chore: initial commit

internal/pkg/metrics/otel.go

@@ -0,0 +1,82 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package metrics
+
+import (
+	"context"
+
+	"github.com/rs/zerolog/log"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/propagation"
+	sdkresource "go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
+
+	"github.com/hexolan/stocklet/internal/pkg/config"
+)
+
+// Initiate the OpenTelemetry tracer provider
+func InitTracerProvider(cfg *config.OtelConfig, svcName string) *sdktrace.TracerProvider {
+	// Create resource and trace exporter (to otel-collector)
+	resource := initTracerResource(svcName)
+	exporter := initTracerExporter(cfg.CollectorGrpc)
+
+	// Create the trace provider
+	tp := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+
+		sdktrace.WithResource(resource),
+	)
+
+	otel.SetTracerProvider(tp)
+	otel.SetTextMapPropagator(propagation.TraceContext{})
+
+	return tp
+}
+
+// Establishes a connection to otel-collector over gRPC
+func initTracerExporter(collectorEndpoint string) sdktrace.SpanExporter {
+	ctx := context.Background()
+
+	exporter, err := otlptracegrpc.New(
+		ctx,
+		otlptracegrpc.WithEndpoint(collectorEndpoint),
+		otlptracegrpc.WithInsecure(),
+	)
+	if err != nil {
+		log.Panic().Err(err).Msg("otel: failed to start otlp gRPC exporter")
+	}
+
+	return exporter
+}
+
+// Prepare a tracer resource to use with the tracing provider
+func initTracerResource(svcName string) *sdkresource.Resource {
+	ctx := context.Background()
+
+	resource, err := sdkresource.New(
+		ctx,
+		sdkresource.WithAttributes(
+			semconv.ServiceName(svcName),
+		),
+	)
+	if err != nil {
+		log.Panic().Err(err).Msg("otel: failed to create tracer resource")
+	}
+
+	return resource
+}