composite_adapter.hpp File Reference

CompositeAdapter — fan one metric out to several backends at once. More...

#include <prom/adapter.hpp>
#include <prom/fwd.hpp>
#include <prom/labels.hpp>
#include <prom/unit.hpp>
#include <logman/logman.hpp>
#include <algorithm>
#include <cstddef>
#include <initializer_list>
#include <memory>
#include <span>
#include <string_view>
#include <utility>
#include <vector>

Include dependency graph for composite_adapter.hpp:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Classes
class	prom::CompositeState
	Backend state for a composite family or child: the index-aligned bundle of the handles each wrapped adapter returned. More...
class	prom::CompositeAdapter
	A backend that forwards every call to a fixed set of child adapters. More...

Namespaces
namespace	prom

Detailed Description

CompositeAdapter — fan one metric out to several backends at once.

A CompositeAdapter holds a fixed list of child adapters and forwards every Adapter call to each of them. Install it like any other backend (set_adapter(std::make_shared<CompositeAdapter>(...))) to, for example, feed both a real prometheus-cpp backend and a test-recording backend from a single set of metrics, or to tee metrics to two exporters during a migration.

The wrinkle is that register_metric/resolve each return one MetricHandle, but every child hands back its own. The composite solves this by bundling the per-child handles into a CompositeState: the handle prom holds is a CompositeState whose handles[i] is the handle child i returned. Each mutation then dispatches handles[i] to child i.