db_impl_open.cc

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the root directory of this source tree. An additional grant
//  of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/db_impl.h"

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif
#include <inttypes.h>

#include "db/builder.h"
#include "options/options_helper.h"
#include "rocksdb/wal_filter.h"
#include "util/sst_file_manager_impl.h"
#include "util/sync_point.h"

namespace rocksdb {
Options SanitizeOptions(const std::string& dbname,
                        const Options& src) {
  auto db_options = SanitizeOptions(dbname, DBOptions(src));
  ImmutableDBOptions immutable_db_options(db_options);
  auto cf_options =
      SanitizeOptions(immutable_db_options, ColumnFamilyOptions(src));
  return Options(db_options, cf_options);
}

DBOptions SanitizeOptions(const std::string& dbname, const DBOptions& src) {
  DBOptions result(src);

  // result.max_open_files means an "infinite" open files.
  if (result.max_open_files != -1) {
    int max_max_open_files = port::GetMaxOpenFiles();
    if (max_max_open_files == -1) {
      max_max_open_files = 1000000;
    }
    ClipToRange(&result.max_open_files, 20, max_max_open_files);
  }

  if (result.info_log == nullptr) {
    Status s = CreateLoggerFromOptions(dbname, result, &result.info_log);
    if (!s.ok()) {
      // No place suitable for logging
      result.info_log = nullptr;
    }
  }

  if (!result.write_buffer_manager) {
    result.write_buffer_manager.reset(
        new WriteBufferManager(result.db_write_buffer_size));
  }
  if (result.base_background_compactions == -1) {
    result.base_background_compactions = result.max_background_compactions;
  }
  if (result.base_background_compactions > result.max_background_compactions) {
    result.base_background_compactions = result.max_background_compactions;
  }
  result.env->IncBackgroundThreadsIfNeeded(src.max_background_compactions,
                                           Env::Priority::LOW);
  result.env->IncBackgroundThreadsIfNeeded(src.max_background_flushes,
                                           Env::Priority::HIGH);

  if (result.rate_limiter.get() != nullptr) {
    if (result.bytes_per_sync == 0) {
      result.bytes_per_sync = 1024 * 1024;
    }
  }

  if (result.WAL_ttl_seconds > 0 || result.WAL_size_limit_MB > 0) {
    result.recycle_log_file_num = false;
  }

  if (result.recycle_log_file_num &&
      (result.wal_recovery_mode == WALRecoveryMode::kPointInTimeRecovery ||
       result.wal_recovery_mode == WALRecoveryMode::kAbsoluteConsistency)) {
    // kPointInTimeRecovery is indistinguishable from
    // kTolerateCorruptedTailRecords in recycle mode since we define
    // the "end" of the log as the first corrupt record we encounter.
    // kAbsoluteConsistency doesn't make sense because even a clean
    // shutdown leaves old junk at the end of the log file.
    result.wal_recovery_mode = WALRecoveryMode::kTolerateCorruptedTailRecords;
  }

  if (result.wal_dir.empty()) {
    // Use dbname as default
    result.wal_dir = dbname;
  }
  if (result.wal_dir.back() == '/') {
    result.wal_dir = result.wal_dir.substr(0, result.wal_dir.size() - 1);
  }

  if (result.db_paths.size() == 0) {
    result.db_paths.emplace_back(dbname, std::numeric_limits<uint64_t>::max());
  }

  if (result.use_direct_reads && result.compaction_readahead_size == 0) {
    result.compaction_readahead_size = 1024 * 1024 * 2;
  }

  if (result.compaction_readahead_size > 0 ||
      result.use_direct_io_for_flush_and_compaction) {
    result.new_table_reader_for_compaction_inputs = true;
  }

  // Force flush on DB open if 2PC is enabled, since with 2PC we have no
  // guarantee that consecutive log files have consecutive sequence id, which
  // make recovery complicated.
  if (result.allow_2pc) {
    result.avoid_flush_during_recovery = false;
  }

  return result;
}

namespace {

Status SanitizeOptionsByTable(
    const DBOptions& db_opts,
    const std::vector<ColumnFamilyDescriptor>& column_families) {
  Status s;
  for (auto cf : column_families) {
    s = cf.options.table_factory->SanitizeOptions(db_opts, cf.options);
    if (!s.ok()) {
      return s;
    }
  }
  return Status::OK();
}

static Status ValidateOptions(
    const DBOptions& db_options,
    const std::vector<ColumnFamilyDescriptor>& column_families) {
  Status s;

  for (auto& cfd : column_families) {
    s = CheckCompressionSupported(cfd.options);
    if (s.ok() && db_options.allow_concurrent_memtable_write) {
      s = CheckConcurrentWritesSupported(cfd.options);
    }
    if (!s.ok()) {
      return s;
    }
    if (db_options.db_paths.size() > 1) {
      if ((cfd.options.compaction_style != kCompactionStyleUniversal) &&
          (cfd.options.compaction_style != kCompactionStyleLevel)) {
        return Status::NotSupported(
            "More than one DB paths are only supported in "
            "universal and level compaction styles. ");
      }
    }
  }

