NAME

       __pmLocalPMDA - change the table of DSO PMDAs for PM_CONTEXT_LOCAL contexts

C SYNOPSIS

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

       int __pmLocalPMDA(int op, int domain, const char *name, const char *init);

       cc ... -lpcp

DESCRIPTION

       PCP contexts of type PM_CONTEXT_LOCAL are used by clients that wish to fetch metrics directly from one or
       more  PMDAs on the local host without involving pmcd(1).  A PMDA that is to be used in this way must have
       been built as a Dynamic Shared Object (DSO).

       Historically the table of PMDAs available for use with PM_CONTEXT_LOCAL was hardcoded to the following:

       * The PMDA (or PMDAs) that export the operating system performance data and data about process activity.
       * The mmv PMDA.
       * The sample PMDA provided $PCP_LITE_SAMPLE or $PMDA_LOCAL_SAMPLE is set in the environment - used mostly
         for QA and testing.

       The initial table of PMDAs available for use with PM_CONTEXT_LOCAL is now generated dynamically from  all
       those  PMDAs  that have been installed as DSOs on the local host.  The one exception is the ``pmcd'' PMDA
       which only operates correctly in the address space of a running pmcd(1) process and so is  not  available
       to an application using a PM_CONTEXT_LOCAL context.

       __pmLocalPMDA  provides  a  number of services to amend the table of PMDAs available for use with PM_CON‐
       TEXT_LOCAL.

       The op argument specifies the what should be done and takes one of the following values and actions:

       PM_LOCAL_ADD    Append an entry to the table for the PMDA with a Performance Metrics Domain (PMD) of  do‐
                       main,  the path to the DSO PMDA is given by path and the PMDA's initialization routine is
                       init.

       PM_LOCAL_DEL    Removes all entries in the table where the domain matches, or the path matches.   Setting
                       the  arguments domain to -1 or path to NULL to force matching on the other argument.  The
                       init argument is ignored.

       PM_LOCAL_CLEAR  Remove all entries from the table.  All the other arguments are ignored in this case.

       The domain, name and init arguments have similar syntax and semantics to the associated fields in the pm‐
       cd(1) configuration file.  The one difference is the path argument which is used by __pmLocalPMDA to find
       a likely looking DSO by searching in this order: $PCP_PMDAS_DIR/path, path,  $PCP_PMDAS_DIR/path.dso-suf‐
       fix and finally path.dso-suffix (dso-suffix is the local platform specific default file name suffix for a
       DSO, e.g.  so for Linux, dylib for Mac OS X, dll for Windows, etc.).

RETURN VALUE

       In  most  cases, __pmLocalPMDA returns 0 to indicate success.  If op is invalid, then the return value is
       PM_ERR_CONV else if there is no matching table entry found for a PM_LOCAL_DEL operation, PM_ERR_INDOM  is
       returned.

SEE ALSO

       pmcd(1), PMAPI(3), pmNewContext(3) and __pmSpecLocalPMDA(3).

Performance Co-Pilot                                                                              PMLOCALPMDA(3)