Add cron to recalculate db size

[kinoute]

Following RocksLabs/kvrocks_exporter#25, I was wondering if there is any way to automatically recalculate the db size instead of doing it manually through dbsize scan with the redis-cli. Because without it, the panel on the Grafana dashboard doesn't make any sense without manual intervention, same for the info command through the CLI or redis client.

I thought it would be nice to add a cronjob that could run periodically to run this command on all namespaces to have up-to-date estimated keys number (default: disabled).

This is my first PR here and in C++, I hope I didn't make any mess.

[PragmaTwice]

It generally looks good to me.

[git-hulk]

Generally looks good, you can fix the tidy issue according to https://github.com/apache/kvrocks/actions/runs/8526319228/job/23369018645?pr=2217#step:7:1294

[jihuayu]

Great feature, thank you.

[kinoute]

@git-hulk I pre-allocated the namespaces variable, I don't know if it's alright. Any idea why clang-tidy doesn't raise the same error for the command namespace get * implementation? My PR is based on this: https://github.com/apache/kvrocks/blob/unstable/src/commands/cmd_server.cc#L100-L107

  std::vector<std::string> namespaces;
  auto tokens = srv->GetNamespace()->List();
  for (auto &token : tokens) {
    namespaces.emplace_back(token.second);  // namespace
    namespaces.emplace_back(token.first);   // token
  }
  namespaces.emplace_back(kDefaultNamespace);
  namespaces.emplace_back(config->requirepass);

[git-hulk]

@git-hulk I pre-allocated the namespaces variable, I don't know if it's alright. Any idea why clang-tidy doesn't raise the same error for the command namespace get * implementation? My PR is based on this: https://github.com/apache/kvrocks/blob/unstable/src/commands/cmd_server.cc#L100-L107

  std::vector<std::string> namespaces;
  auto tokens = srv->GetNamespace()->List();
  for (auto &token : tokens) {
    namespaces.emplace_back(token.second);  // namespace
    namespaces.emplace_back(token.first);   // token
  }
  namespaces.emplace_back(kDefaultNamespace);
  namespaces.emplace_back(config->requirepass);

@kinoute That's right to reserve the space for namespaces. And why it doesn't raise an error in the previous codes, is because it's added before introducing the linter.

[git-hulk]

@kinoute Thanks for your contribution.

[sonarcloud]

Quality Gate failed

Failed conditions
49.5% Coverage on New Code (required ≥ 50%)

See analysis details on SonarCloud