QMC_METRIC(3)

NAME
QmcMetric - container for a metric and all its values

C++ SYNOPSIS
#include <pcp/pmc/Metric.h>

CC ... -lpcp_pmc -lpcp

DESCRIPTION
A QmcMetric object is a container for a single metric and all its values.

The QmcMetricValue structure is used to hold the instance index, values and errors of each instance. In the case of a singular metric, a single QmcMetricValue object is used.

A QmcMetric object consists of a list of QmcMetricValue objects, indexes to the descriptors in the metric's QmcGroup and QmcContext and flags to indicate if the instances are explicit or implicit, and if only active metrics are required after QmcMetric::updateIndom is called.

CONSTRUCTORS
Metrics should be constructed through the QmcGroup::addMetric methods as this will ensure that the references to the metric's context, descriptor and instance domain are correctly initialized.

INSTANCES
For metrics with an instance domain it is possible to add and remove any instance, and also update the instance list to reflect changes in a dynamic instance domain.

bool updateIndom();
    Update the metric to include new instances. This method will first call QmcContext::update to update the instance domain. If the active flag is set in the QmcGroup::addMetric call, only instances will exported by the metric, otherwise the metric will export all instances listed in the domain.

    The ordering of instances may change as a result of this call. Instances that already existed will keep their current and previous values and errors, even if they are in a different order.

int addInst(QString const& name);
    Add the instance name to the metric. If the instance does not exist in the instance domain, a PMAPI(3) error will be returned. This method ignores the value of the active flag set in the QmcMetric constructor.

void removeInst(uint_t index);
    Remove the instance at position index from the metric.

SEE ALSO
PMAPI(3), QMC(3), QMC_Context(3), QMC_Group(3), pmflush(3) and pmprintf(3).

DIAGNOSTICS
Error messages are generated using pmprintf(3) but are not flushed. It is the responsibility of the user to call pmflush(3) to output any messages.

Additional diagnostics may be activated by adding DBG_TRACE_PMC to the global pmDebug.