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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/backoff/backoff.h"
#include <grpc/support/useful.h>
void grpc_backoff_init(grpc_backoff *backoff, grpc_millis initial_backoff,
double multiplier, double jitter,
grpc_millis min_connect_timeout,
grpc_millis max_backoff) {
backoff->initial_backoff = initial_backoff;
backoff->multiplier = multiplier;
backoff->jitter = jitter;
backoff->min_connect_timeout = min_connect_timeout;
backoff->max_backoff = max_backoff;
backoff->rng_state = (uint32_t)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
}
grpc_backoff_result grpc_backoff_begin(grpc_exec_ctx *exec_ctx,
grpc_backoff *backoff) {
backoff->current_backoff = backoff->initial_backoff;
const grpc_millis initial_timeout =
GPR_MAX(backoff->initial_backoff, backoff->min_connect_timeout);
const grpc_millis now = grpc_exec_ctx_now(exec_ctx);
const grpc_backoff_result result = {now + initial_timeout,
now + backoff->current_backoff};
return result;
}
/* 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);
}
static double generate_uniform_random_number_between(uint32_t *rng_state,
double a, double b) {
if (a == b) return a;
if (a > b) GPR_SWAP(double, a, b); // make sure a < b
const double range = b - a;
return a + generate_uniform_random_number(rng_state) * range;
}
grpc_backoff_result grpc_backoff_step(grpc_exec_ctx *exec_ctx,
grpc_backoff *backoff) {
backoff->current_backoff = (grpc_millis)(GPR_MIN(
backoff->current_backoff * backoff->multiplier, backoff->max_backoff));
const double jitter = generate_uniform_random_number_between(
&backoff->rng_state, -backoff->jitter * backoff->current_backoff,
backoff->jitter * backoff->current_backoff);
const grpc_millis current_timeout =
GPR_MAX((grpc_millis)(backoff->current_backoff + jitter),
backoff->min_connect_timeout);
const grpc_millis next_timeout = GPR_MIN(
(grpc_millis)(backoff->current_backoff + jitter), backoff->max_backoff);
const grpc_millis now = grpc_exec_ctx_now(exec_ctx);
const grpc_backoff_result result = {now + current_timeout,
now + next_timeout};
return result;
}
void grpc_backoff_reset(grpc_backoff *backoff) {
backoff->current_backoff = backoff->initial_backoff;
}
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