;
pContext->maxRetryAttempts = maxAttempts;
/* The total number of retry attempts is zero at initialization. */
pContext->attemptsDone = 0;
}
/*-----------------------------------------------------------*/