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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#ifndef ROCKSDB_LITE
#include <list>
#include <memory>
#include <string>
#include <vector>
#include "rocksdb/comparator.h"
#include "rocksdb/env.h"
#include "utilities/persistent_cache/block_cache_tier_file_buffer.h"
#include "utilities/persistent_cache/lrulist.h"
#include "utilities/persistent_cache/persistent_cache_tier.h"
#include "utilities/persistent_cache/persistent_cache_util.h"
#include "port/port.h"
#include "util/crc32c.h"
#include "util/file_reader_writer.h"
#include "util/mutexlock.h"
// The io code path of persistent cache uses pipelined architecture
//
// client -> In Queue <-- BlockCacheTier --> Out Queue <-- Writer <--> Kernel
//
// This would enable the system to scale for GB/s of throughput which is
// expected with modern devies like NVM.
//
// The file level operations are encapsulated in the following abstractions
//
// BlockCacheFile
// ^
// |
// |
// RandomAccessCacheFile (For reading)
// ^
// |
// |
// WriteableCacheFile (For writing)
//
// Write IO code path :
//
namespace rocksdb {
class WriteableCacheFile;
struct BlockInfo;
// Represents a logical record on device
//
// (L)ogical (B)lock (Address = { cache-file-id, offset, size }
struct LogicalBlockAddress {
LogicalBlockAddress() {}
explicit LogicalBlockAddress(const uint32_t cache_id, const uint32_t off,
const uint16_t size)
: cache_id_(cache_id), off_(off), size_(size) {}
uint32_t cache_id_ = 0;
uint32_t off_ = 0;
uint32_t size_ = 0;
};
typedef LogicalBlockAddress LBA;
// class Writer
//
// Writer is the abstraction used for writing data to file. The component can be
// multithreaded. It is the last step of write pipeline
class Writer {
public:
explicit Writer(PersistentCacheTier* const cache) : cache_(cache) {}
virtual ~Writer() {}
// write buffer to file at the given offset
virtual void Write(WritableFile* const file, CacheWriteBuffer* buf,
const uint64_t file_off,
const std::function<void()> callback) = 0;
// stop the writer
virtual void Stop() = 0;
PersistentCacheTier* const cache_;
};
// class BlockCacheFile
//
// Generic interface to support building file specialized for read/writing
class BlockCacheFile : public LRUElement<BlockCacheFile> {
public:
explicit BlockCacheFile(const uint32_t cache_id)
: LRUElement<BlockCacheFile>(), cache_id_(cache_id) {}
explicit BlockCacheFile(Env* const env, const std::string& dir,
const uint32_t cache_id)
: LRUElement<BlockCacheFile>(),
env_(env),
dir_(dir),
cache_id_(cache_id) {}
virtual ~BlockCacheFile() {}
// append key/value to file and return LBA locator to user
virtual bool Append(const Slice& key, const Slice& val, LBA* const lba) {
assert(!"not implemented");
return false;
}
// read from the record locator (LBA) and return key, value and status
virtual bool Read(const LBA& lba, Slice* key, Slice* block, char* scratch) {
assert(!"not implemented");
return false;
}
// get file path
std::string Path() const {
return dir_ + "/" + std::to_string(cache_id_) + ".rc";
}
// get cache ID
uint32_t cacheid() const { return cache_id_; }
// Add block information to file data
// Block information is the list of index reference for this file
virtual void Add(BlockInfo* binfo) {
WriteLock _(&rwlock_);
block_infos_.push_back(binfo);
}
// get block information
std::list<BlockInfo*>& block_infos() { return block_infos_; }
// delete file and return the size of the file
virtual Status Delete(uint64_t* size);
protected:
port::RWMutex rwlock_; // synchronization mutex
Env* const env_ = nullptr; // Env for IO
const std::string dir_; // Directory name
const uint32_t cache_id_; // Cache id for the file
std::list<BlockInfo*> block_infos_; // List of index entries mapping to the
// file content
};
// class RandomAccessFile
//
// Thread safe implementation for reading random data from file
class RandomAccessCacheFile : public BlockCacheFile {
public:
explicit RandomAccessCacheFile(Env* const env, const std::string& dir,
const uint32_t cache_id,
const shared_ptr<Logger>& log)
: BlockCacheFile(env, dir, cache_id), log_(log) {}
virtual ~RandomAccessCacheFile() {}
// open file for reading
bool Open(const bool enable_direct_reads);
// read data from the disk
