pmdalabel(3) — Linux manual page


PMDALABEL(3)            Library Functions Manual            PMDALABEL(3)

NAME         top

       pmdaLabel, pmdaSetLabelCallBack - fill pmLabelSet structures with
       metric labels

C SYNOPSIS         top

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

       int pmdaLabel(int ident, int type, pmLabelSet **sets, pmdaExt
       int pmdaSetLabelCallBack(pmdaInterface *dispatch,
               pmdaLabelCallBack callback);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION         top

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

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

           when ident is a PMDA domain identifier,

           when ident is a metric identifier and labels for the cluster
           containing that metric are being requested.

           when ident is a metric identifier,

           when ident is an instance domain identifier, or

           when ident is a metric identifier and labels for all in‐
           stances of that metric are being requested.

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

       This is one of the few generic callbacks in libpcp_pmda (see
       PMDA(3)) that is incomplete, requiring a further pmdaLabelCall‐
       Back method of its own.  The additional callback should be regis‐
       tered using pmdaSetLabelCallBack 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 la‐
       bel(s) for an individual instance inst of a given instance do‐
       main, indom.  Its successful return code differs significantly to
       pmdaLabel, as described below.

CAVEAT         top

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

DIAGNOSTICS         top

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

       By contrast, on success of the pmdaLabelCallBack routine the num‐
       ber 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.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.  In‐
       formation about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to  This page was obtained from the project's
       upstream Git repository
       ⟨⟩ on 2024-06-14.
       (At that time, the date of the most recent commit that was found
       in the repository was 2024-06-14.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                      PMDALABEL(3)

Pages that refer to this page: pmdacache(3)pmdainstance(3)