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/*
*
* Copyright 2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include "src/core/lib/support/backoff.h"
#include <grpc/support/useful.h>
void gpr_backoff_init(gpr_backoff *backoff, double multiplier, double jitter,
int64_t min_timeout_millis, int64_t max_timeout_millis) {
backoff->multiplier = multiplier;
backoff->jitter = jitter;
backoff->min_timeout_millis = min_timeout_millis;
backoff->max_timeout_millis = max_timeout_millis;
backoff->rng_state = (uint32_t)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
}
gpr_timespec gpr_backoff_begin(gpr_backoff *backoff, gpr_timespec now) {
backoff->current_timeout_millis = backoff->min_timeout_millis;
return gpr_time_add(
now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
}
/* Generate a random number between 0 and 1. */
static double generate_uniform_random_number(uint32_t *rng_state) {
*rng_state = (1103515245 * *rng_state + 12345) % ((uint32_t)1 << 31);
return *rng_state / (double)((uint32_t)1 << 31);
}
gpr_timespec gpr_backoff_step(gpr_backoff *backoff, gpr_timespec now) {
double new_timeout_millis =
backoff->multiplier * (double)backoff->current_timeout_millis;
double jitter_range = backoff->jitter * new_timeout_millis;
double jitter =
(2 * generate_uniform_random_number(&backoff->rng_state) - 1) *
jitter_range;
backoff->current_timeout_millis =
GPR_CLAMP((int64_t)(new_timeout_millis + jitter),
backoff->min_timeout_millis, backoff->max_timeout_millis);
return gpr_time_add(
now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
}
void gpr_backoff_reset(gpr_backoff *backoff) {
// forces step() to return a timeout of min_timeout_millis
backoff->current_timeout_millis = 0;
}
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