NAME
pmStore, pmRequestStore, pmReceiveStore - modify values of performance
metrics
C SYNOPSIS
#include <pcp/pmapi.h>
int pmStore(const pmResult *result)
int pmRequestStore(int ctx, const pmResult *result)
int pmReceiveStore(int ctx)
cc ... -lpcp
DESCRIPTION
In some special cases it may be helpful to modify the current values of
performance metrics, e.g. to reset a counter to zero, or to modify a
‘‘metric’’ which is a control variable for some agent collecting
performance metrics.
The routine pmStore is a lightweight inverse of pmFetch(3).
The caller must build the pmResult data structure (of course, this
could have been returned from an earlier pmFetch(3) call) and then call
pmStore.
It is an error to pass a request to pmStore in which the numval field
within any of the pmValueSet structure has a value less than one.
The current Performance Metrics Application Programming Interface
(PMAPI) context must be one with a host as the source of metrics, and
the current value of the nominated metrics will be changed, i.e.
pmStore cannot be used to make retrospective changes to information in
either the archive logs, or in the recent past for real-time sources of
metrics.
The return code from pmStore is zero for success.
pmRequestStore and pmReceiveStore are used by applications which must
communicate with the PMCD asynchronously. These functions take explict
context handle ctx which must refer to a host context (i.e. created by
passing PM_CONTEXT_HOST to pmNewContext). pmRequestStore sends request
to store data in result in the metrics and returns without waiting for
the response, pmReceiveStore reads confirmation from PMCD. It is the
responsibility of the application to make sure the data are ready
before calling pmReceiveStore to avoid blocking.
SEE ALSO
PMAPI(3), pmFetch(3) and pmSetMode(3).
DIAGNOSTICS
PM_ERR_GENERIC
At least one of the modifications was rejected. No other status
is available from below the PMAPI (this is the lightweight part
of the functionality!). In cases where the outcome of pmStore
for individual metrics is important, the caller should make one
call to pmStore for each metric. On the other hand, a bulk
modification can be performed in a single pmStore call for
situations in which the outcome is not critical.
PM_ERR_NOTHOST
The current PMAPI context is an archive rather than a host, or
it is a host that is not set to the current time, i.e. has been
‘‘rewound’’ to the recent past using pmSetMode(3).
PM_ERR_TOOSMALL
The number of metrics specified in result is less than one.
PM_ERR_VALUE
One or more of the pmValueSets in result has a numval field with
a value less than one.
PM_ERR_CTXBUSY
Context is currently in use by another asynchronous call.