示例#1
0
Try<Action> LevelDBStorage::read(uint64_t position)
{
  Stopwatch stopwatch;
  stopwatch.start();

  leveldb::ReadOptions options;

  string value;

  leveldb::Status status = db->Get(options, encode(position), &value);

  if (!status.ok()) {
    return Error(status.ToString());
  }

  google::protobuf::io::ArrayInputStream stream(value.data(), value.size());

  Record record;

  if (!record.ParseFromZeroCopyStream(&stream)) {
    return Error("Failed to deserialize record");
  }

  if (record.type() != Record::ACTION) {
    return Error("Bad record");
  }

  LOG(INFO) << "Reading position from leveldb took " << stopwatch.elapsed();

  return record.action();
}
示例#2
0
Try<Storage::State> LevelDBStorage::restore(const string& path)
{
  leveldb::Options options;
  options.create_if_missing = true;

  // TODO(benh): Can't use varint comparator until bug discussed at
  // groups.google.com/group/leveldb/browse_thread/thread/17eac39168909ba7
  // gets fixed. For now, we are using the default byte-wise
  // comparator and *assuming* that the encoding from unsigned long to
  // string produces a stable ordering. Checks below.
  // options.comparator = &comparator;

  const string& one = encode(1);
  const string& two = encode(2);
  const string& ten = encode(10);

  CHECK(leveldb::BytewiseComparator()->Compare(one, two) < 0);
  CHECK(leveldb::BytewiseComparator()->Compare(two, one) > 0);
  CHECK(leveldb::BytewiseComparator()->Compare(one, ten) < 0);
  CHECK(leveldb::BytewiseComparator()->Compare(ten, two) > 0);
  CHECK(leveldb::BytewiseComparator()->Compare(ten, ten) == 0);

  Stopwatch stopwatch;
  stopwatch.start();

  leveldb::Status status = leveldb::DB::Open(options, path, &db);

  if (!status.ok()) {
    // TODO(benh): Consider trying to repair the DB.
    return Error(status.ToString());
  }

  LOG(INFO) << "Opened db in " << stopwatch.elapsed();

  stopwatch.start(); // Restart the stopwatch.

  // TODO(benh): Conditionally compact to avoid long recovery times?
  db->CompactRange(nullptr, nullptr);

  LOG(INFO) << "Compacted db in " << stopwatch.elapsed();

  State state;
  state.begin = 0;
  state.end = 0;

  // TODO(benh): Consider just reading the "promise" record (e.g.,
  // 'encode(0, false)') and then iterating over the rest of the
  // records and confirming that they are all indeed of type
  // Record::Action.

  stopwatch.start(); // Restart the stopwatch.

  leveldb::Iterator* iterator = db->NewIterator(leveldb::ReadOptions());

  LOG(INFO) << "Created db iterator in " << stopwatch.elapsed();

  stopwatch.start(); // Restart the stopwatch.

  iterator->SeekToFirst();

  LOG(INFO) << "Seeked to beginning of db in " << stopwatch.elapsed();

  stopwatch.start(); // Restart the stopwatch.

  uint64_t keys = 0;

  while (iterator->Valid()) {
    keys++;
    const leveldb::Slice& slice = iterator->value();

    google::protobuf::io::ArrayInputStream stream(slice.data(), slice.size());

    Record record;

    if (!record.ParseFromZeroCopyStream(&stream)) {
      return Error("Failed to deserialize record");
    }

    switch (record.type()) {
      case Record::METADATA: {
        CHECK(record.has_metadata());
        state.metadata.CopyFrom(record.metadata());
        break;
      }

      // DEPRECATED!
      case Record::PROMISE: {
        CHECK(record.has_promise());
        // This replica is in old format. Set its status to VOTING
        // since there is no catch-up logic in the old code and this
        // replica is obviously not empty.
        state.metadata.set_status(Metadata::VOTING);
        state.metadata.set_promised(record.promise().proposal());
        break;
      }

      case Record::ACTION: {
        CHECK(record.has_action());
        const Action& action = record.action();
        if (action.has_learned() && action.learned()) {
          state.learned.insert(action.position());
          state.unlearned.erase(action.position());
          if (action.has_type() && action.type() == Action::TRUNCATE) {
            state.begin = std::max(state.begin, action.truncate().to());
          }
        } else {
          state.learned.erase(action.position());
          state.unlearned.insert(action.position());
        }
        state.end = std::max(state.end, action.position());

        // Cache the first position in this replica so during a
        // truncation, we can attempt to delete all positions from the
        // first position up to the truncate position. Note that this
        // is not the beginning position of the log, but rather the
        // first position that remains (i.e., hasn't been deleted) in
        // leveldb.
        first = min(first, action.position());
        break;
      }

      default: {
        return Error("Bad record");
      }
    }

    iterator->Next();
  }

  LOG(INFO) << "Iterated through " << keys
            << " keys in the db in " << stopwatch.elapsed();

  delete iterator;

  return state;
}