//  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 "cache/cache_reservation_manager.h"

#include "cache/charged_cache.h"

#include "db/blob/blob_contents.h"

#include "db/blob/blob_file_reader.h"

#include "db/blob/blob_log_format.h"

#include "monitoring/statistics_impl.h"

#include "options/cf_options.h"

#include "table/get_context.h"

#include "table/multiget_context.h"

namespace ROCKSDB_NAMESPACE {

BlobSource::BlobSource(const ImmutableOptions& immutable_options,

                       const MutableCFOptions& mutable_cf_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),

      lowest_used_cache_tier_(immutable_options.lowest_used_cache_tier) {

  auto bbto =

      mutable_cf_options.table_factory->GetOptions<BlockBasedTableOptions>();

  if (bbto &&

      bbto->cache_usage_options.options_overrides.at(CacheEntryRole::kBlobCache)

              .charged == CacheEntryRoleOptions::Decision::kEnabled) {

    blob_cache_ = SharedCacheInterface{std::make_shared<ChargedCache>(

        immutable_options.blob_cache, bbto->block_cache)};

  }

}

BlobSource::~BlobSource() = default;

Status BlobSource::GetBlobFromCache(

    const Slice& cache_key, CacheHandleGuard<BlobContents>* cached_blob) const {

  assert(blob_cache_);

  assert(!cache_key.empty());

  assert(cached_blob);

  assert(cached_blob->IsEmpty());

  Cache::Handle* cache_handle = nullptr;

  cache_handle = GetEntryFromCache(cache_key);

  if (cache_handle != nullptr) {

    *cached_blob =

        CacheHandleGuard<BlobContents>(blob_cache_.get(), cache_handle);

    assert(cached_blob->GetValue());

    PERF_COUNTER_ADD(blob_cache_hit_count, 1);

    RecordTick(statistics_, BLOB_DB_CACHE_HIT);

    RecordTick(statistics_, BLOB_DB_CACHE_BYTES_READ,

               cached_blob->GetValue()->size());

    return Status::OK();

  }

  RecordTick(statistics_, BLOB_DB_CACHE_MISS);

  return Status::NotFound("Blob not found in cache");

}

Status BlobSource::PutBlobIntoCache(

    const Slice& cache_key, std::unique_ptr<BlobContents>* blob,

    CacheHandleGuard<BlobContents>* cached_blob) const {

  assert(blob_cache_);

  assert(!cache_key.empty());

  assert(blob);

  assert(*blob);

  assert(cached_blob);

  assert(cached_blob->IsEmpty());

  TypedHandle* cache_handle = nullptr;

  const Status s = InsertEntryIntoCache(cache_key, blob->get(), &cache_handle,

                                        Cache::Priority::BOTTOM);

  if (s.ok()) {

    blob->release();

    assert(cache_handle != nullptr);

    *cached_blob =

        CacheHandleGuard<BlobContents>(blob_cache_.get(), cache_handle);

    assert(cached_blob->GetValue());

    RecordTick(statistics_, BLOB_DB_CACHE_ADD);

    RecordTick(statistics_, BLOB_DB_CACHE_BYTES_WRITE,

               cached_blob->GetValue()->size());

  } else {

    RecordTick(statistics_, BLOB_DB_CACHE_ADD_FAILURES);

  }

  return s;

}

BlobSource::TypedHandle* BlobSource::GetEntryFromCache(const Slice& key) const {

  return blob_cache_.LookupFull(key, nullptr /* context */,

                                Cache::Priority::BOTTOM, statistics_,

                                lowest_used_cache_tier_);

}

void BlobSource::PinCachedBlob(CacheHandleGuard<BlobContents>* cached_blob,

                               PinnableSlice* value) {

  assert(cached_blob);

  assert(cached_blob->GetValue());

  assert(value);

  // To avoid copying the cached blob into the buffer provided by the

  // application, we can simply transfer ownership of the cache handle to

  // the target PinnableSlice. This has the potential to save a lot of

  // CPU, especially with large blob values.

  value->Reset();

  constexpr Cleanable* cleanable = nullptr;

  value->PinSlice(cached_blob->GetValue()->data(), cleanable);

  cached_blob->TransferTo(value);

}

void BlobSource::PinOwnedBlob(std::unique_ptr<BlobContents>* owned_blob,

                              PinnableSlice* value) {

  assert(owned_blob);

  assert(*owned_blob);

  assert(value);

  BlobContents* const blob = owned_blob->release();

  assert(blob);

  value->Reset();

  value->PinSlice(

      blob->data(),

      [](void* arg1, void* /* arg2 */) {

        delete static_cast<BlobContents*>(arg1);

