клиентские интерфейсы отслеживания контекста для очередей событий (client context tracking interfaces for event queues)
Имя (Name)
pmdaEventNewClient, pmdaEventEndClient, pmdaEventClients - client
context tracking interfaces for event queues
Синопсис C (C Synopsis)
#include <pcp/pmapi.h>
#include <pcp/pmda.h>
int pmdaEventNewClient(int context);
int pmdaEventEndClient(int context);
int pmdaEventClients(pmAtomValue *avp);
cc ... -lpcp_pmda -lpcp
Описание (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 interest 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 pmdaEventClients routine, which will fill in the avp
pmAtomValue structure on behalf of a PMDA fetch callback routine.
Смотри также (See also)
pmdaEventNewArray(3), pmdaEventNewQueue(3), PMAPI(3), PMDA(3) and
pmEventFlagsStr(3).
