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/*
*
* Copyright 2016 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include "src/core/lib/support/backoff.h"
#include <grpc/support/useful.h>
void gpr_backoff_init(gpr_backoff *backoff, int64_t initial_connect_timeout,
double multiplier, double jitter,
int64_t min_timeout_millis, int64_t max_timeout_millis) {
backoff->initial_connect_timeout = initial_connect_timeout;
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->initial_connect_timeout;
const int64_t first_timeout =
GPR_MAX(backoff->current_timeout_millis, backoff->min_timeout_millis);
return gpr_time_add(now, gpr_time_from_millis(first_timeout, 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) {
const double new_timeout_millis =
backoff->multiplier * (double)backoff->current_timeout_millis;
backoff->current_timeout_millis =
GPR_MIN((int64_t)new_timeout_millis, backoff->max_timeout_millis);
const double jitter_range_width = backoff->jitter * new_timeout_millis;
const double jitter =
(2 * generate_uniform_random_number(&backoff->rng_state) - 1) *
jitter_range_width;
backoff->current_timeout_millis =
(int64_t)((double)(backoff->current_timeout_millis) + jitter);
const gpr_timespec current_deadline = gpr_time_add(
now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
const gpr_timespec min_deadline = gpr_time_add(
now, gpr_time_from_millis(backoff->min_timeout_millis, GPR_TIMESPAN));
return gpr_time_max(current_deadline, min_deadline);
}
void gpr_backoff_reset(gpr_backoff *backoff) {
backoff->current_timeout_millis = backoff->initial_connect_timeout;
}
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