введение в библиотеку поддержки агента домена Performance Metrics (introduction to the Performance Metrics Domain Agent support library)
METRIC DESCRIPTIONS
Each metric requires a description (pmDesc), which contains its
Performance Metric Identifier (PMID), data type specification,
instance domain, semantics and units (see pmLookupDesc(3)). A
handle is also provided for application specific information in
the pmdaMetric structure:
/*
* Metric description: handle for extending description,
* and the description.
*/
typedef struct {
void* m_user; /* for users external use */
pmDesc m_desc; /* metric description */
} pmdaMetric;
The simple PMDA defines the metrics as:
static pmdaMetric metrictab[] = {
/* numfetch */
{ (void *)0,
{ PMDA_PMID(0,0), PM_TYPE_U32, PM_INDOM_NULL, PM_SEM_INSTANT,
{ 0,0,0,0,0,0} }, },
/* color */
{ (void *)0,
{ PMDA_PMID(0,1), PM_TYPE_32, COLOR_INDOM, PM_SEM_INSTANT,
{ 0,0,0,0,0,0} }, },
/* time.user */
{ (void*)0,
{ PMDA_PMID(1,2), PM_TYPE_DOUBLE, PM_INDOM_NULL, PM_SEM_COUNTER,
{ 0, 1, 0, 0, PM_TIME_SEC, 0 } }, },
/* time.sys */
{ (void*)0,
{ PMDA_PMID(1,3), PM_TYPE_DOUBLE, PM_INDOM_NULL, PM_SEM_COUNTER,
{ 0, 1, 0, 0, PM_TIME_SEC, 0 } }, },
/* now */
{ NULL,
{ PMDA_PMID(2,4), PM_TYPE_U32, NOW_INDOM, PM_SEM_INSTANT,
{ 0,0,0,0,0,0 } }, },
};
The macro PMDA_PMID (defined in /usr/include/pcp/pmda.h) is used
to specify each metric's cluster and item fields of the
associated pmID. As with instance domains, the domain field is
set by pmdaInit(3) at run-time, however, the default domain is
assumed to be defined by the PMDA in the macro MYDOMAIN.
The metric table shown above which is usually passed to
pmdaInit(3) does not need to be created if one wants to write
one's own Fetch and Descriptor functions. See pmdaInit(3) for
more details.
