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c965c9ef65
Summary: There is currently no caching mechanism for blobs, which is not ideal especially when the database resides on remote storage (where we cannot rely on the OS page cache). As part of this task, we would like to make it possible for the application to configure a blob cache. In this task, we added a new abstraction layer `BlobSource` to retrieve blobs from either blob cache or raw blob file. Note: For simplicity, the current PR only includes `GetBlob()`. `MultiGetBlob()` will be included in the next PR. This PR is a part of https://github.com/facebook/rocksdb/issues/10156 Pull Request resolved: https://github.com/facebook/rocksdb/pull/10178 Reviewed By: ltamasi Differential Revision: D37250507 Pulled By: gangliao fbshipit-source-id: 3fc4a55a0cea955a3147bdc7dba06430e377259b
89 lines
3 KiB
C++
89 lines
3 KiB
C++
// Copyright (c) Meta Platforms, Inc. and affiliates.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <cinttypes>
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#include "cache/cache_helpers.h"
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#include "cache/cache_key.h"
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#include "db/blob/blob_file_cache.h"
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#include "include/rocksdb/cache.h"
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#include "rocksdb/rocksdb_namespace.h"
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#include "table/block_based/cachable_entry.h"
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namespace ROCKSDB_NAMESPACE {
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struct ImmutableOptions;
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class Status;
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class FilePrefetchBuffer;
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class Slice;
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// BlobSource is a class that provides universal access to blobs, regardless of
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// whether they are in the blob cache, secondary cache, or (remote) storage.
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// Depending on user settings, it always fetch blobs from multi-tier cache and
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// storage with minimal cost.
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class BlobSource {
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public:
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BlobSource(const ImmutableOptions* immutable_options,
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const std::string& db_id, const std::string& db_session_id,
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BlobFileCache* blob_file_cache);
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BlobSource(const BlobSource&) = delete;
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BlobSource& operator=(const BlobSource&) = delete;
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~BlobSource();
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Status GetBlob(const ReadOptions& read_options, const Slice& user_key,
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uint64_t file_number, uint64_t offset, uint64_t file_size,
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uint64_t value_size, CompressionType compression_type,
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FilePrefetchBuffer* prefetch_buffer, PinnableSlice* value,
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uint64_t* bytes_read);
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bool TEST_BlobInCache(uint64_t file_number, uint64_t file_size,
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uint64_t offset) const;
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private:
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Status GetBlobFromCache(const Slice& cache_key,
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CachableEntry<std::string>* blob) const;
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Status PutBlobIntoCache(const Slice& cache_key,
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CachableEntry<std::string>* cached_blob,
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PinnableSlice* blob) const;
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inline CacheKey GetCacheKey(uint64_t file_number, uint64_t file_size,
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uint64_t offset) const {
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OffsetableCacheKey base_cache_key(db_id_, db_session_id_, file_number,
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file_size);
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return base_cache_key.WithOffset(offset);
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}
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inline Cache::Handle* GetEntryFromCache(const Slice& key) const {
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return blob_cache_->Lookup(key, statistics_);
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}
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inline Status InsertEntryIntoCache(const Slice& key, std::string* value,
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size_t charge,
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Cache::Handle** cache_handle,
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Cache::Priority priority) const {
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return blob_cache_->Insert(key, value, charge,
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&DeleteCacheEntry<std::string>, cache_handle,
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priority);
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}
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const std::string db_id_;
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const std::string db_session_id_;
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Statistics* statistics_;
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// A cache to store blob file reader.
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BlobFileCache* blob_file_cache_;
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// A cache to store uncompressed blobs.
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std::shared_ptr<Cache> blob_cache_;
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};
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} // namespace ROCKSDB_NAMESPACE
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