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rocksdb/db/blob/blob_file_reader.cc

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Introduce a blob file reader class (#7461) Summary: The patch adds a class called `BlobFileReader` that can be used to retrieve blobs using the information available in blob references (e.g. blob file number, offset, and size). This will come in handy when implementing blob support for `Get`, `MultiGet`, and iterators, and also for compaction/garbage collection. When a `BlobFileReader` object is created (using the factory method `Create`), it first checks whether the specified file is potentially valid by comparing the file size against the combined size of the blob file header and footer (files smaller than the threshold are considered malformed). Then, it opens the file, and reads and verifies the header and footer. The verification involves magic number/CRC checks as well as checking for unexpected header/footer fields, e.g. incorrect column family ID or TTL blob files. Blobs can be retrieved using `GetBlob`. `GetBlob` validates the offset and compression type passed by the caller (because of the presence of the header and footer, the specified offset cannot be too close to the start/end of the file; also, the compression type has to match the one in the blob file header), and retrieves and potentially verifies and uncompresses the blob. In particular, when `ReadOptions::verify_checksums` is set, `BlobFileReader` reads the blob record header as well (as opposed to just the blob itself) and verifies the key/value size, the key itself, as well as the CRC of the blob record header and the key/value pair. In addition, the patch exposes the compression type from `BlobIndex` (both using an accessor and via `DebugString`), and adds a blob file read latency histogram to `InternalStats` that can be used with `BlobFileReader`. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7461 Test Plan: `make check` Reviewed By: riversand963 Differential Revision: D23999219 Pulled By: ltamasi fbshipit-source-id: deb6b1160d251258b308d5156e2ec063c3e12e5e
4 years ago
// Copyright (c) 2011-present, 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).
#include "db/blob/blob_file_reader.h"
#include <cassert>
#include <string>
#include "db/blob/blob_log_format.h"
#include "file/filename.h"
#include "options/cf_options.h"
#include "rocksdb/file_system.h"
#include "rocksdb/slice.h"
#include "rocksdb/status.h"
#include "test_util/sync_point.h"
#include "util/compression.h"
#include "util/crc32c.h"
namespace ROCKSDB_NAMESPACE {
Status BlobFileReader::Create(
const ImmutableCFOptions& immutable_cf_options,
const FileOptions& file_options, uint32_t column_family_id,
HistogramImpl* blob_file_read_hist, uint64_t blob_file_number,
std::unique_ptr<BlobFileReader>* blob_file_reader) {
assert(blob_file_reader);
assert(!*blob_file_reader);
uint64_t file_size = 0;
std::unique_ptr<RandomAccessFileReader> file_reader;
{
const Status s =
OpenFile(immutable_cf_options, file_options, blob_file_read_hist,
blob_file_number, &file_size, &file_reader);
if (!s.ok()) {
return s;
}
}
assert(file_reader);
CompressionType compression_type = kNoCompression;
{
const Status s =
ReadHeader(file_reader.get(), column_family_id, &compression_type);
if (!s.ok()) {
return s;
}
}
{
const Status s = ReadFooter(file_size, file_reader.get());
if (!s.ok()) {
return s;
}
}
blob_file_reader->reset(
new BlobFileReader(std::move(file_reader), file_size, compression_type));
return Status::OK();
}
Status BlobFileReader::OpenFile(
const ImmutableCFOptions& immutable_cf_options,
const FileOptions& file_opts, HistogramImpl* blob_file_read_hist,
uint64_t blob_file_number, uint64_t* file_size,
std::unique_ptr<RandomAccessFileReader>* file_reader) {
assert(file_size);
assert(file_reader);
const auto& cf_paths = immutable_cf_options.cf_paths;
assert(!cf_paths.empty());
const std::string blob_file_path =
BlobFileName(cf_paths.front().path, blob_file_number);
FileSystem* const fs = immutable_cf_options.fs;
assert(fs);
constexpr IODebugContext* dbg = nullptr;
{
TEST_SYNC_POINT("BlobFileReader::OpenFile:GetFileSize");
const Status s =
fs->GetFileSize(blob_file_path, IOOptions(), file_size, dbg);
if (!s.ok()) {
return s;
}
}
if (*file_size < BlobLogHeader::kSize + BlobLogFooter::kSize) {
return Status::Corruption("Malformed blob file");
}
std::unique_ptr<FSRandomAccessFile> file;