  if (db_options.db_paths.size() > 4) {
    return Status::NotSupported(
        "More than four DB paths are not supported yet. ");
  }

  if (db_options.allow_mmap_reads && db_options.use_direct_reads) {
    // Protect against assert in PosixMMapReadableFile constructor
    return Status::NotSupported(
        "If memory mapped reads (allow_mmap_reads) are enabled "
        "then direct I/O reads (use_direct_reads) must be disabled. ");
  }

  if (db_options.allow_mmap_writes &&
      db_options.use_direct_io_for_flush_and_compaction) {
    return Status::NotSupported(
        "If memory mapped writes (allow_mmap_writes) are enabled "
        "then direct I/O writes (use_direct_io_for_flush_and_compaction) must "
        "be disabled. ");
  }

  if (db_options.keep_log_file_num == 0) {
    return Status::InvalidArgument("keep_log_file_num must be greater than 0");
  }

  return Status::OK();
}
} // namespace
Status DBImpl::NewDB() {
  VersionEdit new_db;
  new_db.SetLogNumber(0);
  new_db.SetNextFile(2);
  new_db.SetLastSequence(0);

  Status s;

  ROCKS_LOG_INFO(immutable_db_options_.info_log, "Creating manifest 1 \n");
  const std::string manifest = DescriptorFileName(dbname_, 1);
  {
    unique_ptr<WritableFile> file;
    EnvOptions env_options = env_->OptimizeForManifestWrite(env_options_);
    s = NewWritableFile(env_, manifest, &file, env_options);
    if (!s.ok()) {
      return s;
    }
    file->SetPreallocationBlockSize(
        immutable_db_options_.manifest_preallocation_size);
    unique_ptr<WritableFileWriter> file_writer(
        new WritableFileWriter(std::move(file), env_options));
    log::Writer log(std::move(file_writer), 0, false);
    std::string record;
    new_db.EncodeTo(&record);
    s = log.AddRecord(record);
    if (s.ok()) {
      s = SyncManifest(env_, &immutable_db_options_, log.file());
    }
  }
  if (s.ok()) {
    // Make "CURRENT" file that points to the new manifest file.
    s = SetCurrentFile(env_, dbname_, 1, directories_.GetDbDir());
  } else {
    env_->DeleteFile(manifest);
  }
  return s;
}

Status DBImpl::Directories::CreateAndNewDirectory(
    Env* env, const std::string& dirname,
    std::unique_ptr<Directory>* directory) const {
  // We call CreateDirIfMissing() as the directory may already exist (if we
  // are reopening a DB), when this happens we don't want creating the
  // directory to cause an error. However, we need to check if creating the
  // directory fails or else we may get an obscure message about the lock
  // file not existing. One real-world example of this occurring is if
  // env->CreateDirIfMissing() doesn't create intermediate directories, e.g.
  // when dbname_ is "dir/db" but when "dir" doesn't exist.
  Status s = env->CreateDirIfMissing(dirname);
  if (!s.ok()) {
    return s;
  }
  return env->NewDirectory(dirname, directory);
}

Status DBImpl::Directories::SetDirectories(
    Env* env, const std::string& dbname, const std::string& wal_dir,
    const std::vector<DbPath>& data_paths) {
  Status s = CreateAndNewDirectory(env, dbname, &db_dir_);
  if (!s.ok()) {
    return s;
  }
  if (!wal_dir.empty() && dbname != wal_dir) {
    s = CreateAndNewDirectory(env, wal_dir, &wal_dir_);
    if (!s.ok()) {
      return s;
    }
  }

  data_dirs_.clear();
  for (auto& p : data_paths) {
    const std::string db_path = p.path;
    if (db_path == dbname) {
      data_dirs_.emplace_back(nullptr);
    } else {
      std::unique_ptr<Directory> path_directory;
      s = CreateAndNewDirectory(env, db_path, &path_directory);
      if (!s.ok()) {
        return s;
      }
      data_dirs_.emplace_back(path_directory.release());
    }
  }
  assert(data_dirs_.size() == data_paths.size());
  return Status::OK();
}

