From f23078cbd302d32649537eedda1769c5685228d8 Mon Sep 17 00:00:00 2001 From: Craig Tiller Date: Fri, 25 Mar 2016 17:07:29 -0700 Subject: Stage #1 of core breakup: move everything under lib --- src/core/lib/support/backoff.c | 76 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 src/core/lib/support/backoff.c (limited to 'src/core/lib/support/backoff.c') diff --git a/src/core/lib/support/backoff.c b/src/core/lib/support/backoff.c new file mode 100644 index 0000000000..4ccfb774ed --- /dev/null +++ b/src/core/lib/support/backoff.c @@ -0,0 +1,76 @@ +/* + * + * 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 + +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; +} -- cgit v1.2.3