введение в библиотеку поддержки агента домена Performance Metrics (introduction to the Performance Metrics Domain Agent support library)
DAEMON PMDA
A PMDA that is run as a daemon is forked and executed by pmcd(1).
Therefore, unlike a DSO PMDA, the starting point for a daemon
PMDA is main(). The agent should parse the command line
arguments, create a log file and initialize some data structures
that pmcd(1) would initialize for a DSO agent.
The pmdaInterface structure must be completely defined by the
daemon PMDA. The function pmdaDaemon(3) can be called at the
start of main() to set most of these fields. Command line
parsing can be simplified by using pmdaGetOpt(3), which is
similar to getopt(2), but extracts a common set of options into
the pmdaInterface structure. stderr can be mapped to a log file
using pmdaOpenLog(3) to simplify debugging and error messages.
The connection to pmcd(1) can be made with pmdaConnect(3) and the
loop which handles the incoming PDUs, pmdaMain(3), should be the
last function called. This can be seen in
$PCP_PMDAS_DIR/simple/simple.c.
The simple_init() routine is common to an agent that can be run
as both a Daemon and DSO PMDA.