Status DBImpl::Recover(
    const std::vector<ColumnFamilyDescriptor>& column_families, bool read_only,
    bool error_if_log_file_exist, bool error_if_data_exists_in_logs) {
  mutex_.AssertHeld();

  bool is_new_db = false;
  assert(db_lock_ == nullptr);
  if (!read_only) {
    Status s = directories_.SetDirectories(env_, dbname_,
                                           immutable_db_options_.wal_dir,
                                           immutable_db_options_.db_paths);
    if (!s.ok()) {
      return s;
    }

    s = env_->LockFile(LockFileName(dbname_), &db_lock_);
    if (!s.ok()) {
      return s;
    }

    s = env_->FileExists(CurrentFileName(dbname_));
    if (s.IsNotFound()) {
      if (immutable_db_options_.create_if_missing) {
        s = NewDB();
        is_new_db = true;
        if (!s.ok()) {
          return s;
        }
      } else {
        return Status::InvalidArgument(
            dbname_, "does not exist (create_if_missing is false)");
      }
    } else if (s.ok()) {
      if (immutable_db_options_.error_if_exists) {
        return Status::InvalidArgument(
            dbname_, "exists (error_if_exists is true)");
      }
    } else {
      // Unexpected error reading file
      assert(s.IsIOError());
      return s;
    }
    // Check for the IDENTITY file and create it if not there
    s = env_->FileExists(IdentityFileName(dbname_));
    if (s.IsNotFound()) {
      s = SetIdentityFile(env_, dbname_);
      if (!s.ok()) {
        return s;
      }
    } else if (!s.ok()) {
      assert(s.IsIOError());
      return s;
    }
  }

  Status s = versions_->Recover(column_families, read_only);
  if (immutable_db_options_.paranoid_checks && s.ok()) {
    s = CheckConsistency();
  }
  if (s.ok()) {
    SequenceNumber next_sequence(kMaxSequenceNumber);
    default_cf_handle_ = new ColumnFamilyHandleImpl(
        versions_->GetColumnFamilySet()->GetDefault(), this, &mutex_);
    default_cf_internal_stats_ = default_cf_handle_->cfd()->internal_stats();
    single_column_family_mode_ =
        versions_->GetColumnFamilySet()->NumberOfColumnFamilies() == 1;

    // Recover from all newer log files than the ones named in the
    // descriptor (new log files may have been added by the previous
    // incarnation without registering them in the descriptor).
    //
    // Note that prev_log_number() is no longer used, but we pay
    // attention to it in case we are recovering a database
    // produced by an older version of rocksdb.
    std::vector<std::string> filenames;
    s = env_->GetChildren(immutable_db_options_.wal_dir, &filenames);
    if (!s.ok()) {
      return s;
    }

    std::vector<uint64_t> logs;
    for (size_t i = 0; i < filenames.size(); i++) {
      uint64_t number;
      FileType type;
      if (ParseFileName(filenames[i], &number, &type) && type == kLogFile) {
        if (is_new_db) {
          return Status::Corruption(
              "While creating a new Db, wal_dir contains "
              "existing log file: ",
              filenames[i]);
        } else {
          logs.push_back(number);
        }
      }
    }

    if (logs.size() > 0) {
      if (error_if_log_file_exist) {
        return Status::Corruption(
            "The db was opened in readonly mode with error_if_log_file_exist"
            "flag but a log file already exists");
      } else if (error_if_data_exists_in_logs) {
        for (auto& log : logs) {
          std::string fname = LogFileName(immutable_db_options_.wal_dir, log);
          uint64_t bytes;
          s = env_->GetFileSize(fname, &bytes);
          if (s.ok()) {
            if (bytes > 0) {
              return Status::Corruption(
                  "error_if_data_exists_in_logs is set but there are data "
                  " in log files.");
            }
          }
        }
      }
    }

    if (!logs.empty()) {
      // Recover in the order in which the logs were generated
      std::sort(logs.begin(), logs.end());
      s = RecoverLogFiles(logs, &next_sequence, read_only);
      if (!s.ok()) {
        // Clear memtables if recovery failed
        for (auto cfd : *versions_->GetColumnFamilySet()) {
          cfd->CreateNewMemtable(*cfd->GetLatestMutableCFOptions(),
                                 kMaxSequenceNumber);
        }
      }
    }
  }

  // Initial value
  max_total_in_memory_state_ = 0;
  for (auto cfd : *versions_->GetColumnFamilySet()) {
    auto* mutable_cf_options = cfd->GetLatestMutableCFOptions();
    max_total_in_memory_state_ += mutable_cf_options->write_buffer_size *
                                  mutable_cf_options->max_write_buffer_number;
  }

  return s;
}

// REQUIRES: log_numbers are sorted in ascending order
Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
                               SequenceNumber* next_sequence, bool read_only) {
  struct LogReporter : public log::Reader::Reporter {
    Env* env;
    Logger* info_log;
    const char* fname;
    Status* status;  // nullptr if immutable_db_options_.paranoid_checks==false
    virtual void Corruption(size_t bytes, const Status& s) override {
      ROCKS_LOG_WARN(info_log, "%s%s: dropping %d bytes; %s",
                     (this->status == nullptr ? "(ignoring error) " : ""),
                     fname, static_cast<int>(bytes), s.ToString().c_str());
      if (this->status != nullptr && this->status->ok()) {
        *this->status = s;
      }
    }
  };

  mutex_.AssertHeld();
  Status status;
  std::unordered_map<int, VersionEdit> version_edits;
  // no need to refcount because iteration is under mutex
  for (auto cfd : *versions_->GetColumnFamilySet()) {
    VersionEdit edit;
    edit.SetColumnFamily(cfd->GetID());
    version_edits.insert({cfd->GetID(), edit});
  }
  int job_id = next_job_id_.fetch_add(1);
  {
    auto stream = event_logger_.Log();
    stream << "job" << job_id << "event"
           << "recovery_started";
    stream << "log_files";
    stream.StartArray();
    for (auto log_number : log_numbers) {
      stream << log_number;
    }
    stream.EndArray();
  }

