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NAME | C SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON |
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PMDAEVENTCLIENT(3) Library Functions Manual PMDAEVENTCLIENT(3)
pmdaEventNewClient, pmdaEventEndClient, pmdaEventClients - client
context tracking interfaces for event queues
#include <pcp/pmapi.h>
#include <pcp/pmda.h>
int pmdaEventNewClient(int context);
int pmdaEventEndClient(int context);
int pmdaEventClients(pmAtomValue *avp);
cc ... -lpcp_pmda -lpcp
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.
pmdaEventNewArray(3), pmdaEventNewQueue(3), PMAPI(3), PMDA(3) and
pmEventFlagsStr(3).
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation 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 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-14.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
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 PMDAEVENTCLIENT(3)
Pages that refer to this page: pmdaeventarray(3), pmdaeventqueue(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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