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_CONTEXT_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 domain, 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 pmcd(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-suffix  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).