Method Init

src/leveldb/persistent_cache/persistent_cache_metadata.cc:130–239

}

Status PersistentCacheMetaData::Init(uint64_t* recovered_cache_id, PersistentCacheImpl* cache) {
  Options opt;
  opt.filter_policy = NewBloomFilterPolicy(10);
  opt.block_cache = leveldb::NewLRUCache(8UL * 1024 * 1024);
  opt.table_cache = new leveldb::TableCache(8UL * 1024 * 1024);
  opt.info_log = Logger::DefaultLogger();

  auto lg_info = new leveldb::LG_info(0);
  lg_info->env = NewPosixEnv();
  lg_info->env->SetBackgroundThreads(5);

  opt.lg_info_list = new std::map<uint32_t, leveldb::LG_info*>;
  opt.lg_info_list->insert(std::make_pair(0, lg_info));
  opt.use_file_lock = false;  // Single process access is guaranteed by ts port.

  DB* db;
  auto status = DB::Open(opt, cache->GetMetaPath(), &db);

  if (!status.ok()) {
    LEVELDB_LOG("Open persistent cache metadata failed, reason: %s\n", status.ToString().c_str());
    return status;
  }

  db_.reset(db);

  ReadOptions read_options(&opt);
  read_options.fill_cache = false;
  read_options.verify_checksums = true;
  std::unique_ptr<Iterator> iterator{db_->NewIterator(read_options)};
  iterator->SeekToFirst();
  uint64_t max_cache_id{0};

  //  db format(kv):
  //  key -> file_path
  //  when restore meta data from disk, we get k-v pair from leveldb
  //  where key is the user cache key, and value is file_path in system
  while (iterator->Valid()) {
    const Slice key = iterator->key();
    Slice val = iterator->value();
    assert(val.ends_with(".rc"));

    // path format : /xxx/yyy/zzz/k.cache_id.rc
    // try extract cache_id from path.
    std::string path = val.ToString();
    std::string cache_id_str = path.substr(0, path.size() - 3);
    auto last_point_pos = cache_id_str.find_last_of('.');
    assert(last_point_pos != std::string::npos);
    cache_id_str = cache_id_str.substr(last_point_pos + 1);
    uint64_t cache_id{0};

    try {
      cache_id = std::stoul(cache_id_str);
    } catch (...) {
      LEVELDB_LOG("[%s] Fail to recover cache_id key: %s, value: %s\n",
                  cache->GetCachePath().c_str(), key.ToString().c_str(), val.ToString().c_str());
      db->Delete({}, key);
      continue;
    };