#ifndef ROCKSDB_LITE
  if (immutable_db_options_.wal_filter != nullptr) {
    std::map<std::string, uint32_t> cf_name_id_map;
    std::map<uint32_t, uint64_t> cf_lognumber_map;
    for (auto cfd : *versions_->GetColumnFamilySet()) {
      cf_name_id_map.insert(
        std::make_pair(cfd->GetName(), cfd->GetID()));
      cf_lognumber_map.insert(
        std::make_pair(cfd->GetID(), cfd->GetLogNumber()));
    }

    immutable_db_options_.wal_filter->ColumnFamilyLogNumberMap(cf_lognumber_map,
                                                               cf_name_id_map);
  }
#endif

  bool stop_replay_by_wal_filter = false;
  bool stop_replay_for_corruption = false;
  bool flushed = false;
  for (auto log_number : log_numbers) {
    // The previous incarnation may not have written any MANIFEST
    // records after allocating this log number.  So we manually
    // update the file number allocation counter in VersionSet.
    versions_->MarkFileNumberUsedDuringRecovery(log_number);
    // Open the log file
    std::string fname = LogFileName(immutable_db_options_.wal_dir, log_number);

    ROCKS_LOG_INFO(immutable_db_options_.info_log,
                   "Recovering log #%" PRIu64 " mode %d", log_number,
                   immutable_db_options_.wal_recovery_mode);
    auto logFileDropped = [this, &fname]() {
      uint64_t bytes;
      if (env_->GetFileSize(fname, &bytes).ok()) {
        auto info_log = immutable_db_options_.info_log.get();
        ROCKS_LOG_WARN(info_log, "%s: dropping %d bytes", fname.c_str(),
                       static_cast<int>(bytes));
      }
    };
    if (stop_replay_by_wal_filter) {
      logFileDropped();
      continue;
    }

    unique_ptr<SequentialFileReader> file_reader;
    {
      unique_ptr<SequentialFile> file;
      status = env_->NewSequentialFile(fname, &file, env_options_);
      if (!status.ok()) {
        MaybeIgnoreError(&status);
        if (!status.ok()) {
          return status;
        } else {
          // Fail with one log file, but that's ok.
          // Try next one.
          continue;
        }
      }
      file_reader.reset(new SequentialFileReader(std::move(file)));
    }

    // Create the log reader.
    LogReporter reporter;
    reporter.env = env_;
    reporter.info_log = immutable_db_options_.info_log.get();
    reporter.fname = fname.c_str();
    if (!immutable_db_options_.paranoid_checks ||
        immutable_db_options_.wal_recovery_mode ==
            WALRecoveryMode::kSkipAnyCorruptedRecords) {
      reporter.status = nullptr;
    } else {
      reporter.status = &status;
    }
    // We intentially make log::Reader do checksumming even if
    // paranoid_checks==false so that corruptions cause entire commits
    // to be skipped instead of propagating bad information (like overly
    // large sequence numbers).
    log::Reader reader(immutable_db_options_.info_log, std::move(file_reader),
                       &reporter, true /*checksum*/, 0 /*initial_offset*/,
                       log_number);

    // Determine if we should tolerate incomplete records at the tail end of the
    // Read all the records and add to a memtable
    std::string scratch;
    Slice record;
    WriteBatch batch;

    while (!stop_replay_by_wal_filter &&
           reader.ReadRecord(&record, &scratch,
                             immutable_db_options_.wal_recovery_mode) &&
           status.ok()) {
      if (record.size() < WriteBatchInternal::kHeader) {
        reporter.Corruption(record.size(),
                            Status::Corruption("log record too small"));
        continue;
      }
      WriteBatchInternal::SetContents(&batch, record);
      SequenceNumber sequence = WriteBatchInternal::Sequence(&batch);

      if (immutable_db_options_.wal_recovery_mode ==
          WALRecoveryMode::kPointInTimeRecovery) {
        // In point-in-time recovery mode, if sequence id of log files are
        // consecutive, we continue recovery despite corruption. This could
        // happen when we open and write to a corrupted DB, where sequence id
        // will start from the last sequence id we recovered.
        if (sequence == *next_sequence) {
          stop_replay_for_corruption = false;
        }
        if (stop_replay_for_corruption) {
          logFileDropped();
          break;
        }
      }

#ifndef ROCKSDB_LITE
      if (immutable_db_options_.wal_filter != nullptr) {
        WriteBatch new_batch;
        bool batch_changed = false;