{
TEST_SYNC_POINT("BlobFileReader::OpenFile:NewRandomAccessFile");
const Status s =
fs->NewRandomAccessFile(blob_file_path, file_opts, &file, dbg);
if (!s.ok()) {
return s;
}
}
assert(file);
if (immutable_cf_options.advise_random_on_open) {
file->Hint(FSRandomAccessFile::kRandom);
}
file_reader->reset(new RandomAccessFileReader(
std::move(file), blob_file_path, immutable_cf_options.env,
std::shared_ptr<IOTracer>(), immutable_cf_options.statistics,
BLOB_DB_BLOB_FILE_READ_MICROS, blob_file_read_hist,
immutable_cf_options.rate_limiter, immutable_cf_options.listeners));
return Status::OK();
}
Status BlobFileReader::ReadHeader(const RandomAccessFileReader* file_reader,
uint32_t column_family_id,
CompressionType* compression_type) {
assert(file_reader);
assert(compression_type);
Slice header_slice;
Buffer buf;
AlignedBuf aligned_buf;
{
TEST_SYNC_POINT("BlobFileReader::ReadHeader:ReadFromFile");
constexpr uint64_t read_offset = 0;
constexpr size_t read_size = BlobLogHeader::kSize;
const Status s = ReadFromFile(file_reader, read_offset, read_size,
&header_slice, &buf, &aligned_buf);
if (!s.ok()) {
return s;
}
TEST_SYNC_POINT_CALLBACK("BlobFileReader::ReadHeader:TamperWithResult",
&header_slice);
}
BlobLogHeader header;
{
const Status s = header.DecodeFrom(header_slice);
if (!s.ok()) {
return s;
}
}
constexpr ExpirationRange no_expiration_range;
if (header.has_ttl || header.expiration_range != no_expiration_range) {
return Status::Corruption("Unexpected TTL blob file");
}
if (header.column_family_id != column_family_id) {
return Status::Corruption("Column family ID mismatch");
}
*compression_type = header.compression;
return Status::OK();
}
Status BlobFileReader::ReadFooter(uint64_t file_size,
const RandomAccessFileReader* file_reader) {
assert(file_size >= BlobLogHeader::kSize + BlobLogFooter::kSize);
assert(file_reader);
Slice footer_slice;
Buffer buf;
AlignedBuf aligned_buf;
{
TEST_SYNC_POINT("BlobFileReader::ReadFooter:ReadFromFile");
const uint64_t read_offset = file_size - BlobLogFooter::kSize;
constexpr size_t read_size = BlobLogFooter::kSize;
const Status s = ReadFromFile(file_reader, read_offset, read_size,
&footer_slice, &buf, &aligned_buf);
if (!s.ok()) {
return s;
}
TEST_SYNC_POINT_CALLBACK("BlobFileReader::ReadFooter:TamperWithResult",
&footer_slice);
}
BlobLogFooter footer;
{
const Status s = footer.DecodeFrom(footer_slice);
if (!s.ok()) {
return s;
}
}
constexpr ExpirationRange no_expiration_range;
if (footer.expiration_range != no_expiration_range) {
return Status::Corruption("Unexpected TTL blob file");
}
return Status::OK();
}
Status BlobFileReader::ReadFromFile(const RandomAccessFileReader* file_reader,
uint64_t read_offset, size_t read_size,
Slice* slice, Buffer* buf,
AlignedBuf* aligned_buf) {
assert(slice);
assert(buf);
assert(aligned_buf);
assert(file_reader);
Status s;
if (file_reader->use_direct_io()) {
constexpr char* scratch = nullptr;
s = file_reader->Read(IOOptions(), read_offset, read_size, slice, scratch,
aligned_buf);
} else {
buf->reset(new char[read_size]);
constexpr AlignedBuf* aligned_scratch = nullptr;
s = file_reader->Read(IOOptions(), read_offset, read_size, slice,
buf->get(), aligned_scratch);
}
if (!s.ok()) {
return s;
}
if (slice->size() != read_size) {
return Status::Corruption("Failed to read data from blob file");
}
return Status::OK();
}
BlobFileReader::BlobFileReader(
std::unique_ptr<RandomAccessFileReader>&& file_reader, uint64_t file_size,
CompressionType compression_type)
: file_reader_(std::move(file_reader)),
file_size_(file_size),
compression_type_(compression_type) {
assert(file_reader_);
}
BlobFileReader::~BlobFileReader() = default;
Status BlobFileReader::GetBlob(const ReadOptions& read_options,
const Slice& user_key, uint64_t offset,
uint64_t value_size,
CompressionType compression_type,
PinnableSlice* value) const {
assert(value);
const uint64_t key_size = user_key.size();
if (!IsValidBlobOffset(offset, key_size, value_size, file_size_)) {
return Status::Corruption("Invalid blob offset");
}
if (compression_type != compression_type_) {
return Status::Corruption("Compression type mismatch when reading blob");
}
// Note: if verify_checksum is set, we read the entire blob record to be able
// to perform the verification; otherwise, we just read the blob itself. Since
// the offset in BlobIndex actually points to the blob value, we need to make
// an adjustment in the former case.
