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Extend prometheus.Registry to implement Collector #1103

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merged 3 commits into from Aug 23, 2022
Merged

Extend prometheus.Registry to implement Collector #1103

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97a08dd
prometheus: implement Collector interface for Registry
rfratto Aug 3, 2022
688d41e
fix grammar in doc comment
rfratto Aug 3, 2022
74ea536
document why Registry implements Collector with example
rfratto Aug 8, 2022
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31 changes: 28 additions & 3 deletions prometheus/registry.go
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Expand Up @@ -252,9 +252,9 @@ func (errs MultiError) MaybeUnwrap() error {
}

// Registry registers Prometheus collectors, collects their metrics, and gathers
// them into MetricFamilies for exposition. It implements both Registerer and
// Gatherer. The zero value is not usable. Create instances with NewRegistry or
// NewPedanticRegistry.
// them into MetricFamilies for exposition. It implements Registerer, Gatherer,
// and Collector. The zero value is not usable. Create instances with
// NewRegistry or NewPedanticRegistry.
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Do you mind adding a paraph about implementing Collector, it's behavior and what it enables?

Ideally we could add short ExampleRegistryGrouping example in test file too! 🤗

type Registry struct {
mtx sync.RWMutex
collectorsByID map[uint64]Collector // ID is a hash of the descIDs.
Expand Down Expand Up @@ -556,6 +556,31 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
return internal.NormalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
}

// Describe implements Collector.
func (r *Registry) Describe(ch chan<- *Desc) {
r.mtx.RLock()
defer r.mtx.RUnlock()

// Only report the checked Collectors; unchecked collectors don't report any
// Desc.
for _, c := range r.collectorsByID {
c.Describe(ch)
}
}

// Collect implements Collector.
func (r *Registry) Collect(ch chan<- Metric) {
r.mtx.RLock()
defer r.mtx.RUnlock()

for _, c := range r.collectorsByID {
c.Collect(ch)
}
for _, c := range r.uncheckedCollectors {
c.Collect(ch)
}
}

// WriteToTextfile calls Gather on the provided Gatherer, encodes the result in the
// Prometheus text format, and writes it to a temporary file. Upon success, the
// temporary file is renamed to the provided filename.
Expand Down