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6e9fbeb27c
Summary: We want to keep Env a think layer for better portability. Less platform dependent codes should be moved out of Env. In this patch, I create a wrapper of file readers and writers, and put rate limiting, write buffering, as well as most perf context instrumentation and random kill out of Env. It will make it easier to maintain multiple Env in the future. Test Plan: Run all existing unit tests. Reviewers: anthony, kradhakrishnan, IslamAbdelRahman, yhchiang, igor Reviewed By: igor Subscribers: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D42321
109 lines
3.1 KiB
C++
109 lines
3.1 KiB
C++
// Copyright (c) 2013, 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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#include "db/log_writer.h"
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#include <stdint.h>
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#include "rocksdb/env.h"
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#include "util/coding.h"
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#include "util/crc32c.h"
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#include "util/file_reader_writer.h"
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namespace rocksdb {
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namespace log {
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Writer::Writer(unique_ptr<WritableFileWriter>&& dest)
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: dest_(std::move(dest)), block_offset_(0) {
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for (int i = 0; i <= kMaxRecordType; i++) {
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char t = static_cast<char>(i);
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type_crc_[i] = crc32c::Value(&t, 1);
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}
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}
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Writer::~Writer() {
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}
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Status Writer::AddRecord(const Slice& slice) {
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const char* ptr = slice.data();
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size_t left = slice.size();
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// Fragment the record if necessary and emit it. Note that if slice
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// is empty, we still want to iterate once to emit a single
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// zero-length record
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Status s;
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bool begin = true;
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do {
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const int leftover = kBlockSize - block_offset_;
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assert(leftover >= 0);
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if (leftover < kHeaderSize) {
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// Switch to a new block
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if (leftover > 0) {
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// Fill the trailer (literal below relies on kHeaderSize being 7)
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assert(kHeaderSize == 7);
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dest_->Append(Slice("\x00\x00\x00\x00\x00\x00", leftover));
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}
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block_offset_ = 0;
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}
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// Invariant: we never leave < kHeaderSize bytes in a block.
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assert(static_cast<int>(kBlockSize) - block_offset_ >= kHeaderSize);
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const size_t avail = kBlockSize - block_offset_ - kHeaderSize;
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const size_t fragment_length = (left < avail) ? left : avail;
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RecordType type;
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const bool end = (left == fragment_length);
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if (begin && end) {
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type = kFullType;
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} else if (begin) {
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type = kFirstType;
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} else if (end) {
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type = kLastType;
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} else {
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type = kMiddleType;
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}
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s = EmitPhysicalRecord(type, ptr, fragment_length);
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ptr += fragment_length;
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left -= fragment_length;
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begin = false;
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} while (s.ok() && left > 0);
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return s;
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}
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Status Writer::EmitPhysicalRecord(RecordType t, const char* ptr, size_t n) {
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assert(n <= 0xffff); // Must fit in two bytes
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assert(block_offset_ + kHeaderSize + n <= kBlockSize);
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// Format the header
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char buf[kHeaderSize];
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buf[4] = static_cast<char>(n & 0xff);
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buf[5] = static_cast<char>(n >> 8);
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buf[6] = static_cast<char>(t);
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// Compute the crc of the record type and the payload.
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uint32_t crc = crc32c::Extend(type_crc_[t], ptr, n);
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crc = crc32c::Mask(crc); // Adjust for storage
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EncodeFixed32(buf, crc);
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// Write the header and the payload
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Status s = dest_->Append(Slice(buf, kHeaderSize));
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if (s.ok()) {
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s = dest_->Append(Slice(ptr, n));
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if (s.ok()) {
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s = dest_->Flush();
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}
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}
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block_offset_ += kHeaderSize + n;
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return s;
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}
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} // namespace log
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} // namespace rocksdb
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