zero/telemetry: internal envoy stats scraper and metrics producer (#5136)

internal/telemetry/prometheus/producer.go

@@ -0,0 +1,147 @@
+package prometheus
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"sync/atomic"
+	"time"
+
+	"go.opentelemetry.io/otel/sdk/instrumentation"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+)
+
+type producerConfig struct {
+	client    *http.Client
+	scrapeURL string
+	scope     instrumentation.Scope
+	startTime time.Time
+	metrics   map[string]struct{}
+	labels    map[string]struct{}
+}
+
+type ProducerOption func(*producerConfig)
+
+func WithClient(client *http.Client) ProducerOption {
+	return func(cfg *producerConfig) {
+		cfg.client = client
+	}
+}
+
+func WithScope(scope instrumentation.Scope) ProducerOption {
+	return func(cfg *producerConfig) {
+		cfg.scope = scope
+	}
+}
+
+func WithStartTime(startTime time.Time) ProducerOption {
+	return func(cfg *producerConfig) {
+		cfg.startTime = startTime
+	}
+}
+
+func WithIncludeMetrics(metrics ...string) ProducerOption {
+	return func(cfg *producerConfig) {
+		if cfg.metrics == nil {
+			cfg.metrics = make(map[string]struct{}, len(metrics))
+		}
+		for _, metric := range metrics {
+			cfg.metrics[metric] = struct{}{}
+		}
+	}
+}
+
+func WithIncludeLabels(labels ...string) ProducerOption {
+	return func(cfg *producerConfig) {
+		if cfg.labels == nil {
+			cfg.labels = make(map[string]struct{}, len(labels))
+		}
+		for _, label := range labels {
+			cfg.labels[label] = struct{}{}
+		}
+	}
+}
+
+func WithScrapeURL(scrapeURL string) ProducerOption {
+	return func(cfg *producerConfig) {
+		cfg.scrapeURL = scrapeURL
+	}
+}
+
+func newProducerConfig(opts ...ProducerOption) *producerConfig {
+	cfg := &producerConfig{
+		client: http.DefaultClient,
+	}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return cfg
+}
+
+type Producer struct {
+	producerConfig atomic.Value
+}
+
+func NewProducer(opts ...ProducerOption) *Producer {
+	cfg := newProducerConfig(opts...)
+
+	p := new(Producer)
+	p.setConfig(cfg)
+	return p
+}
+
+func (p *Producer) UpdateConfig(opts ...ProducerOption) {
+	cfg := *p.loadConfig()
+	for _, opt := range opts {
+		opt(&cfg)
+	}
+	p.setConfig(&cfg)
+}
+
+func (p *Producer) Produce(ctx context.Context) ([]metricdata.ScopeMetrics, error) {
+	cfg := p.loadConfig()
+
+	if len(cfg.metrics) == 0 {
+		return nil, nil
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, cfg.scrapeURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	resp, err := cfg.client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to do request: %w", err)
+	}
+	defer resp.Body.Close()
+	metrics, err := ToOTLP(resp.Body, filter(cfg.metrics), filter(cfg.labels), cfg.startTime, time.Now())
+	if err != nil {
+		return nil, fmt.Errorf("failed to convert metrics to OTLP: %w", err)
+	}
+	return []metricdata.ScopeMetrics{
+		{
+			Scope:   cfg.scope,
+			Metrics: metrics,
+		},
+	}, nil
+}
+
+func (p *Producer) setConfig(cfg *producerConfig) {
+	p.producerConfig.Store(cfg)
+}
+
+func (p *Producer) loadConfig() *producerConfig {
+	return p.producerConfig.Load().(*producerConfig)
+}
+
+func filter(src map[string]struct{}) func(k string) (string, bool) {
+	return func(k string) (string, bool) {
+		if len(src) == 0 {
+			return k, true
+		}
+		if _, ok := src[k]; ok {
+			return k, true
+		}
+		return "", false
+	}
+}