chore: import upstream snapshot with attribution

wrapper/monitoring/prometheus/options.go

@@ -0,0 +1,99 @@
+// Package prometheus provides a go-micro wrapper that exposes standard
+// request/response metrics (request count, latency, errors) to Prometheus.
+package prometheus
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// Options holds configuration for the Prometheus wrapper.
+type Options struct {
+	// Name is the metric name prefix (Prometheus "name").
+	// Default: "micro".
+	Name string
+
+	// Namespace for the Prometheus metrics.
+	// Default: "" (empty).
+	Namespace string
+
+	// Subsystem for the Prometheus metrics.
+	// Default: "" (empty).
+	Subsystem string
+
+	// ConstLabels are labels applied to every metric.
+	ConstLabels prometheus.Labels
+
+	// Buckets defines the histogram buckets (seconds) for latency.
+	// When nil, prometheus.DefBuckets is used.
+	Buckets []float64
+
+	// Registerer is used to register the metrics.
+	// When nil, prometheus.DefaultRegisterer is used.
+	Registerer prometheus.Registerer
+}
+
+// Option applies a single configuration value.
+type Option func(*Options)
+
+// ServiceName sets the metric name prefix (Prometheus "name").
+func ServiceName(name string) Option {
+	return func(o *Options) {
+		o.Name = name
+	}
+}
+
+// Namespace sets the Prometheus namespace for metrics.
+func Namespace(namespace string) Option {
+	return func(o *Options) {
+		o.Namespace = namespace
+	}
+}
+
+// Subsystem sets the Prometheus subsystem for metrics.
+func Subsystem(subsystem string) Option {
+	return func(o *Options) {
+		o.Subsystem = subsystem
+	}
+}
+
+// ConstLabels sets labels applied to every metric.
+func ConstLabels(labels prometheus.Labels) Option {
+	return func(o *Options) {
+		o.ConstLabels = labels
+	}
+}
+
+// Buckets sets the histogram buckets (in seconds) for latency metrics.
+func Buckets(buckets []float64) Option {
+	return func(o *Options) {
+		o.Buckets = buckets
+	}
+}
+
+// Registerer sets the Prometheus registerer used to register metrics.
+// When unset, prometheus.DefaultRegisterer is used.
+func Registerer(r prometheus.Registerer) Option {
+	return func(o *Options) {
+		o.Registerer = r
+	}
+}
+
+// newOptions builds Options from the provided Option functions, applying
+// sensible defaults.
+func newOptions(opts ...Option) Options {
+	options := Options{
+		Name:       "micro",
+		Buckets:    prometheus.DefBuckets,
+		Registerer: prometheus.DefaultRegisterer,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+	if options.Registerer == nil {
+		options.Registerer = prometheus.DefaultRegisterer
+	}
+	if len(options.Buckets) == 0 {
+		options.Buckets = prometheus.DefBuckets
+	}
+	return options
+}