Namespaces
namespace	detail
	Portable atomic `shared_ptr<const T>` exposing just `load()`/`store()`.

namespace	prometheus_cpp

Classes
class	Adapter
	The pluggable backend. More...

class	AdapterCell
	A swappable adapter slot shared by every metric that reads from it. More...

class	AdapterSource
	The source a metric reads its current adapter from, decoupled from `Registry` so that `metric_base` can resolve a binding without depending on the registry layer (which would be an include cycle), mirroring `ScopeState`. More...

class	CompositeAdapter
	A backend that forwards every call to a fixed set of child adapters. More...

class	CompositeState
	Backend state for a composite family or child: the index-aligned bundle of the handles each wrapped adapter returned. More...

class	Counter
	A counter. More...

struct	CounterSpec
	Declarative description of a counter, for `Registry::counter` / `Counter::Counter`. More...

struct	Error
	A validation failure: a machine code plus a human message. More...

class	Exception
	Thrown by the throwing `Registry` factories when a spec fails validation. More...

class	Gauge
	A gauge. More...

struct	GaugeSpec
	Declarative description of a gauge. More...

class	Histogram
	A histogram. More...

struct	HistogramSpec
	Declarative description of a histogram. More...

class	Info
	An info metric: a single sample whose labels carry the payload (build version, commit, ...). More...

struct	InfoSpec
	Declarative description of an info metric. More...

struct	Label
	A single `name="value"` label pair. More...

class	Labels
	An immutable-by-convention set of labels, kept sorted by name with duplicates collapsed last-wins. More...

class	MetricBase
	CRTP base shared by every metric type. More...

struct	MetricCore
	Shared, reference-counted state behind every metric handle. More...

struct	MetricInfo
	A read-only snapshot describing one registered metric, returned by the enumeration APIs (`Registry::metrics`, `Scope::metrics`). More...

struct	MetricMeta
	The complete, backend-agnostic description of a metric family handed to `Adapter::register_metric`. More...

class	MetricState
	Opaque backend state for a registered family or a labeled child. More...

struct	NormalizedValue
	A plain magnitude paired with the unit it was carrying (empty for raw arithmetic). More...

class	NullAdapter
	A backend that records nothing. More...

class	Registry
	Creates registered metrics against a single adapter cell. More...

struct	RegistryConfig
	The decoration a `Registry` applies to every metric created through it: a name prefix, default constant labels, and default display metadata. More...

class	Scope
	A named, reconfigurable metrics instance for one library. More...

struct	ScopeConfig
	The configuration a `Scope` applies to every metric created through it. More...

class	ScopeState
	Read-only view a scoped metric uses to re-resolve its name, constant labels, and display metadata against the live scope configuration on every use. More...

class	StateSet
	A state set: each declared state is a boolean, exposed as one series per state with value 0 or 1. More...

struct	StateSetSpec
	Declarative description of a state set. More...

class	Summary
	A summary. Like a histogram but tracks quantiles instead of fixed buckets. More...

struct	SummarySpec
	Declarative description of a summary. More...

struct	Unit
	OpenMetrics unit suffix plus optional dimensional metadata. More...

class	Untyped
	An untyped metric: just a settable value. More...

struct	UntypedSpec
	Declarative description of an untyped metric. More...

Concepts
concept	DimensionalValue
	Satisfied by a dimval-like value: it exposes a `value_t`, reports its magnitude through `numeric_as_double()`, and carries unit metadata through either `unit_descriptor()` (measures) or `descriptor()` (units).

Typedefs
template<class T >
using	expected = std::expected< T, Error >
	`std::expected<T, Error>` — the result type of the `Registry::try_*` family.

using	MetricHandle = std::shared_ptr< MetricState >
	Opaque, backend-owned handle to a registered metric family or a labeled child series.

using	AdapterPtr = std::shared_ptr< Adapter >
	Shared ownership of an `Adapter`.

Enumerations
enum class	ErrorCode : std::uint8_t { InvalidMetricName , InvalidLabelName , EmptyHelp , InvalidBuckets , InvalidQuantiles , EmptyStateSet , RegistrationFailed }
	Why a metric definition or registration was rejected. More...

enum class	MetricType : std::uint8_t { Counter , Gauge , Histogram , Summary , Untyped , Info , StateSet }
	The OpenMetrics / Prometheus metric kinds prom understands. More...

Functions
template<DimensionalValue V>
NormalizedValue	normalize (const V &value)
	Reduce a dimval value to a `NormalizedValue`.

template<class T > requires std::is_arithmetic_v<T>
NormalizedValue	normalize (T value) noexcept
	Pass an arithmetic sample straight through with no unit attached.

constexpr std::string_view	to_string (const ErrorCode code) noexcept
	Human-readable spelling of an `ErrorCode`.

constexpr bool	is_valid_metric_name (std::string_view name) noexcept
	A metric name is valid when it matches Prometheus's `[a-zA-Z_][a-zA-Z0-9_]*`.

constexpr bool	is_valid_label_name (const std::string_view name) noexcept
	A label name follows the metric-name charset but additionally rejects the `__` prefix, which OpenMetrics reserves for internal use.

