QMC_GROUP(3)

NAME
QmcGroup - container representing a single fetch group of metrics from multiple sources

C++ SYNOPSIS
#include <QmcGroup.h>

CC ... -lqmc -lpcp

DESCRIPTION
A QmcGroup object is a container for contexts and metrics that should be fetched at the same time. The class manages the QmcContext(3) objects, timezones and bounds for every context created with QmcGroup::use and QmcGroup::addMetric.

CONSTRUCTORS & DESTRUCTOR

~QmcGroup();
    Destructor which destroys all metrics and contexts created by this group.

QmcGroup(bool restrictArchives = false);
    Construct a new fetch group. restrictArchives will restrict the creating of multiple archive contexts created from the same host.

CONTEXTS
The default context of the group is defined as the first context created with QmcGroup::use before the first call to QmcGroup::addMetric. If no context is created before the first metric is added, the localhost is used as the default context. Therefore, if any metrics specifications contain archive sources, an archive source must have been created with QmcGroup::use to avoid an error for mixing context types.

uint_t numContexts() const;
    The number of valid contexts created in this group.

QmcContext const& context(uint_t index) const
    Return a handle to a context.

QmcContext& context(uint_t index);
    Return a modifiable handle to a context.

int mode() const;
    Return the type of context, either PM_CONTEXT_LOCAL, PM_CONTEXT_HOST or PM_CONTEXT_ARCHIVE.

QmcContext* which() const;
    Return a handle to the current context of this group. This does not call pmUseContext(3) so it may not be the current PMAPI(3) context.

uint_t whichIndex() const
    The index to the current group context.

int use(int type, char const* source);
    Use the context of type from source. If a context to this source already exists in this group, that context will become the current PMAPI(3) context. Otherwise a new context will be created. The result is the PMAPI(3) context handle for the QmcGroup::context or a PMAPI(3) error code if the context failed.

bool defaultDefined() const;
    Returns true if a default context has been determined.

int useDefault();
    Use the default context. If a default context has not been created, the context to the local host will be attempted. A result less than zero indicates that the method failed with the PMAPI(3) error encoded in the result.

void createLocalContext();
    Create and use a context to the local host. A result less than zero indicates that the method failed with the PMAPI(3) error encoded in the result.

METRICS
These addMetric methods should be used to create new metrics as the QmcMetric constructors are private. These methods will always return a pointer to a QmcMetric object, however the QmcMetric::status() field should be checked to ensure the metric is valid.

QmcMetric* addMetric(char const* str, double theScale = 0.0,
    bool active = false); Add the metric str to the group, with a scaling factor of scale. If active is set the metric will use only active instances (see QmcMetric(3)).

QmcMetric* addMetric(pmMetricSpec* theMetric, double theScale
    = 0.0, bool active); Add the metric theMetric to the group, with a scaling factor of scale. If active is set the metric will use only active instances (see QmcMetric(3)).

int fetch(bool update = true);
    Fetch all the metrics in all the contexts in this group. If update is equal to true, all counter metrics will be automatically converted to rates (see QmcMetric(3)).

int setArchiveMode(int mode, const struct timeval *when,
    int interval); Set the mode and time to access all archive contexts in this group. See pmSetmode(3) for more details.

TIMEZONES
These methods assist in the management of multiple timezones and help to control the current timezone.

enum TimeZoneFlag { localTZ, userTZ, groupTZ, unknownTZ };
    Enumeration used to describe the origin of the default timezone. localTZ, userTZ and groupTZ indicate that the timezone was set with QmcGroup::useLocalTZ, QmcGroup::useTZ(QString const&) and QmcGroup::useTZ() respectively. unknownTZ indicates that a timezone has not been set. userTZ indicates that the timezone was

int useTZ();
    Use the timezone of the current group context as the default.

int useTZ(const QString &tz);
    Add and use tz as the default timezone of this group.

int useLocalTZ();
    Use the timezone of the localhost as the default for this group.

void defaultTZ(QString &label, QString &tz);
    Return the label and tz string of the default timezone of this group.

TimeZoneFlag defaultTZ() const
    Return the origin of the default timezone.

int useDefaultTZ();
    Set the timezone to be the default timezone as defined in a previous call to QmcGroup::useTZ or QmcGroup::useLocalTZ.

struct timeval const& logStart() const;
    Return the earliest starting time of any archives in this group. Assumes that QmcGroup::updateBounds has been called.

struct timeval const& logEnd() const;
    Return the latest finish time of any archives in this group. Assumes that QmcGroup::updateBounds has been called.

void updateBounds();
    Determine the earliest start and latest finish times of all archives in this group.

int sendTimezones();
    Send the current timezones to kmtime (3).

DEBUGGING

void dump(ostream &os);
    Dump state information about this group to os.

SEE ALSO
PMAPI(3), QMC(3), QmcContext(3), QmcMetric(3), pmflush(3), pmprintf(3) and pmSetMode(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.