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rocksdb/db/blob/blob_source.cc

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// Copyright (c) Meta Platforms, Inc. and affiliates.
// 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).
#include "db/blob/blob_source.h"
#include <cassert>
#include <string>
#include "db/blob/blob_file_reader.h"
#include "options/cf_options.h"
namespace ROCKSDB_NAMESPACE {
BlobSource::BlobSource(const ImmutableOptions* immutable_options,
const std::string& db_id,
const std::string& db_session_id,
BlobFileCache* blob_file_cache)
: db_id_(db_id),
db_session_id_(db_session_id),
statistics_(immutable_options->statistics.get()),
blob_file_cache_(blob_file_cache),
blob_cache_(immutable_options->blob_cache) {}
BlobSource::~BlobSource() = default;
Status BlobSource::GetBlobFromCache(const Slice& cache_key,
CachableEntry<std::string>* blob) const {
assert(blob);
assert(blob->IsEmpty());
assert(blob_cache_);
assert(!cache_key.empty());
Cache::Handle* cache_handle = nullptr;
cache_handle = GetEntryFromCache(cache_key);
if (cache_handle != nullptr) {
blob->SetCachedValue(
static_cast<std::string*>(blob_cache_->Value(cache_handle)),
blob_cache_.get(), cache_handle);
return Status::OK();
}
assert(blob->IsEmpty());
return Status::NotFound("Blob not found in cache");
}
Status BlobSource::PutBlobIntoCache(const Slice& cache_key,
CachableEntry<std::string>* cached_blob,
PinnableSlice* blob) const {
assert(blob);
assert(!cache_key.empty());
assert(blob_cache_);
Status s;
const Cache::Priority priority = Cache::Priority::LOW;
// Objects to be put into the cache have to be heap-allocated and
// self-contained, i.e. own their contents. The Cache has to be able to take
// unique ownership of them. Therefore, we copy the blob into a string
// directly, and insert that into the cache.
std::string* buf = new std::string();
buf->assign(blob->data(), blob->size());
// TODO: support custom allocators and provide a better estimated memory
// usage using malloc_usable_size.
Cache::Handle* cache_handle = nullptr;
s = InsertEntryIntoCache(cache_key, buf, buf->size(), &cache_handle,
priority);
if (s.ok()) {
assert(cache_handle != nullptr);
cached_blob->SetCachedValue(buf, blob_cache_.get(), cache_handle);
}
return s;
}
Status BlobSource::GetBlob(const ReadOptions& read_options,
const Slice& user_key, uint64_t file_number,
uint64_t offset, uint64_t file_size,
uint64_t value_size,
CompressionType compression_type,
FilePrefetchBuffer* prefetch_buffer,
PinnableSlice* value, uint64_t* bytes_read) {
assert(value);
Status s;
const CacheKey cache_key = GetCacheKey(file_number, file_size, offset);
CachableEntry<std::string> blob_entry;
// First, try to get the blob from the cache
//
// If blob cache is enabled, we'll try to read from it.
if (blob_cache_) {
Slice key = cache_key.AsSlice();
s = GetBlobFromCache(key, &blob_entry);
if (s.ok() && blob_entry.GetValue()) {
assert(blob_entry.GetValue()->size() == value_size);
if (bytes_read) {
*bytes_read = value_size;
}
value->PinSelf(*blob_entry.GetValue());
return s;
}
}
assert(blob_entry.IsEmpty());
const bool no_io = read_options.read_tier == kBlockCacheTier;
if (no_io) {
return Status::Incomplete("Cannot read blob(s): no disk I/O allowed");
}
// Can't find the blob from the cache. Since I/O is allowed, read from the
// file.
{
CacheHandleGuard<BlobFileReader> blob_file_reader;
s = blob_file_cache_->GetBlobFileReader(file_number, &blob_file_reader);
if (!s.ok()) {
return s;
}
assert(blob_file_reader.GetValue());
if (compression_type != blob_file_reader.GetValue()->GetCompressionType()) {
return Status::Corruption("Compression type mismatch when reading blob");
}
s = blob_file_reader.GetValue()->GetBlob(
read_options, user_key, offset, value_size, compression_type,
prefetch_buffer, value, bytes_read);
if (!s.ok()) {
return s;
}
}
if (blob_cache_ && read_options.fill_cache) {
// If filling cache is allowed and a cache is configured, try to put the
// blob to the cache.
Slice key = cache_key.AsSlice();
s = PutBlobIntoCache(key, &blob_entry, value);
if (!s.ok()) {
return s;
}
}
assert(s.ok());
return s;
}
bool BlobSource::TEST_BlobInCache(uint64_t file_number, uint64_t file_size,
uint64_t offset) const {
const CacheKey cache_key = GetCacheKey(file_number, file_size, offset);
const Slice key = cache_key.AsSlice();
CachableEntry<std::string> blob_entry;
const Status s = GetBlobFromCache(key, &blob_entry);
if (s.ok() && blob_entry.GetValue() != nullptr) {
return true;
}
return false;
}
} // namespace ROCKSDB_NAMESPACE