        WalFilter::WalProcessingOption wal_processing_option =
            immutable_db_options_.wal_filter->LogRecordFound(
                log_number, fname, batch, &new_batch, &batch_changed);

        switch (wal_processing_option) {
          case WalFilter::WalProcessingOption::kContinueProcessing:
            // do nothing, proceeed normally
            break;
          case WalFilter::WalProcessingOption::kIgnoreCurrentRecord:
            // skip current record
            continue;
          case WalFilter::WalProcessingOption::kStopReplay:
            // skip current record and stop replay
            stop_replay_by_wal_filter = true;
            continue;
          case WalFilter::WalProcessingOption::kCorruptedRecord: {
            status =
                Status::Corruption("Corruption reported by Wal Filter ",
                                   immutable_db_options_.wal_filter->Name());
            MaybeIgnoreError(&status);
            if (!status.ok()) {
              reporter.Corruption(record.size(), status);
              continue;
            }
            break;
          }
          default: {
            assert(false);  // unhandled case
            status = Status::NotSupported(
                "Unknown WalProcessingOption returned"
                " by Wal Filter ",
                immutable_db_options_.wal_filter->Name());
            MaybeIgnoreError(&status);
            if (!status.ok()) {
              return status;
            } else {
              // Ignore the error with current record processing.
              continue;
            }
          }
        }

        if (batch_changed) {
          // Make sure that the count in the new batch is
          // within the orignal count.
          int new_count = WriteBatchInternal::Count(&new_batch);
          int original_count = WriteBatchInternal::Count(&batch);
          if (new_count > original_count) {
            ROCKS_LOG_FATAL(
                immutable_db_options_.info_log,
                "Recovering log #%" PRIu64
                " mode %d log filter %s returned "
                "more records (%d) than original (%d) which is not allowed. "
                "Aborting recovery.",
                log_number, immutable_db_options_.wal_recovery_mode,
                immutable_db_options_.wal_filter->Name(), new_count,
                original_count);
            status = Status::NotSupported(
                "More than original # of records "
                "returned by Wal Filter ",
                immutable_db_options_.wal_filter->Name());
            return status;
          }
          // Set the same sequence number in the new_batch
          // as the original batch.
          WriteBatchInternal::SetSequence(&new_batch,
                                          WriteBatchInternal::Sequence(&batch));
          batch = new_batch;
        }
      }
#endif  // ROCKSDB_LITE

      // If column family was not found, it might mean that the WAL write
      // batch references to the column family that was dropped after the
      // insert. We don't want to fail the whole write batch in that case --
      // we just ignore the update.
      // That's why we set ignore missing column families to true
      bool has_valid_writes = false;
      status = WriteBatchInternal::InsertInto(
          &batch, column_family_memtables_.get(), &flush_scheduler_, true,
          log_number, this, false /* concurrent_memtable_writes */,
          next_sequence, &has_valid_writes);
      MaybeIgnoreError(&status);
      if (!status.ok()) {
        // We are treating this as a failure while reading since we read valid
        // blocks that do not form coherent data
        reporter.Corruption(record.size(), status);
        continue;
      }

      if (has_valid_writes && !read_only) {
        // we can do this because this is called before client has access to the
        // DB and there is only a single thread operating on DB
        ColumnFamilyData* cfd;

        while ((cfd = flush_scheduler_.TakeNextColumnFamily()) != nullptr) {
          cfd->Unref();
          // If this asserts, it means that InsertInto failed in
          // filtering updates to already-flushed column families
          assert(cfd->GetLogNumber() <= log_number);
          auto iter = version_edits.find(cfd->GetID());
          assert(iter != version_edits.end());
          VersionEdit* edit = &iter->second;
          status = WriteLevel0TableForRecovery(job_id, cfd, cfd->mem(), edit);
          if (!status.ok()) {
            // Reflect errors immediately so that conditions like full
            // file-systems cause the DB::Open() to fail.
            return status;
          }
          flushed = true;

          cfd->CreateNewMemtable(*cfd->GetLatestMutableCFOptions(),
                                 *next_sequence);
        }
      }
    }

    if (!status.ok()) {
      if (immutable_db_options_.wal_recovery_mode ==
          WALRecoveryMode::kSkipAnyCorruptedRecords) {
        // We should ignore all errors unconditionally
        status = Status::OK();
      } else if (immutable_db_options_.wal_recovery_mode ==
                 WALRecoveryMode::kPointInTimeRecovery) {
        // We should ignore the error but not continue replaying
        status = Status::OK();
        stop_replay_for_corruption = true;
        ROCKS_LOG_INFO(immutable_db_options_.info_log,
                       "Point in time recovered to log #%" PRIu64
                       " seq #%" PRIu64,
                       log_number, *next_sequence);
      } else {
        assert(immutable_db_options_.wal_recovery_mode ==
                   WALRecoveryMode::kTolerateCorruptedTailRecords ||
               immutable_db_options_.wal_recovery_mode ==
                   WALRecoveryMode::kAbsoluteConsistency);
        return status;
      }
    }

    flush_scheduler_.Clear();
    auto last_sequence = *next_sequence - 1;
    if ((*next_sequence != kMaxSequenceNumber) &&
        (versions_->LastSequence() <= last_sequence)) {
      versions_->SetLastSequence(last_sequence);
    }
  }

