pmdalabel(3) — Linux manual page

NAME | C SYNOPSIS | DESCRIPTION | CAVEAT | DIAGNOSTICS | SEE ALSO | COLOPHON

PMDALABEL(3)            Library Functions Manual            PMDALABEL(3)

NAME         top

       pmdaLabel, pmdaSetLabelCallBack - fill pmdaLabelSet structures
       with metric labels

C SYNOPSIS         top

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

       int pmdaLabel(int ident, int type, pmLabelSet **sets, pmdaExt
               *pmda);
       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
       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 requested.

       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 allocated 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 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
       label(s) for an individual instance inst of a given instance
       domain, indom.  Its successful return code differs significantly
       to pmdaLabel, as described below.

CAVEAT         top

       The PMDA must be using PMDA_PROTOCOL_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_INSTANCES 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
       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.

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.
       Information about the project can be found at 
       ⟨http://www.pcp.io/⟩.  If you have a bug report for this manual
       page, send it to pcp@groups.io.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/performancecopilot/pcp.git⟩ on 2021-08-27.
       (At that time, the date of the most recent commit that was found
       in the repository was 2021-08-27.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

Performance Co-Pilot               PCP                      PMDALABEL(3)

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