PMDAEVENTCLIENT(3)					     Library Functions Manual						PMDAEVENTCLIENT(3)

NAME

       pmdaEventNewClient, pmdaEventEndClient, pmdaEventClients - client context tracking interfaces for event queues

C SYNOPSIS

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

       int pmdaEventNewClient(int context);
       int pmdaEventEndClient(int context);
       int pmdaEventClients(pmAtomValue *avp);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION

       A Performance Metrics Domain Agent (PMDA) that exports event records needs to track which clients are connected to it, in order that it can
       track which events have been sent to which clients so far.  Only once an event has been sent to all monitoring tools that registered an in-
       terest can the event be discarded and any memory reclaimed.

       The PMDA(3) library provides callback routines for PMDA developers to provide custom handling of client connections and disconnections.	If
       the PMDA is making use of the event queueing mechanism provided by pmdaEventNewQueue(3) and friends, client connections and  disconnections
       must  be tracked via calls to pmdaEventNewClient and pmdaEventEndClient respectively.  This allows the library to keep track of when events
       can be discarded from a queue, for example, for the context specified.  This parameter is passed into the e_endCallBack function  directly,
       and  for  other	callback  functions is available via the e_context field of the pmdaExt structure.  Additionally, it can be queried at any
       time using pmdaGetContext(3).

       Sometimes it is useful for the PMDA to export a metric indicating the current count of attached clients - this is available using  the  pm-
       daEventClients routine, which will fill in the avp pmAtomValue structure on behalf of a PMDA fetch callback routine.

SEE ALSO

       pmdaEventNewArray(3), pmdaEventNewQueue(3), PMAPI(3), PMDA(3) and pmEventFlagsStr(3).

Performance Co-Pilot							PCP							PMDAEVENTCLIENT(3)