pmdaeventclient(3) — Linux manual page

NAME | C SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON

PMDAEVENTCLIENT(3)      Library Functions Manual      PMDAEVENTCLIENT(3)

NAME         top

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

C SYNOPSIS         top

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

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

       cc ... -lpcp_pmda -lpcp

DESCRIPTION         top

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

       The  PMDA(3) library provides callback routines for PMDA develop‐
       ers to provide custom handling of client connections and  discon‐
       nections.   If the PMDA is making use of the event queuing mecha‐
       nism provided by pmdaEventNewQueue(3) and friends, client connec‐
       tions and disconnections must be tracked via calls to  pmdaEvent‐
       NewClient  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  pmdaEventClients routine, which will fill in the avp pmAtom‐
       Value structure on behalf of a PMDA fetch callback routine.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.  In‐
       formation about the project can be found at ⟨http://www.pcp.io/⟩.
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Performance Co-Pilot               PCP                PMDAEVENTCLIENT(3)

Pages that refer to this page: pmdaeventarray(3)pmdaeventqueue(3)