config: use *float32 with nil instead of float32 with sentinel value

internal/ingress/controller/config/config.go

@@ -87,11 +87,6 @@ const (
 	// Parameters for a shared memory zone that will keep states for various keys.
 	// http://nginx.org/en/docs/http/ngx_http_limit_conn_module.html#limit_conn_zone
 	defaultLimitConnZoneVariable = "$binary_remote_addr"
-
-	// Default sentinel value for Configuration.DatadogSampleRate, indicating
-	// that the Datadog tracer should consult the Datadog Agent for sampling
-	// rates rather than use a configured value.
-	DatadogDynamicSampleRate = -1.0
 )
 
 // Configuration represents the content of nginx.conf file
@@ -713,7 +708,7 @@ type Configuration struct {
 
 	// DatadogSampleRate specifies sample rate for any traces created.
 	// Default: use a dynamic rate instead
-	DatadogSampleRate float32 `json:"datadog-sample-rate"`
+	DatadogSampleRate *float32 `json:"datadog-sample-rate",omitempty`
 
 	// MainSnippet adds custom configuration to the main section of the nginx configuration
 	MainSnippet string `json:"main-snippet"`
@@ -999,7 +994,7 @@ func NewDefault() Configuration {
 		DatadogEnvironment:                     "prod",
 		DatadogCollectorPort:                   8126,
 		DatadogOperationNameOverride:           "nginx.handle",
-		DatadogSampleRate:                      DatadogDynamicSampleRate,
+		DatadogSampleRate:                      nil,
 		LimitReqStatusCode:                     503,
 		LimitConnStatusCode:                    503,
 		SyslogPort:                             514,