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#pragma once
#include "prometheus/client_metric.h"
#include "prometheus/detail/builder.h" // IWYU pragma: export
#include "prometheus/detail/core_export.h"
#include "prometheus/gauge.h"
#include "prometheus/metric_type.h"
namespace prometheus {
/// \brief A counter metric to represent a monotonically increasing value.
///
/// This class represents the metric type counter:
/// https://prometheus.io/docs/concepts/metric_types/#counter
///
/// The value of the counter can only increase. Example of counters are:
/// - the number of requests served
/// - tasks completed
/// - errors
///
/// Do not use a counter to expose a value that can decrease - instead use a
/// Gauge.
///
/// The class is thread-safe. No concurrent call to any API of this type causes
/// a data race.
class PROMETHEUS_CPP_CORE_EXPORT Counter {
public:
static const MetricType metric_type{MetricType::Counter};
/// \brief Create a counter that starts at 0.
Counter() = default;
/// \brief Increment the counter by 1.
void Increment();
/// \brief Increment the counter by a given amount.
///
/// The counter will not change if the given amount is negative.
void Increment(double);
/// \brief Get the current value of the counter.
double Value() const;
/// \brief Get the current value of the counter.
///
/// Collect is called by the Registry when collecting metrics.
ClientMetric Collect() const;
private:
Gauge gauge_{0.0};
};
/// \brief Return a builder to configure and register a Counter metric.
///
/// @copydetails Family<>::Family()
///
/// Example usage:
///
/// \code
/// auto registry = std::make_shared<Registry>();
/// auto& counter_family = prometheus::BuildCounter()
/// .Name("some_name")
/// .Help("Additional description.")
/// .Labels({{"key", "value"}})
/// .Register(*registry);
///
/// ...
/// \endcode
///
/// \return An object of unspecified type T, i.e., an implementation detail
/// except that it has the following members:
///
/// - Name(const std::string&) to set the metric name,
/// - Help(const std::string&) to set an additional description.
/// - Labels(const Labels&) to assign a set of
/// key-value pairs (= labels) to the metric.
///
/// To finish the configuration of the Counter metric, register it with
/// Register(Registry&).
PROMETHEUS_CPP_CORE_EXPORT detail::Builder<Counter> BuildCounter();
} // namespace prometheus
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