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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_connect_timeout, double multiplier,
double jitter, grpc_millis min_timeout_millis,
grpc_millis 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;
}
grpc_millis grpc_backoff_begin(grpc_exec_ctx *exec_ctx, grpc_backoff *backoff) {
backoff->current_timeout_millis = backoff->initial_connect_timeout;
const grpc_millis first_timeout =
GPR_MAX(backoff->current_timeout_millis, backoff->min_timeout_millis);
return grpc_exec_ctx_now(exec_ctx) + first_timeout;
}
/* 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);
}
grpc_millis grpc_backoff_step(grpc_exec_ctx *exec_ctx, grpc_backoff *backoff) {
const double new_timeout_millis =
backoff->multiplier * (double)backoff->current_timeout_millis;
backoff->current_timeout_millis =
GPR_MIN((grpc_millis)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 =
(grpc_millis)((double)(backoff->current_timeout_millis) + jitter);
const grpc_millis current_deadline =
grpc_exec_ctx_now(exec_ctx) + backoff->current_timeout_millis;
const grpc_millis min_deadline =
grpc_exec_ctx_now(exec_ctx) + backoff->min_timeout_millis;
return GPR_MAX(current_deadline, min_deadline);
}
void grpc_backoff_reset(grpc_backoff *backoff) {
backoff->current_timeout_millis = backoff->initial_connect_timeout;
}
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