65 lines
2.8 KiB
C++
65 lines
2.8 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include "rocksdb/env.h"
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namespace rocksdb {
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class RateLimiter {
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public:
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virtual ~RateLimiter() {}
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// This API allows user to dynamically change rate limiter's bytes per second.
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// REQUIRED: bytes_per_second > 0
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virtual void SetBytesPerSecond(int64_t bytes_per_second) = 0;
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// Request for token to write bytes. If this request can not be satisfied,
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// the call is blocked. Caller is responsible to make sure
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// bytes <= GetSingleBurstBytes()
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virtual void Request(const int64_t bytes, const Env::IOPriority pri) = 0;
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// Max bytes can be granted in a single burst
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virtual int64_t GetSingleBurstBytes() const = 0;
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// Total bytes that go though rate limiter
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virtual int64_t GetTotalBytesThrough(
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const Env::IOPriority pri = Env::IO_TOTAL) const = 0;
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// Total # of requests that go though rate limiter
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virtual int64_t GetTotalRequests(
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const Env::IOPriority pri = Env::IO_TOTAL) const = 0;
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};
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// Create a RateLimiter object, which can be shared among RocksDB instances to
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// control write rate of flush and compaction.
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// @rate_bytes_per_sec: this is the only parameter you want to set most of the
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// time. It controls the total write rate of compaction and flush in bytes per
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// second. Currently, RocksDB does not enforce rate limit for anything other
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// than flush and compaction, e.g. write to WAL.
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// @refill_period_us: this controls how often tokens are refilled. For example,
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// when rate_bytes_per_sec is set to 10MB/s and refill_period_us is set to
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// 100ms, then 1MB is refilled every 100ms internally. Larger value can lead to
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// burstier writes while smaller value introduces more CPU overhead.
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// The default should work for most cases.
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// @fairness: RateLimiter accepts high-pri requests and low-pri requests.
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// A low-pri request is usually blocked in favor of hi-pri request. Currently,
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// RocksDB assigns low-pri to request from compaciton and high-pri to request
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// from flush. Low-pri requests can get blocked if flush requests come in
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// continuouly. This fairness parameter grants low-pri requests permission by
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// 1/fairness chance even though high-pri requests exist to avoid starvation.
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// You should be good by leaving it at default 10.
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extern RateLimiter* NewGenericRateLimiter(
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int64_t rate_bytes_per_sec,
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int64_t refill_period_us = 100 * 1000,
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int32_t fairness = 10);
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} // namespace rocksdb
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