  // True if there's any data in the WALs; if not, we can skip re-processing
  // them later
  bool data_seen = false;
  if (!read_only) {
    // no need to refcount since client still doesn't have access
    // to the DB and can not drop column families while we iterate
    auto max_log_number = log_numbers.back();
    for (auto cfd : *versions_->GetColumnFamilySet()) {
      auto iter = version_edits.find(cfd->GetID());
      assert(iter != version_edits.end());
      VersionEdit* edit = &iter->second;

      if (cfd->GetLogNumber() > max_log_number) {
        // Column family cfd has already flushed the data
        // from all logs. Memtable has to be empty because
        // we filter the updates based on log_number
        // (in WriteBatch::InsertInto)
        assert(cfd->mem()->GetFirstSequenceNumber() == 0);
        assert(edit->NumEntries() == 0);
        continue;
      }

      // flush the final memtable (if non-empty)
      if (cfd->mem()->GetFirstSequenceNumber() != 0) {
        // If flush happened in the middle of recovery (e.g. due to memtable
        // being full), we flush at the end. Otherwise we'll need to record
        // where we were on last flush, which make the logic complicated.
        if (flushed || !immutable_db_options_.avoid_flush_during_recovery) {
          status = WriteLevel0TableForRecovery(job_id, cfd, cfd->mem(), edit);
          if (!status.ok()) {
            // Recovery failed
            break;
          }
          flushed = true;

          cfd->CreateNewMemtable(*cfd->GetLatestMutableCFOptions(),
                                 versions_->LastSequence());
        }
        data_seen = true;
      }

      // write MANIFEST with update
      // writing log_number in the manifest means that any log file
      // with number strongly less than (log_number + 1) is already
      // recovered and should be ignored on next reincarnation.
      // Since we already recovered max_log_number, we want all logs
      // with numbers `<= max_log_number` (includes this one) to be ignored
      if (flushed || cfd->mem()->GetFirstSequenceNumber() == 0) {
        edit->SetLogNumber(max_log_number + 1);
      }
      // we must mark the next log number as used, even though it's
      // not actually used. that is because VersionSet assumes
      // VersionSet::next_file_number_ always to be strictly greater than any
      // log number
      versions_->MarkFileNumberUsedDuringRecovery(max_log_number + 1);
      status = versions_->LogAndApply(
          cfd, *cfd->GetLatestMutableCFOptions(), edit, &mutex_);
      if (!status.ok()) {
        // Recovery failed
        break;
      }
    }
  }

  if (data_seen && !flushed) {
    // Mark these as alive so they'll be considered for deletion later by
    // FindObsoleteFiles()
    for (auto log_number : log_numbers) {
      alive_log_files_.push_back(LogFileNumberSize(log_number));
    }
  }

  event_logger_.Log() << "job" << job_id << "event"
                      << "recovery_finished";

  return status;
}

Status DBImpl::WriteLevel0TableForRecovery(int job_id, ColumnFamilyData* cfd,
                                           MemTable* mem, VersionEdit* edit) {
  mutex_.AssertHeld();
  const uint64_t start_micros = env_->NowMicros();
  FileMetaData meta;
  auto pending_outputs_inserted_elem =
      CaptureCurrentFileNumberInPendingOutputs();
  meta.fd = FileDescriptor(versions_->NewFileNumber(), 0, 0);
  ReadOptions ro;
  ro.total_order_seek = true;
  Arena arena;
  Status s;
  TableProperties table_properties;
  {
    ScopedArenaIterator iter(mem->NewIterator(ro, &arena));
    ROCKS_LOG_DEBUG(immutable_db_options_.info_log,
                    "[%s] [WriteLevel0TableForRecovery]"
                    " Level-0 table #%" PRIu64 ": started",
                    cfd->GetName().c_str(), meta.fd.GetNumber());

    // Get the latest mutable cf options while the mutex is still locked
    const MutableCFOptions mutable_cf_options =
        *cfd->GetLatestMutableCFOptions();
    bool paranoid_file_checks =
        cfd->GetLatestMutableCFOptions()->paranoid_file_checks;
    {
      mutex_.Unlock();

      SequenceNumber earliest_write_conflict_snapshot;
      std::vector<SequenceNumber> snapshot_seqs =
          snapshots_.GetAll(&earliest_write_conflict_snapshot);

