pmdachildren(3)

NAME

   pmdaChildren  - translate a PMID to a set of dynamic performance metric
   names

C SYNOPSIS

   #include <pcp/pmapi.h>
   #include <pcp/impl.h>
   #include <pcp/pmda.h>

   int pmdaChildren(char *name, int traverse, char ***offspring,
           int **status, pmdaExt *pmda);

   cc ... -lpcp_pmda -lpcp

DESCRIPTION

   As  part  of  the  Performance  Metrics  Domain  Agent  (PMDA) API (see
   PMDA(3)), pmdaChildren is the generic callback  for  returning  dynamic
   metric names (and their status) that are descendants of name.

   Because implementing dynamic performance metrics requires specific PMDA
   support, and the facility is an optional  component  of  a  PMDA  (most
   PMDAs  do  not  support dynamic performance metrics), pmdaChildren is a
   skeleton implementation that returns PM_ERR_NAME.

   A PMDA that supports dynamic performance metrics will provide a private
   callback    that    replaces    pmdaChildren    (by    assignment    to
   version.four.children of the pmdaInterface  structure)  and  takes  the
   initial  metric  name and returns names via offspring[] and the leaf or
   non-leaf status of each via status[].

   If traverse is 0, then the behaviour is akin  to  pmGetChildren(3)  and
   offspring[]  contains  the  relative  name  component for the immediate
   descendants of name.

   If traverse is 1, then the behaviour is akin to  pmTraversePMNS(3)  and
   offspring[] contains the absolute names of all dynamic metrics that are
   decedents of name.

   The resulting list of pointers offspring and  the  values  (the  names)
   that  the  pointers  reference will have been allocated by pmdaChildren
   with a single call to malloc(3), and the caller  of  pmdaChildren  will
   call  free(offspring)  to  release  the  space  when  it  is  no longer
   required.  The same holds true for the status array.

DIAGNOSTICS

   pmdaChildren returns PM_ERR_NAME if  the  name  is  not  recognized  or
   cannot  be  translated, otherwise the number of descendent metric names
   found.

CAVEAT

   The PMDA must be using PMDA_PROTOCOL_4 or later, as  specified  in  the
   call to pmdaDSO(3) or pmdaDaemon(3).

SEE ALSO

   PMAPI(3),     PMDA(3),    pmdaDaemon(3),    pmdaDSO(3),    pmdaMain(3),
   pmGetChildren(3) and pmTraversePMNS(3).

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