bool Read(const LBA& lba, Slice* key, Slice* block, char* scratch) override;
private:
std::unique_ptr<RandomAccessFileReader> freader_;
protected:
bool OpenImpl(const bool enable_direct_reads);
bool ParseRec(const LBA& lba, Slice* key, Slice* val, char* scratch);
std::shared_ptr<Logger> log_; // log file
};
// class WriteableCacheFile
//
// All writes to the files are cached in buffers. The buffers are flushed to
// disk as they get filled up. When file size reaches a certain size, a new file
// will be created provided there is free space
class WriteableCacheFile : public RandomAccessCacheFile {
public:
explicit WriteableCacheFile(Env* const env, CacheWriteBufferAllocator* alloc,
Writer* writer, const std::string& dir,
const uint32_t cache_id, const uint32_t max_size,
const std::shared_ptr<Logger>& log)
: RandomAccessCacheFile(env, dir, cache_id, log),
alloc_(alloc),
writer_(writer),
max_size_(max_size) {}
virtual ~WriteableCacheFile();
// create file on disk
bool Create(const bool enable_direct_writes, const bool enable_direct_reads);
// read data from logical file
bool Read(const LBA& lba, Slice* key, Slice* block, char* scratch) override {
ReadLock _(&rwlock_);
const bool closed = eof_ && bufs_.empty();
if (closed) {
// the file is closed, read from disk
return RandomAccessCacheFile::Read(lba, key, block, scratch);
}
// file is still being written, read from buffers
return ReadBuffer(lba, key, block, scratch);
}
// append data to end of file
bool Append(const Slice&, const Slice&, LBA* const) override;
// End-of-file
bool Eof() const { return eof_; }
private:
friend class ThreadedWriter;
static const size_t kFileAlignmentSize = 4 * 1024; // align file size
bool ReadBuffer(const LBA& lba, Slice* key, Slice* block, char* scratch);
bool ReadBuffer(const LBA& lba, char* data);
bool ExpandBuffer(const size_t size);
void DispatchBuffer();
void BufferWriteDone();
void CloseAndOpenForReading();
void ClearBuffers();
void Close();
// File layout in memory
//
// +------+------+------+------+------+------+
// | b0 | b1 | b2 | b3 | b4 | b5 |
// +------+------+------+------+------+------+
// ^ ^
// | |
// buf_doff_ buf_woff_
// (next buffer to (next buffer to fill)
// flush to disk)
//
// The buffers are flushed to disk serially for a given file
CacheWriteBufferAllocator* const alloc_ = nullptr; // Buffer provider
Writer* const writer_ = nullptr; // File writer thread
std::unique_ptr<WritableFile> file_; // RocksDB Env file abstraction
std::vector<CacheWriteBuffer*> bufs_; // Written buffers
uint32_t size_ = 0; // Size of the file
const uint32_t max_size_; // Max size of the file
bool eof_ = false; // End of file
uint32_t disk_woff_ = 0; // Offset to write on disk
size_t buf_woff_ = 0; // off into bufs_ to write
size_t buf_doff_ = 0; // off into bufs_ to dispatch
size_t pending_ios_ = 0; // Number of ios to disk in-progress
bool enable_direct_reads_ = false; // Should we enable direct reads
// when reading from disk
};
//
// Abstraction to do writing to device. It is part of pipelined architecture.
//
class ThreadedWriter : public Writer {
public:
// Representation of IO to device
struct IO {
explicit IO(const bool signal) : signal_(signal) {}
explicit IO(WritableFile* const file, CacheWriteBuffer* const buf,
const uint64_t file_off, const std::function<void()> callback)
: file_(file), buf_(buf), file_off_(file_off), callback_(callback) {}
IO(const IO&) = default;
IO& operator=(const IO&) = default;
size_t Size() const { return sizeof(IO); }
WritableFile* file_ = nullptr; // File to write to
CacheWriteBuffer* const buf_ = nullptr; // buffer to write
uint64_t file_off_ = 0; // file offset
bool signal_ = false; // signal to exit thread loop
std::function<void()> callback_; // Callback on completion
};
explicit ThreadedWriter(PersistentCacheTier* const cache, const size_t qdepth,
const size_t io_size);
virtual ~ThreadedWriter() { assert(threads_.empty()); }
void Stop() override;
void Write(WritableFile* const file, CacheWriteBuffer* buf,
const uint64_t file_off,
const std::function<void()> callback) override;
private:
void ThreadMain();
void DispatchIO(const IO& io);
const size_t io_size_ = 0;
BoundedQueue<IO> q_;
std::vector<port::Thread> threads_;
};
} // namespace rocksdb
#endif