pmdaLabel, pmdaSetLabelCallBack - fill pmLabelSet structures with metric labels

#include<pcp/pmapi.h>#include<pcp/pmda.h>intpmdaLabel(intident,inttype,pmLabelSet**sets,pmdaExt*pmda);intpmdaSetLabelCallBack(pmdaInterface*dispatch,pmdaLabelCallBackcallback);cc...-lpcp_pmda-lpcp

       The  PMDA  must  be  using  PMDA_INTERFACE_7 or later, as specified in the call to pmdaDSO(3) or pmdaDae‐mon(3).

       As part of the Performance Metrics Domain Agent (PMDA) API (see PMDA(3)), pmdaLabel uses the standard PM‐DA(3)  data structures to return the labels for performance domain, instance domain, metric or individual
       instances in "JSONB" format in the given sets data structure.

       The type argument determines the interpretation of ident and the requested form of label, as follows:

       PM_LABEL_DOMAIN
           when ident is a PMDA domain identifier,

       PM_LABEL_CLUSTER
           when ident is a metric identifier and labels for the cluster containing that  metric  are  being  re‐
           quested.

       PM_LABEL_ITEM
           when ident is a metric identifier,

       PM_LABEL_INDOM
           when ident is an instance domain identifier, or

       PM_LABEL_INSTANCES
           when ident is a metric identifier and labels for all instances of that metric are being requested.

       The label sets pointer must be initialised to NULL before calling pmdaLabel and space is only to be allo‐
       cated  when  labels  are present and returned.  In this case, the return code must indicate the number of
       label sets that have been allocated.  This will only ever be greater than one in  the  PM_LABEL_INSTANCES
       case.

       This  is  one  of  the few generic callbacks in libpcp_pmda (see PMDA(3)) that is incomplete, requiring a
       further pmdaLabelCallBack method of its own.  The additional callback should be registered using pmdaSet‐LabelCallBack and the pmdaLabelCallBack method has the following prototype:
       int func(pmInDom indom, unsigned int inst, pmLabelSet **set)

       The purpose of the pmdaLabelCallBack routine is to return the label(s) for an individual instance inst of
       a given instance domain, indom.  Its successful return code differs significantly to  pmdaLabel,  as  de‐
       scribed below.

       On success pmdaLabel returns the number of label sets created.  This is usually zero or  one,  except  in
       the  case  of  PM_LABEL_INSTANCES where more than one label sets will often be returned, one for each in‐
       stance of the requested metric.

       By contrast, on success of the pmdaLabelCallBack routine the number of labels successfully added  to  the
       provided labelset pointer must be returned (and not the total number of label sets).

       If labels for the requested entity could not be obtained due to a catastrophic failure, such as an out of
       memory condition, these routines will return a negative error code.

pmdaLabel, pmdaSetLabelCallBack - fill pmLabelSet structures with metric labels

pminfo(1), malloc(3), PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3), pmdaInit(3) and pmLookupLabels(3).

Performance Co-Pilot                                   PCP                                          PMDALABEL(3)