95 lines
2.7 KiB
C++
95 lines
2.7 KiB
C++
#pragma once
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#include <atomic>
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#include "prometheus/client_metric.h"
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#include "prometheus/detail/builder.h" // IWYU pragma: export
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#include "prometheus/detail/core_export.h"
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#include "prometheus/metric_type.h"
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namespace prometheus {
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/// \brief A gauge metric to represent a value that can arbitrarily go up and
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/// down.
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///
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/// The class represents the metric type gauge:
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/// https://prometheus.io/docs/concepts/metric_types/#gauge
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///
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/// Gauges are typically used for measured values like temperatures or current
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/// memory usage, but also "counts" that can go up and down, like the number of
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/// running processes.
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///
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/// The class is thread-safe. No concurrent call to any API of this type causes
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/// a data race.
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class PROMETHEUS_CPP_CORE_EXPORT Gauge {
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public:
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static const MetricType metric_type{MetricType::Gauge};
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/// \brief Create a gauge that starts at 0.
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Gauge() = default;
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/// \brief Create a gauge that starts at the given amount.
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explicit Gauge(double);
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/// \brief Increment the gauge by 1.
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void Increment();
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/// \brief Increment the gauge by the given amount.
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void Increment(double);
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/// \brief Decrement the gauge by 1.
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void Decrement();
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/// \brief Decrement the gauge by the given amount.
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void Decrement(double);
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/// \brief Set the gauge to the given value.
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void Set(double);
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/// \brief Set the gauge to the current unix time in seconds.
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void SetToCurrentTime();
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/// \brief Get the current value of the gauge.
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double Value() const;
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/// \brief Get the current value of the gauge.
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///
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/// Collect is called by the Registry when collecting metrics.
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ClientMetric Collect() const;
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private:
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void Change(double);
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std::atomic<double> value_{0.0};
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};
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/// \brief Return a builder to configure and register a Gauge metric.
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///
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/// @copydetails Family<>::Family()
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///
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/// Example usage:
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///
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/// \code
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/// auto registry = std::make_shared<Registry>();
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/// auto& gauge_family = prometheus::BuildGauge()
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/// .Name("some_name")
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/// .Help("Additional description.")
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/// .Labels({{"key", "value"}})
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/// .Register(*registry);
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///
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/// ...
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/// \endcode
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///
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/// \return An object of unspecified type T, i.e., an implementation detail
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/// except that it has the following members:
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///
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/// - Name(const std::string&) to set the metric name,
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/// - Help(const std::string&) to set an additional description.
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/// - Labels(const Labels&) to assign a set of
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/// key-value pairs (= labels) to the metric.
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///
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/// To finish the configuration of the Gauge metric register it with
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/// Register(Registry&).
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PROMETHEUS_CPP_CORE_EXPORT detail::Builder<Gauge> BuildGauge();
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} // namespace prometheus
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