      EnvOptions optimized_env_options =
          env_->OptimizeForCompactionTableWrite(env_options_, immutable_db_options_);
      s = BuildTable(
          dbname_, env_, *cfd->ioptions(), mutable_cf_options,
          optimized_env_options, cfd->table_cache(), iter.get(),
          std::unique_ptr<InternalIterator>(mem->NewRangeTombstoneIterator(ro)),
          &meta, cfd->internal_comparator(),
          cfd->int_tbl_prop_collector_factories(), cfd->GetID(), cfd->GetName(),
          snapshot_seqs, earliest_write_conflict_snapshot,
          GetCompressionFlush(*cfd->ioptions(), mutable_cf_options),
          cfd->ioptions()->compression_opts, paranoid_file_checks,
          cfd->internal_stats(), TableFileCreationReason::kRecovery,
          &event_logger_, job_id);
      LogFlush(immutable_db_options_.info_log);
      ROCKS_LOG_DEBUG(immutable_db_options_.info_log,
                      "[%s] [WriteLevel0TableForRecovery]"
                      " Level-0 table #%" PRIu64 ": %" PRIu64 " bytes %s",
                      cfd->GetName().c_str(), meta.fd.GetNumber(),
                      meta.fd.GetFileSize(), s.ToString().c_str());
      mutex_.Lock();
    }
  }
  ReleaseFileNumberFromPendingOutputs(pending_outputs_inserted_elem);

  // Note that if file_size is zero, the file has been deleted and
  // should not be added to the manifest.
  int level = 0;
  if (s.ok() && meta.fd.GetFileSize() > 0) {
    edit->AddFile(level, meta.fd.GetNumber(), meta.fd.GetPathId(),
                  meta.fd.GetFileSize(), meta.smallest, meta.largest,
                  meta.smallest_seqno, meta.largest_seqno,
                  meta.marked_for_compaction);
  }

  InternalStats::CompactionStats stats(1);
  stats.micros = env_->NowMicros() - start_micros;
  stats.bytes_written = meta.fd.GetFileSize();
  stats.num_output_files = 1;
  cfd->internal_stats()->AddCompactionStats(level, stats);
  cfd->internal_stats()->AddCFStats(
      InternalStats::BYTES_FLUSHED, meta.fd.GetFileSize());
  RecordTick(stats_, COMPACT_WRITE_BYTES, meta.fd.GetFileSize());
  return s;
}

Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
  DBOptions db_options(options);
  ColumnFamilyOptions cf_options(options);
  std::vector<ColumnFamilyDescriptor> column_families;
  column_families.push_back(
      ColumnFamilyDescriptor(kDefaultColumnFamilyName, cf_options));
  std::vector<ColumnFamilyHandle*> handles;
  Status s = DB::Open(db_options, dbname, column_families, &handles, dbptr);
  if (s.ok()) {
    assert(handles.size() == 1);
    // i can delete the handle since DBImpl is always holding a reference to
    // default column family
    delete handles[0];
  }
  return s;
}
  
Status DB::Open(const DBOptions& db_options, const std::string& dbname,
                const std::vector<ColumnFamilyDescriptor>& column_families,
                std::vector<ColumnFamilyHandle*>* handles, DB** dbptr) {
  Status s = SanitizeOptionsByTable(db_options, column_families);
  if (!s.ok()) {
    return s;
  }

  s = ValidateOptions(db_options, column_families);
  if (!s.ok()) {
    return s;
  }

  *dbptr = nullptr;
  handles->clear();

  size_t max_write_buffer_size = 0;
  for (auto cf : column_families) {
    max_write_buffer_size =
        std::max(max_write_buffer_size, cf.options.write_buffer_size);
  }

  DBImpl* impl = new DBImpl(db_options, dbname);
  s = impl->env_->CreateDirIfMissing(impl->immutable_db_options_.wal_dir);
  if (s.ok()) {
    for (auto db_path : impl->immutable_db_options_.db_paths) {
      s = impl->env_->CreateDirIfMissing(db_path.path);
      if (!s.ok()) {
        break;
      }
    }
  }

  if (!s.ok()) {
    delete impl;
    return s;
  }

  s = impl->CreateArchivalDirectory();
  if (!s.ok()) {
    delete impl;
    return s;
  }
  impl->mutex_.Lock();
  // Handles create_if_missing, error_if_exists
  s = impl->Recover(column_families);
  if (s.ok()) {
    uint64_t new_log_number = impl->versions_->NewFileNumber();
    unique_ptr<WritableFile> lfile;
    EnvOptions soptions(db_options);
    EnvOptions opt_env_options =
        impl->immutable_db_options_.env->OptimizeForLogWrite(
            soptions, BuildDBOptions(impl->immutable_db_options_,
                                     impl->mutable_db_options_));
    s = NewWritableFile(
        impl->immutable_db_options_.env,
        LogFileName(impl->immutable_db_options_.wal_dir, new_log_number),
        &lfile, opt_env_options);
    if (s.ok()) {
      lfile->SetPreallocationBlockSize(
          impl->GetWalPreallocateBlockSize(max_write_buffer_size));
      impl->logfile_number_ = new_log_number;
      unique_ptr<WritableFileWriter> file_writer(
          new WritableFileWriter(std::move(lfile), opt_env_options));
      impl->logs_.emplace_back(
          new_log_number,
          new log::Writer(
              std::move(file_writer), new_log_number,
              impl->immutable_db_options_.recycle_log_file_num > 0));

