NAME

       doc_help_elektra-granularity_md - elektra-granularity.md

elektra-granularity(7) -- relation of keys to files

       Keys of a backend can only be retrieved as a full key set. Currently it is not possible to
       fetch a part of the keys of a backend. So the user needs to cut out the interesting keys
       with ksCut() afterwards. If the keys should be committed again, the whole key set must be
       preserved. Otherwise, the clipped keys will be removed permanently.

       This restriction simplifies storage plugins while it does not limit the user. Other
       plugins would not be able to fulfil their purpose without the full KeySet. For example, a
       plugin that checks the availability and structure of all keys cannot work with a partial
       key set.

       It is problematic to have too many keys in one backend. The applications would need memory
       for unnecessary configuration data. Instead we recommend introducing several mount points
       to split up the keys into different backends. Splitting up key sets makes sense if any
       application requests only a part of the configuration. No benefits arise if every
       application requests all keys anyway.

       Let us assume that many keys reside in user/sw and an application only needs the keys in
       user/sw/app. To save memory and get better startup times for the application, a new
       backend can be mounted at user/sw/app. On the other hand, every mounted backend causes a
       small run time overhead in the overall configuration system.

       The solution in Elektra is flexible, because the user decides the granularity. It is
       possible to mount a backend on every single key, so that every key can be requested for
       itself. If no backends are mounted, all keys reside in the default backend.

       To sum up, Elektra's core searches for the nearest mount point and gets the configuration
       from there. It is possible that the user gets more configuration than requested. The user
       can decide by means of mounting how much configuration on specific requests are returned.