Telemetry#

Macros for Sensing Metrics#

The following macros should be used for triggering sending metrics manually.

Defines

STAT(name, value)#

Trigger a metric to be sent with a given value. The value expression is only evaluated if sending should take place.

Parameters:

  • name – Name of the metric

  • value – Value or function returning the value of the metric

STAT_IF(name, value, condition)#

Trigger a metric to be sent with a given value if the given condition is met. The given condition is evaluated after it was evaluated if sending should take place.

Parameters:

  • name – Name of the metric

  • value – Value or function returning the value of the metric

  • condition – Expression returning a bool if the metric should be triggered

STAT_NTH(name, value, count)#

Trigger a metric to be sent every nth call.

Parameters:

  • name – Name of the metric

  • value – Value or function returning the value of the metric

  • count – Interval of calls at which the metric should be triggered

STAT_T(name, value, interval)#

Trigger a metric to be sent at most every t seconds.

Parameters:

  • name – Name of the metric

  • value – Value or function returning the value of the metric

  • interval – Time interval at which the metric should be triggered

Note

The value within the STAT macros can be a function. This way the function retrieving the value is only executed when the conditions are met and there is at least one subscriber for the metric.

constellation::metrics Namespace#

enum class constellation::metrics::MetricType : std::uint8_t#

Metrics types

Values:

enumerator LAST_VALUE#

Always keep the latest value, replace earlier ones

enumerator ACCUMULATE#

Sum every new value to previously received ones

enumerator AVERAGE#

Calculate the average value

enumerator RATE#

Calculate the rate from the value over a given time interval

class InvalidMetricValueException : public constellation::utils::LogicError#
#include <constellation/core/metrics/exceptions.hpp>

Value of a metric has an invalid type.

Public Functions

inline explicit InvalidMetricValueException(std::string_view name, std::string_view type)#
class Metric#
#include <constellation/core/metrics/Metric.hpp>

This class represents a metric for telemetry or data quality monitoring.

It comprises a name, a unit and a type. The type defines how the value should be treated, i.e. if always the last transmitted value should be displayed, if an average of the values should be calculated or if they should be accumulated.

Subclassed by constellation::metrics::TimedMetric

Public Functions

inline Metric(std::string name, std::string unit, MetricType type)#

Metric constructor.

Parameters:

  • name – Name of the metric

  • unit – Unit of the metric as human readable string

  • type – Type of the metric

inline std::string_view name() const#

Obtain the name of the metrics.

Returns:

Name of the metric

inline std::string_view unit() const#

Obtain unit as human-readable string.

Returns:

Unit of the metric

inline MetricType type() const#

Obtain type of the metric.

Returns:

Metric type

class MetricsManager#
#include <constellation/core/metrics/MetricsManager.hpp>

Manager for Metrics handling & transmission

Public Functions

virtual ~MetricsManager() noexcept#
void registerMetric(std::shared_ptr<Metric> metric)#

Register a (manually triggered) metric

Parameters:

metric – Shared pointer to the metric

void registerMetric(std::string name, std::string unit, metrics::MetricType type)#

Register a (manually triggered) metric

Parameters:

  • name – Unique topic of the metric

  • unit – Unit of the provided value

  • type – Type of the metric

void registerTimedMetric(std::shared_ptr<TimedMetric> metric)#

Register a timed metric

Parameters:

metric – Shared pointer to the timed metric

template<typename C>
void registerTimedMetric(std::string name, std::string unit, metrics::MetricType type, std::chrono::steady_clock::duration interval, C value_callback)#

Register a timed metric

Parameters:

  • name – Name of the metric

  • unit – Unit of the metric as human readable string

  • type – Type of the metric

  • interval – Interval in which to send the metric

  • value_callback – Callback to determine the current value of the metric

void unregisterMetric(std::string_view name)#

Unregister a previously registered metric from the manager

Parameters:

name – Name of the metric

void unregisterMetrics()#

Unregisters all metrics registered in the manager

Equivalent to calling unregisterMetric for every registered metric.

void triggerMetric(std::string name, config::Value value)#

Manually trigger a metric

Parameters:

  • name – Name of the metric

  • value – Value of the metric

Public Static Functions

static MetricsManager &getInstance()#

Return instance of metrics manager.

static inline bool shouldStat(std::string_view)#

Check if a metric should be send given the subscription status

class MetricValue#
#include <constellation/core/metrics/Metric.hpp>

Class containing a pointer to a metric and a corresponding metric value.

Public Functions

inline MetricValue(std::shared_ptr<Metric> metric, config::Value &&value)#

Metric value constructor.

Parameters:

  • metric – Shared pointer to a metric

  • value – Value corresponding to the metric

MetricValue() = default#
inline std::shared_ptr<Metric> getMetric() const#

Obtain the underlying metric.

Returns:

Shared pointer tot the metric

inline const config::Value &getValue() const#

Obtain the metric value.

Returns:

Value of the metric

message::PayloadBuffer assemble() const#

Assemble metric via msgpack for message payload

Public Static Functions

static MetricValue disassemble(std::string name, const message::PayloadBuffer &message)#

Disassemble metric from message payload

class TimedMetric : public constellation::metrics::Metric#
#include <constellation/core/metrics/Metric.hpp>

This class represents a timed metric for telemetry or data quality monitoring.

A timed metric is a metric that is polled in regular intervals. It requires an interval, a value callback, and a list of states where the callback is allowed to be called.

Public Functions

inline TimedMetric(std::string name, std::string unit, MetricType type, std::chrono::nanoseconds interval, std::function<std::optional<config::Value>()> value_callback)#

Timed metric constructor.

Parameters:

  • name – Name of the metric

  • unit – Unit of the metric as human readable string

  • type – Type of the metric

  • interval – Interval in which to send the metric

  • value_callback – Callback to determine the current value of the metric

inline std::chrono::nanoseconds interval() const#

Obtain interval of the metric.

Returns:

Interval in nanoseconds

inline std::optional<config::Value> currentValue()#

Evaluate the value callback to get the current value of the metric.

Returns:

Optional with current value or no value