MetricInfo	describe (const MetricCore &core)
	Build a `MetricInfo` from a core, applying scope decoration for a scoped metric's effective name and constant labels.

Counter	counter (const CounterSpec &spec)

Gauge	gauge (const GaugeSpec &spec)

Histogram	histogram (const HistogramSpec &spec)

Summary	summary (const SummarySpec &spec)

Untyped	untyped (const UntypedSpec &spec)

Info	info (const InfoSpec &spec)

StateSet	stateset (const StateSetSpec &spec)

expected< Counter >	try_counter (const CounterSpec &spec) noexcept

expected< Gauge >	try_gauge (const GaugeSpec &spec) noexcept

expected< Histogram >	try_histogram (const HistogramSpec &spec) noexcept

expected< Summary >	try_summary (const SummarySpec &spec) noexcept

expected< Untyped >	try_untyped (const UntypedSpec &spec) noexcept

expected< Info >	try_info (const InfoSpec &spec) noexcept

expected< StateSet >	try_stateset (const StateSetSpec &spec) noexcept

std::shared_ptr< Scope >	scope (const std::string_view name, ScopeConfig config)
	Get-or-create the process-wide scope named `name`, using `config` only if it does not yet exist (a later call returns the existing scope and ignores `config` — reconfigure through the returned scope's setters instead).

std::shared_ptr< Scope >	scope (const std::string_view name)
	Get-or-create the scope named `name` with a default config whose prefix is `name + "_"`.

std::shared_ptr< Scope >	find_scope (const std::string_view name)
	Return the scope named `name`, or `nullptr` if none has been created.

std::vector< std::shared_ptr< Scope > >	scopes ()
	Every process-wide scope created so far (unordered).

std::vector< std::string >	scope_names ()
	The names of every process-wide scope created so far (unordered).

constexpr std::string_view	to_string (const MetricType type) noexcept
	Lower-case OpenMetrics spelling of a `MetricType` (e.g. `"counter"`).

Variables
constexpr std::array< double, 11 >	default_histogram_buckets
	The default bucket bounds applied when a histogram spec leaves `buckets` empty — the canonical Prometheus client default set (seconds-oriented).

constexpr std::array< double, 3 >	default_summary_quantiles = {0.5, 0.9, 0.99}
	Default quantiles applied when a summary spec leaves `quantiles` empty.

Typedef Documentation

◆ AdapterPtr

using prom::AdapterPtr = typedef std::shared_ptr<Adapter>

Shared ownership of an Adapter.

The process-wide default and every Registry hold one of these.

◆ expected

template<class T >

using prom::expected = typedef std::expected<T, Error>

std::expected<T, Error> — the result type of the Registry::try_* family.

◆ MetricHandle

using prom::MetricHandle = typedef std::shared_ptr<MetricState>

Opaque, backend-owned handle to a registered metric family or a labeled child series.

Always non-null once handed back by an Adapter.

Enumeration Type Documentation

◆ ErrorCode

enum class prom::ErrorCode : std::uint8_t

strong

Why a metric definition or registration was rejected.

Enumerator
InvalidMetricName	Name violates `[a-zA-Z_][a-zA-Z0-9_]*`.
InvalidLabelName	A label name is invalid or uses the reserved `__` prefix.
EmptyHelp	Help text is required but was empty.
InvalidBuckets	Histogram buckets are unsorted, empty, or non-finite.
InvalidQuantiles	Summary quantiles fall outside the open interval (0, 1).
EmptyStateSet	A state set was declared with no states.
RegistrationFailed	The backend refused to register the metric.

◆ MetricType

enum class prom::MetricType : std::uint8_t

strong

The OpenMetrics / Prometheus metric kinds prom understands.

The numeric values are stable and intended for cheap switch dispatch inside adapters; do not rely on them crossing an ABI boundary.

Enumerator
Counter	Monotonically increasing cumulative value.
Gauge	Value that can go up and down.
Histogram	Bucketed distribution of observations.
Summary	Quantile summary of observations.
Untyped	A bare value with no semantic constraints.
Info	Static key/value metadata (exposed as `*_info`).
StateSet	A set of mutually-related boolean states.

Function Documentation

◆ counter()

Counter prom::counter ( const CounterSpec & spec )

inline

◆ describe()

MetricInfo prom::describe ( const MetricCore & core )

inline

Build a MetricInfo from a core, applying scope decoration for a scoped metric's effective name and constant labels.

◆ find_scope()

std::shared_ptr< Scope > prom::find_scope ( const std::string_view name )

inline

Return the scope named name, or nullptr if none has been created.

