| /* |
| * |
| * 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; |
| } |