The C based gRPC (C++, Python, Ruby, Objective-C, PHP, C#)
https://grpc.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
78 lines
2.4 KiB
78 lines
2.4 KiB
/* |
|
* |
|
* 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 <grpc/support/port_platform.h> |
|
|
|
#include "src/core/lib/backoff/backoff.h" |
|
|
|
#include <algorithm> |
|
|
|
#include "src/core/lib/gpr/useful.h" |
|
|
|
namespace grpc_core { |
|
|
|
namespace { |
|
|
|
/* Generate a random number between 0 and 1. We roll our own RNG because seeding |
|
* rand() modifies a global variable we have no control over. */ |
|
double generate_uniform_random_number(uint32_t* rng_state) { |
|
constexpr uint32_t two_raise_31 = uint32_t(1) << 31; |
|
*rng_state = (1103515245 * *rng_state + 12345) % two_raise_31; |
|
return *rng_state / static_cast<double>(two_raise_31); |
|
} |
|
|
|
double generate_uniform_random_number_between(uint32_t* rng_state, double a, |
|
double b) { |
|
if (a == b) return a; |
|
if (a > b) std::swap(a, b); // make sure a < b |
|
const double range = b - a; |
|
return a + generate_uniform_random_number(rng_state) * range; |
|
} |
|
|
|
} // namespace |
|
|
|
BackOff::BackOff(const Options& options) |
|
: options_(options), |
|
rng_state_(static_cast<uint32_t>(gpr_now(GPR_CLOCK_REALTIME).tv_nsec)) { |
|
Reset(); |
|
} |
|
|
|
grpc_millis BackOff::NextAttemptTime() { |
|
if (initial_) { |
|
initial_ = false; |
|
return current_backoff_ + ExecCtx::Get()->Now(); |
|
} |
|
current_backoff_ = static_cast<grpc_millis>( |
|
std::min(current_backoff_ * options_.multiplier(), |
|
static_cast<double>(options_.max_backoff()))); |
|
const double jitter = generate_uniform_random_number_between( |
|
&rng_state_, -options_.jitter() * current_backoff_, |
|
options_.jitter() * current_backoff_); |
|
const grpc_millis next_timeout = |
|
static_cast<grpc_millis>(current_backoff_ + jitter); |
|
return next_timeout + ExecCtx::Get()->Now(); |
|
} |
|
|
|
void BackOff::Reset() { |
|
current_backoff_ = options_.initial_backoff(); |
|
initial_ = true; |
|
} |
|
|
|
void BackOff::SetRandomSeed(uint32_t seed) { rng_state_ = seed; } |
|
|
|
} // namespace grpc_core
|
|
|