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