RFC: new rados whereis command

[Loic Dachary <loic@dachary.org>]

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Hi Andreas,

I took a closer look at https://github.com/ceph/ceph/pull/2730 implementing rados whereis [--dns] and I think it deserves a discussion here. If I understand correctly, it relies on a new function of the rados API:

  typedef struct whereis {
    int64_t osd_id;                              //< ID of the OSD hosting this object
    std::string osd_state;                       //< state of the OSD - either 'active' or 'inactive'
    int64_t pg_seed;                             //< Seed of the PG hosting this object
    std::string ip_string;                       //< Ip as string
    std::vector<std::string> host_names;         //< optional reverse DNS HostNames
    std::map<std::string, std::string> user_map; //< optional user KV map
    void resolve();                              //< reverse DNS OSD IPs and store in HostNames
  } whereis_t;

  static int whereis(IoCtx &ioctx, const std::string &oid, std::vector<whereis_t> &locations);

which needs to be added there because the rados API does not expose some details that are needed to fill the fields of the whereis_t structure.

It looks fine to me but ... I'm not used to maintaining or developing the rados API and someone else may have a more informed opinion.

There is a technical detail that also needs to be sorted out : the current implementation exposes the RadosWhereis class (for dump) and this should either be moved to rados.cc or be part of the rados API (which probably is not the best option because it would also expose Formatter as a consequence).

Cheers
-- 
Loïc Dachary, Artisan Logiciel Libre


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