prom::Adapter Class Reference

The pluggable backend. More...

#include <adapter.hpp>

Inheritance diagram for prom::Adapter:

Public Member Functions
	Adapter ()=default
	Adapter (const Adapter &)=delete
Adapter &	operator= (const Adapter &)=delete
	Adapter (Adapter &&)=delete
Adapter &	operator= (Adapter &&)=delete
virtual	~Adapter ()=default
virtual std::string_view	backend_name () const noexcept=0
	Stable identifier of the backend (e.g. "null", "prometheus-cpp").
virtual MetricHandle	register_metric (const MetricMeta &meta) noexcept=0
	Register a metric family.
virtual MetricHandle	resolve (const MetricHandle &family, const Labels &dynamic) noexcept=0
	Resolve the labeled child of family for the given dynamic labels, creating it on first request.
virtual void	inc (const MetricHandle &handle, double amount) noexcept=0
	Increase the series behind handle by amount (counter/gauge).
virtual void	dec (const MetricHandle &handle, double amount) noexcept=0
	Decrease the series behind handle by amount (gauge).
virtual void	set (const MetricHandle &handle, double value) noexcept=0
	Set the series behind handle to value (gauge/untyped).
virtual void	observe (const MetricHandle &handle, double value) noexcept=0
	Record an observation against handle (histogram/summary).
virtual void	set_info (const MetricHandle &handle, std::span< const Label > labels) noexcept=0
	Replace the label set carried by an info metric.
virtual void	set_state (const MetricHandle &handle, std::string_view state, bool active) noexcept=0
	Set the boolean value of one member of a state set.
virtual void	set_unit (const MetricHandle &, const Unit &) noexcept
	Late unit inference hook.

Detailed Description

The pluggable backend.

Non-copyable, non-movable: an Adapter is owned through a shared_ptr and referenced by every metric bound to it.

Threading contract. Every method may be called concurrently from any thread. Backends are responsible for their own synchronization. No method throws — failures are absorbed (and ideally logged) by the backend.

Constructor & Destructor Documentation

Adapter() [1/3]

prom::Adapter::Adapter ( )

default

Adapter() [2/3]

prom::Adapter::Adapter ( const Adapter &  )

delete

Adapter() [3/3]

prom::Adapter::Adapter ( Adapter &&  )

delete

~Adapter()

virtual prom::Adapter::~Adapter ( )

virtualdefault

Member Function Documentation

backend_name()

virtual std::string_view prom::Adapter::backend_name ( ) const

pure virtualnoexcept

Stable identifier of the backend (e.g. "null", "prometheus-cpp").

Implemented in prom::prometheus_cpp::PrometheusCppAdapter, prom::CompositeAdapter, and prom::NullAdapter.

dec()

virtual void prom::Adapter::dec ( const MetricHandle &  handle, double  amount  )

pure virtualnoexcept

Decrease the series behind handle by amount (gauge).

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

inc()

virtual void prom::Adapter::inc ( const MetricHandle &  handle, double  amount  )

pure virtualnoexcept

Increase the series behind handle by amount (counter/gauge).

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

observe()

virtual void prom::Adapter::observe ( const MetricHandle &  handle, double  value  )

pure virtualnoexcept

Record an observation against handle (histogram/summary).

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

operator=() [1/2]

Adapter & prom::Adapter::operator= ( Adapter &&  )

delete

operator=() [2/2]

Adapter & prom::Adapter::operator= ( const Adapter &  )

delete

register_metric()

virtual MetricHandle prom::Adapter::register_metric ( const MetricMeta &  meta )

pure virtualnoexcept

Register a metric family.

Must return a non-null handle even on failure (fall back to an inert handle) so callers never have to null-check.

Implemented in prom::CompositeAdapter, prom::NullAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

resolve()

virtual MetricHandle prom::Adapter::resolve ( const MetricHandle &  family, const Labels &  dynamic  )

pure virtualnoexcept

Resolve the labeled child of family for the given dynamic labels, creating it on first request.

The backend owns the child cache. Must return a non-null handle.

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

set()

virtual void prom::Adapter::set ( const MetricHandle &  handle, double  value  )

pure virtualnoexcept

Set the series behind handle to value (gauge/untyped).

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

set_info()

virtual void prom::Adapter::set_info ( const MetricHandle &  handle, std::span< const Label >  labels  )

pure virtualnoexcept

Replace the label set carried by an info metric.

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

set_state()

virtual void prom::Adapter::set_state ( const MetricHandle &  handle, std::string_view  state, bool  active  )

pure virtualnoexcept

Set the boolean value of one member of a state set.

Implemented in prom::NullAdapter, prom::CompositeAdapter, and prom::prometheus_cpp::PrometheusCppAdapter.

set_unit()

virtual void prom::Adapter::set_unit ( const MetricHandle &  , const Unit &    )

inlinevirtualnoexcept

Late unit inference hook.

Called when a metric that declared no unit latches the unit of its first dimensional observation. Optional — backends that cannot rename a registered series may ignore it.

Reimplemented in prom::NullAdapter, and prom::CompositeAdapter.

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The documentation for this class was generated from the following file:

• include/prom/adapter.hpp