      },

      blob, nullptr);

}

Status BlobSource::InsertEntryIntoCache(const Slice& key, BlobContents* value,

                                        TypedHandle** cache_handle,

                                        Cache::Priority priority) const {

  return blob_cache_.InsertFull(key, value, value->ApproximateMemoryUsage(),

                                cache_handle, priority,

                                lowest_used_cache_tier_);

}

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);

  CacheHandleGuard<BlobContents> blob_handle;

  // 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_handle);

    if (s.ok()) {

      PinCachedBlob(&blob_handle, value);

      // For consistency, the size of on-disk (possibly compressed) blob record

      // is assigned to bytes_read.

      uint64_t adjustment =

          read_options.verify_checksums

              ? BlobLogRecord::CalculateAdjustmentForRecordHeader(

                    user_key.size())

              : 0;

      assert(offset >= adjustment);

      uint64_t record_size = value_size + adjustment;

      if (bytes_read) {

        *bytes_read = record_size;

      }

      return s;

    }

  }

  assert(blob_handle.IsEmpty());

  const bool no_io = read_options.read_tier == kBlockCacheTier;

  if (no_io) {

    s = Status::Incomplete("Cannot read blob(s): no disk I/O allowed");

    return s;

  }

  // Can't find the blob from the cache. Since I/O is allowed, read from the

  // file.

  std::unique_ptr<BlobContents> blob_contents;

  {

    CacheHandleGuard<BlobFileReader> blob_file_reader;

    s = blob_file_cache_->GetBlobFileReader(read_options, 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");

    }

    MemoryAllocator* const allocator =

        (blob_cache_ && read_options.fill_cache)

            ? blob_cache_.get()->memory_allocator()

            : nullptr;

    uint64_t read_size = 0;

    s = blob_file_reader.GetValue()->GetBlob(

        read_options, user_key, offset, value_size, compression_type,

        prefetch_buffer, allocator, &blob_contents, &read_size);

    if (!s.ok()) {

      return s;

    }

    if (bytes_read) {

      *bytes_read = read_size;

    }

  }

  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_contents, &blob_handle);

    if (!s.ok()) {

      return s;

    }

    PinCachedBlob(&blob_handle, value);

  } else {

    PinOwnedBlob(&blob_contents, value);

  }

  assert(s.ok());

  return s;

}

void BlobSource::MultiGetBlob(const ReadOptions& read_options,

                              autovector<BlobFileReadRequests>& blob_reqs,

                              uint64_t* bytes_read) {

  assert(blob_reqs.size() > 0);

  uint64_t total_bytes_read = 0;

  uint64_t bytes_read_in_file = 0;

  for (auto& [file_number, file_size, blob_reqs_in_file] : blob_reqs) {

    // sort blob_reqs_in_file by file offset.

    std::sort(

        blob_reqs_in_file.begin(), blob_reqs_in_file.end(),

        [](const BlobReadRequest& lhs, const BlobReadRequest& rhs) -> bool {

          return lhs.offset < rhs.offset;

        });

    MultiGetBlobFromOneFile(read_options, file_number, file_size,

                            blob_reqs_in_file, &bytes_read_in_file);

    total_bytes_read += bytes_read_in_file;

  }

  if (bytes_read) {

    *bytes_read = total_bytes_read;

  }

}

void BlobSource::MultiGetBlobFromOneFile(const ReadOptions& read_options,

                                         uint64_t file_number,

                                         uint64_t /*file_size*/,

                                         autovector<BlobReadRequest>& blob_reqs,

                                         uint64_t* bytes_read) {

  const size_t num_blobs = blob_reqs.size();

  assert(num_blobs > 0);

  assert(num_blobs <= MultiGetContext::MAX_BATCH_SIZE);

#ifndef NDEBUG

  for (size_t i = 0; i < num_blobs - 1; ++i) {

    assert(blob_reqs[i].offset <= blob_reqs[i + 1].offset);

  }

#endif  // !NDEBUG

  using Mask = uint64_t;

  Mask cache_hit_mask = 0;

  uint64_t total_bytes = 0;

  const OffsetableCacheKey base_cache_key(db_id_, db_session_id_, file_number);

  if (blob_cache_) {

    size_t cached_blob_count = 0;

    for (size_t i = 0; i < num_blobs; ++i) {

      auto& req = blob_reqs[i];

      CacheHandleGuard<BlobContents> blob_handle;

      const CacheKey cache_key = base_cache_key.WithOffset(req.offset);

      const Slice key = cache_key.AsSlice();

      const Status s = GetBlobFromCache(key, &blob_handle);

      if (s.ok()) {

        assert(req.status);

        *req.status = s;

        PinCachedBlob(&blob_handle, req.result);

        // Update the counter for the number of valid blobs read from the cache.