◆ gauge()

Gauge prom::gauge ( const GaugeSpec & spec )

inline

◆ histogram()

Histogram prom::histogram ( const HistogramSpec & spec )

inline

◆ info()

Info prom::info ( const InfoSpec & spec )

inline

◆ is_valid_label_name()

constexpr bool prom::is_valid_label_name ( const std::string_view name )

constexprnoexcept

A label name follows the metric-name charset but additionally rejects the __ prefix, which OpenMetrics reserves for internal use.

◆ is_valid_metric_name()

constexpr bool prom::is_valid_metric_name ( std::string_view name )

constexprnoexcept

A metric name is valid when it matches Prometheus's [a-zA-Z_][a-zA-Z0-9_]*.

◆ normalize() [1/2]

template<DimensionalValue V>

NormalizedValue prom::normalize ( const V & value )

Reduce a dimval value to a NormalizedValue.

Measures expose both descriptor() (the measure descriptor) and unit_descriptor() (the base unit); units expose only descriptor() (which already is a unit descriptor). Either way we want the unit descriptor's long_name, kind, and symbol, so prefer unit_descriptor() when present.

◆ normalize() [2/2]

template<class T >
requires std::is_arithmetic_v<T>

NormalizedValue prom::normalize ( T value )

noexcept

Pass an arithmetic sample straight through with no unit attached.

◆ scope() [1/2]

std::shared_ptr< Scope > prom::scope ( const std::string_view name )

inline

Get-or-create the scope named name with a default config whose prefix is name + "_".

◆ scope() [2/2]

std::shared_ptr< Scope > prom::scope	(	const std::string_view	name,
		ScopeConfig	config
	)

inline

Get-or-create the process-wide scope named name, using config only if it does not yet exist (a later call returns the existing scope and ignores config — reconfigure through the returned scope's setters instead).

◆ scope_names()

std::vector< std::string > prom::scope_names ( )

inline

The names of every process-wide scope created so far (unordered).

◆ scopes()

std::vector< std::shared_ptr< Scope > > prom::scopes ( )

inline

Every process-wide scope created so far (unordered).

◆ stateset()

StateSet prom::stateset ( const StateSetSpec & spec )

inline

◆ summary()

Summary prom::summary ( const SummarySpec & spec )

inline

◆ to_string() [1/2]

constexpr std::string_view prom::to_string ( const ErrorCode code )

constexprnoexcept

Human-readable spelling of an ErrorCode.

◆ to_string() [2/2]

constexpr std::string_view prom::to_string ( const MetricType type )

constexprnoexcept

Lower-case OpenMetrics spelling of a MetricType (e.g. "counter").

◆ try_counter()

expected< Counter > prom::try_counter ( const CounterSpec & spec )

inlinenoexcept

◆ try_gauge()

expected< Gauge > prom::try_gauge ( const GaugeSpec & spec )

inlinenoexcept

◆ try_histogram()

expected< Histogram > prom::try_histogram ( const HistogramSpec & spec )

inlinenoexcept

◆ try_info()

expected< Info > prom::try_info ( const InfoSpec & spec )

inlinenoexcept

◆ try_stateset()

expected< StateSet > prom::try_stateset ( const StateSetSpec & spec )

inlinenoexcept

◆ try_summary()

expected< Summary > prom::try_summary ( const SummarySpec & spec )

inlinenoexcept

◆ try_untyped()

expected< Untyped > prom::try_untyped ( const UntypedSpec & spec )

inlinenoexcept

◆ untyped()

Untyped prom::untyped ( const UntypedSpec & spec )

inline

Variable Documentation

◆ default_histogram_buckets

constexpr std::array<double, 11> prom::default_histogram_buckets

inlineconstexpr

Initial value:

= {

0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10.0}

The default bucket bounds applied when a histogram spec leaves buckets empty — the canonical Prometheus client default set (seconds-oriented).

◆ default_summary_quantiles

constexpr std::array<double, 3> prom::default_summary_quantiles = {0.5, 0.9, 0.99}

inlineconstexpr

Default quantiles applied when a summary spec leaves quantiles empty.

Namespaces

Classes

Concepts

Typedefs

Enumerations

Functions

Variables

Typedef Documentation

◆ AdapterPtr

◆ expected

◆ MetricHandle

Enumeration Type Documentation

◆ ErrorCode

◆ MetricType

Function Documentation

◆ counter()

◆ describe()

◆ find_scope()

◆ gauge()

◆ histogram()

◆ info()

◆ is_valid_label_name()

◆ is_valid_metric_name()

◆ normalize() [1/2]

◆ normalize() [2/2]

◆ scope() [1/2]

◆ scope() [2/2]

◆ scope_names()

◆ scopes()

◆ stateset()

◆ summary()

◆ to_string() [1/2]

◆ to_string() [2/2]

◆ try_counter()

◆ try_gauge()

◆ try_histogram()

◆ try_info()

◆ try_stateset()

◆ try_summary()

◆ try_untyped()

◆ untyped()

Variable Documentation

◆ default_histogram_buckets

◆ default_summary_quantiles