func ExtractFromEnv()

in tracing/env_extractor.go [16:57]

• 27 lines of code
• 4 McCabe index (conditional complexity)

func ExtractFromEnv(ctx context.Context, opts ...ExtractFromEnvOption) (context.Context, func()) {
	/* config not yet used */
	applyExtractFromEnvOptions(opts)

	tracer := opentracing.GlobalTracer()

	// Extract the Correlation-ID
	envMap := environAsMap(os.Environ())

	correlationID := envMap[envCorrelationIDKey]
	if correlationID != "" {
		ctx = correlation.ContextWithCorrelation(ctx, correlationID)
	}

	// Attempt to deserialize tracing identifiers
	wireContext, err := tracer.Extract(
		opentracing.TextMap,
		opentracing.TextMapCarrier(envMap))

	if err != nil {
		/* Clients could send bad data, in which case we simply ignore it */
		return ctx, func() {}
	}

	// Create the span referring to the RPC client if available.
	// If wireContext == nil, a root span will be created.
	additionalStartSpanOpts := []opentracing.StartSpanOption{
		ext.RPCServerOption(wireContext),
	}

	if correlationID != "" {
		additionalStartSpanOpts = append(additionalStartSpanOpts, opentracing.Tag{Key: "correlation_id", Value: correlationID})
	}

	serverSpan := opentracing.StartSpan(
		"execute",
		additionalStartSpanOpts...,
	)
	ctx = opentracing.ContextWithSpan(ctx, serverSpan)

	return ctx, func() { serverSpan.Finish() }
}