        ++cached_blob_count;

        // For consistency, the size of each on-disk (possibly compressed) blob

        // record is accumulated to total_bytes.

        uint64_t adjustment =

            read_options.verify_checksums

                ? BlobLogRecord::CalculateAdjustmentForRecordHeader(

                      req.user_key->size())

                : 0;

        assert(req.offset >= adjustment);

        total_bytes += req.len + adjustment;

        cache_hit_mask |= (Mask{1} << i);  // cache hit

      }

    }

    // All blobs were read from the cache.

    if (cached_blob_count == num_blobs) {

      if (bytes_read) {

        *bytes_read = total_bytes;

      }

      return;

    }

  }

  const bool no_io = read_options.read_tier == kBlockCacheTier;

  if (no_io) {

    for (size_t i = 0; i < num_blobs; ++i) {

      if (!(cache_hit_mask & (Mask{1} << i))) {

        BlobReadRequest& req = blob_reqs[i];

        assert(req.status);

        *req.status =

            Status::Incomplete("Cannot read blob(s): no disk I/O allowed");

      }

    }

    return;

  }

  {

    // Find the rest of blobs from the file since I/O is allowed.

    autovector<std::pair<BlobReadRequest*, std::unique_ptr<BlobContents>>>

        _blob_reqs;

    uint64_t _bytes_read = 0;

    for (size_t i = 0; i < num_blobs; ++i) {

      if (!(cache_hit_mask & (Mask{1} << i))) {

        _blob_reqs.emplace_back(&blob_reqs[i], std::unique_ptr<BlobContents>());

      }

    }

    CacheHandleGuard<BlobFileReader> blob_file_reader;

    Status s = blob_file_cache_->GetBlobFileReader(read_options, file_number,

                                                   &blob_file_reader);

    if (!s.ok()) {

      for (size_t i = 0; i < _blob_reqs.size(); ++i) {

        BlobReadRequest* const req = _blob_reqs[i].first;

        assert(req);

        assert(req->status);

        *req->status = s;

      }

      return;

    }

    assert(blob_file_reader.GetValue());

    MemoryAllocator* const allocator =

        (blob_cache_ && read_options.fill_cache)

            ? blob_cache_.get()->memory_allocator()

            : nullptr;

    blob_file_reader.GetValue()->MultiGetBlob(read_options, allocator,

                                              _blob_reqs, &_bytes_read);

    if (blob_cache_ && read_options.fill_cache) {

      // If filling cache is allowed and a cache is configured, try to put

      // the blob(s) to the cache.

      for (auto& [req, blob_contents] : _blob_reqs) {

        assert(req);

        if (req->status->ok()) {

          CacheHandleGuard<BlobContents> blob_handle;

          const CacheKey cache_key = base_cache_key.WithOffset(req->offset);

          const Slice key = cache_key.AsSlice();

          s = PutBlobIntoCache(key, &blob_contents, &blob_handle);

          if (!s.ok()) {

            *req->status = s;

          } else {

            PinCachedBlob(&blob_handle, req->result);

          }

        }

      }

    } else {

      for (auto& [req, blob_contents] : _blob_reqs) {

        assert(req);

        if (req->status->ok()) {

          PinOwnedBlob(&blob_contents, req->result);

        }

      }

    }

    total_bytes += _bytes_read;

    if (bytes_read) {

      *bytes_read = total_bytes;

    }

  }

}

bool BlobSource::TEST_BlobInCache(uint64_t file_number, uint64_t file_size,

                                  uint64_t offset, size_t* charge) const {

  const CacheKey cache_key = GetCacheKey(file_number, file_size, offset);

  const Slice key = cache_key.AsSlice();

  CacheHandleGuard<BlobContents> blob_handle;

  const Status s = GetBlobFromCache(key, &blob_handle);

  if (s.ok() && blob_handle.GetValue() != nullptr) {

    if (charge) {

      const Cache* const cache = blob_handle.GetCache();

      assert(cache);

      Cache::Handle* const handle = blob_handle.GetCacheHandle();

      assert(handle);

      *charge = cache->GetUsage(handle);

    }

    return true;

  }

  return false;

}

}  // namespace ROCKSDB_NAMESPACE