Fission meets OpenTelemetry (#2157)

* add opentracing section and otelCollectorEndpoint
* initialize OTLP exporter
* pkg/controller: changes for context propagation
* pkg/executor: changes for context propagation
* pkg/fetcher: changes for context propagation
* pkg/router: changes for context propagation
* pkg/storagesvc: changes for context propagation
* set no default value for otel collector endpoint
* update readme and add notes to charts
* move common code to pkg/utils/otel
* adding fn and env as attributes
* don't use otelhttp transport for websocket
* URL ignore with common filter UrlsToIgnore

Note: The web socket example does not work when using OTEL HTTP. Here is an issue related to that on open-telemetry/opentelemetry-js-contrib.

Signed-off-by: Gaurav Gahlot <gauravgahlot0107@gmail.com>
Co-authored-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/utils/otel/provider.go

@@ -0,0 +1,61 @@
+package otel
+
+import (
+	"context"
+	"os"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
+	"go.uber.org/zap"
+	"google.golang.org/grpc"
+)
+
+// Initializes an OTLP exporter, and configures the corresponding trace and metric providers.
+func InitProvider(logger *zap.Logger, serviceName string) (func(), error) {
+	collectorEndpoint := os.Getenv("OTEL_COLLECTOR_ENDPOINT")
+	if collectorEndpoint == "" {
+		logger.Info("skipping trace exporter registration")
+		return nil, nil
+	}
+
+	ctx := context.Background()
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			semconv.ServiceNameKey.String(serviceName),
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	traceExporter, err := otlptracegrpc.New(ctx,
+		otlptracegrpc.WithInsecure(),
+		otlptracegrpc.WithEndpoint(collectorEndpoint),
+		otlptracegrpc.WithDialOption(grpc.WithBlock()),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	bsp := sdktrace.NewBatchSpanProcessor(traceExporter)
+	tracerProvider := sdktrace.NewTracerProvider(
+		sdktrace.WithSampler(sdktrace.AlwaysSample()),
+		sdktrace.WithResource(res),
+		sdktrace.WithSpanProcessor(bsp),
+	)
+
+	otel.SetTracerProvider(tracerProvider)
+	otel.SetTextMapPropagator(propagation.TraceContext{})
+
+	// Shutdown will flush any remaining spans and shut down the exporter.
+	return func() {
+		err := tracerProvider.Shutdown(ctx)
+		if err != nil {
+			logger.Fatal("error shutting down trace provider", zap.Error(err))
+		}
+	}, nil
+}