const uint64_t adjustment =
read_options.verify_checksums
? BlobLogRecord::CalculateAdjustmentForRecordHeader(key_size)
: 0;
assert(offset >= adjustment);
Slice record_slice;
Buffer buf;
AlignedBuf aligned_buf;
{
TEST_SYNC_POINT("BlobFileReader::GetBlob:ReadFromFile");
const uint64_t record_offset = offset - adjustment;
const uint64_t record_size = value_size + adjustment;
const Status s = ReadFromFile(file_reader_.get(), record_offset,
static_cast<size_t>(record_size),
&record_slice, &buf, &aligned_buf);
if (!s.ok()) {
return s;
}
TEST_SYNC_POINT_CALLBACK("BlobFileReader::GetBlob:TamperWithResult",
&record_slice);
}
if (read_options.verify_checksums) {
const Status s = VerifyBlob(record_slice, user_key, value_size);
if (!s.ok()) {
return s;
}
}
const Slice value_slice(record_slice.data() + adjustment, value_size);
{
const Status s =
UncompressBlobIfNeeded(value_slice, compression_type, value);
if (!s.ok()) {
return s;
}
}
return Status::OK();
}
Status BlobFileReader::VerifyBlob(const Slice& record_slice,
const Slice& user_key, uint64_t value_size) {
BlobLogRecord record;
const Slice header_slice(record_slice.data(), BlobLogRecord::kHeaderSize);
{
const Status s = record.DecodeHeaderFrom(header_slice);
if (!s.ok()) {
return s;
}
}
if (record.key_size != user_key.size()) {
return Status::Corruption("Key size mismatch when reading blob");
}
if (record.value_size != value_size) {
return Status::Corruption("Value size mismatch when reading blob");
}
record.key =
Slice(record_slice.data() + BlobLogRecord::kHeaderSize, record.key_size);
if (record.key != user_key) {
return Status::Corruption("Key mismatch when reading blob");
}
record.value = Slice(record.key.data() + record.key_size, value_size);
{
TEST_SYNC_POINT_CALLBACK("BlobFileReader::VerifyBlob:CheckBlobCRC",
&record);
const Status s = record.CheckBlobCRC();
if (!s.ok()) {
return s;
}
}
return Status::OK();
}
Status BlobFileReader::UncompressBlobIfNeeded(const Slice& value_slice,
CompressionType compression_type,
PinnableSlice* value) {
assert(value);
if (compression_type == kNoCompression) {
SaveValue(value_slice, value);
return Status::OK();
}
UncompressionContext context(compression_type);
UncompressionInfo info(context, UncompressionDict::GetEmptyDict(),
compression_type);
size_t uncompressed_size = 0;
constexpr uint32_t compression_format_version = 2;
constexpr MemoryAllocator* allocator = nullptr;
CacheAllocationPtr output =
UncompressData(info, value_slice.data(), value_slice.size(),
&uncompressed_size, compression_format_version, allocator);
TEST_SYNC_POINT_CALLBACK(
"BlobFileReader::UncompressBlobIfNeeded:TamperWithResult", &output);
if (!output) {
return Status::Corruption("Unable to uncompress blob");
}
SaveValue(Slice(output.get(), uncompressed_size), value);
return Status::OK();
}
void BlobFileReader::SaveValue(const Slice& src, PinnableSlice* dst) {
assert(dst);
if (dst->IsPinned()) {
dst->Reset();
}
dst->PinSelf(src);
}
} // namespace ROCKSDB_NAMESPACE