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.

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.