| /* |
| * |
| * Copyright 2016, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| */ |
| |
| #include "src/core/support/backoff.h" |
| |
| #include <grpc/support/useful.h> |
| |
| void gpr_backoff_init(gpr_backoff *backoff, double multiplier, double jitter, |
| int64_t min_timeout_millis, int64_t max_timeout_millis) { |
| 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->min_timeout_millis; |
| return gpr_time_add( |
| now, gpr_time_from_millis(backoff->current_timeout_millis, 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) { |
| double new_timeout_millis = |
| backoff->multiplier * (double)backoff->current_timeout_millis; |
| double jitter_range = backoff->jitter * new_timeout_millis; |
| double jitter = |
| (2 * generate_uniform_random_number(&backoff->rng_state) - 1) * |
| jitter_range; |
| backoff->current_timeout_millis = |
| GPR_CLAMP((int64_t)(new_timeout_millis + jitter), |
| backoff->min_timeout_millis, backoff->max_timeout_millis); |
| return gpr_time_add( |
| now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN)); |
| } |
| |
| void gpr_backoff_reset(gpr_backoff *backoff) { |
| // forces step() to return a timeout of min_timeout_millis |
| backoff->current_timeout_millis = 0; |
| } |