      // set column family handles
      for (auto cf : column_families) {
        auto cfd =
            impl->versions_->GetColumnFamilySet()->GetColumnFamily(cf.name);
        if (cfd != nullptr) {
          handles->push_back(
              new ColumnFamilyHandleImpl(cfd, impl, &impl->mutex_));
          impl->NewThreadStatusCfInfo(cfd);
        } else {
          if (db_options.create_missing_column_families) {
            // missing column family, create it
            ColumnFamilyHandle* handle;
            impl->mutex_.Unlock();
            s = impl->CreateColumnFamily(cf.options, cf.name, &handle);
            impl->mutex_.Lock();
            if (s.ok()) {
              handles->push_back(handle);
            } else {
              break;
            }
          } else {
            s = Status::InvalidArgument("Column family not found: ", cf.name);
            break;
          }
        }
      }
    }
    if (s.ok()) {
      for (auto cfd : *impl->versions_->GetColumnFamilySet()) {
        delete impl->InstallSuperVersionAndScheduleWork(
            cfd, nullptr, *cfd->GetLatestMutableCFOptions());
      }
      impl->alive_log_files_.push_back(
          DBImpl::LogFileNumberSize(impl->logfile_number_));
      impl->DeleteObsoleteFiles();
      s = impl->directories_.GetDbDir()->Fsync();
    }
  }

  if (s.ok()) {
    for (auto cfd : *impl->versions_->GetColumnFamilySet()) {
      if (cfd->ioptions()->compaction_style == kCompactionStyleFIFO) {
        auto* vstorage = cfd->current()->storage_info();
        for (int i = 1; i < vstorage->num_levels(); ++i) {
          int num_files = vstorage->NumLevelFiles(i);
          if (num_files > 0) {
            s = Status::InvalidArgument(
                "Not all files are at level 0. Cannot "
                "open with FIFO compaction style.");
            break;
          }
        }
      }
      if (!cfd->mem()->IsSnapshotSupported()) {
        impl->is_snapshot_supported_ = false;
      }
      if (cfd->ioptions()->merge_operator != nullptr &&
          !cfd->mem()->IsMergeOperatorSupported()) {
        s = Status::InvalidArgument(
            "The memtable of column family %s does not support merge operator "
            "its options.merge_operator is non-null", cfd->GetName().c_str());
      }
      if (!s.ok()) {
        break;
      }
    }
  }
  TEST_SYNC_POINT("DBImpl::Open:Opened");
  Status persist_options_status;
  if (s.ok()) {
    // Persist RocksDB Options before scheduling the compaction.
    // The WriteOptionsFile() will release and lock the mutex internally.
    persist_options_status = impl->WriteOptionsFile();

    *dbptr = impl;
    impl->opened_successfully_ = true;
    impl->MaybeScheduleFlushOrCompaction();
  }
  impl->mutex_.Unlock();

#ifndef ROCKSDB_LITE
  auto sfm = static_cast<SstFileManagerImpl*>(
      impl->immutable_db_options_.sst_file_manager.get());
  if (s.ok() && sfm) {
    // Notify SstFileManager about all sst files that already exist in
    // db_paths[0] when the DB is opened.
    auto& db_path = impl->immutable_db_options_.db_paths[0];
    std::vector<std::string> existing_files;
    impl->immutable_db_options_.env->GetChildren(db_path.path, &existing_files);
    for (auto& file_name : existing_files) {
      uint64_t file_number;
      FileType file_type;
      std::string file_path = db_path.path + "/" + file_name;
      if (ParseFileName(file_name, &file_number, &file_type) &&
          file_type == kTableFile) {
        sfm->OnAddFile(file_path);
      }
    }
  }
#endif  // !ROCKSDB_LITE

  if (s.ok()) {
    ROCKS_LOG_INFO(impl->immutable_db_options_.info_log, "DB pointer %p", impl);
    LogFlush(impl->immutable_db_options_.info_log);
    if (!persist_options_status.ok()) {
      if (db_options.fail_if_options_file_error) {
        s = Status::IOError(
            "DB::Open() failed --- Unable to persist Options file",
            persist_options_status.ToString());
      }
      ROCKS_LOG_WARN(impl->immutable_db_options_.info_log,
                     "Unable to persist options in DB::Open() -- %s",
                     persist_options_status.ToString().c_str());
    }
  }
  if (!s.ok()) {
    for (auto* h : *handles) {
      delete h;
    }
    handles->clear();
    delete impl;
    *dbptr = nullptr;
  }
  return s;
}
}  // namespace rocksdb