Implement generate-request-id

Fixes https://github.com/kubernetes/ingress-nginx/issues/2546

docs/user-guide/nginx-configuration/configmap.md

@@ -105,6 +105,7 @@ The following table shows a configuration option's name, type, and the default v
 |[forwarded-for-header](#forwarded-for-header)|string|"X-Forwarded-For"|
 |[compute-full-forwarded-for](#compute-full-forwarded-for)|bool|"false"|
 |[proxy-add-original-uri-header](#proxy-add-original-uri-header)|bool|"true"|
+|[generate-request-id](#generate-request-id)|bool|"true"|
 |[enable-opentracing](#enable-opentracing)|bool|"false"|
 |[zipkin-collector-host](#zipkin-collector-host)|string|""|
 |[zipkin-collector-port](#zipkin-collector-port)|int|9411|
@@ -601,6 +602,10 @@ Append the remote address to the X-Forwarded-For header instead of replacing it.
 
 Adds an X-Original-Uri header with the original request URI to the backend request
 
+## generate-request-id 
+
+Ensures that X-Request-ID is defaulted to a random value, if no X-Request-ID is present in the request
+
 ## enable-opentracing
 
 Enables the nginx Opentracing extension. _**default:**_ is disabled

internal/ingress/controller/config/config.go

@@ -429,6 +429,10 @@ type Configuration struct {
 	// Default: false
 	ComputeFullForwardedFor bool `json:"compute-full-forwarded-for,omitempty"`
 
+	// If the request does not have a request-id, should we generate a random value?
+	// Default: true
+	GenerateRequestId bool `json:"generate-request-id,omitempty"`
+
 	// Adds an X-Original-Uri header with the original request URI to the backend request
 	// Default: true
 	ProxyAddOriginalUriHeader bool `json:"proxy-add-original-uri-header"`
@@ -546,6 +550,7 @@ func NewDefault() Configuration {
 		ForwardedForHeader:         "X-Forwarded-For",
 		ComputeFullForwardedFor:    false,
 		ProxyAddOriginalUriHeader:  true,
+		GenerateRequestId:          true,
 		HTTP2MaxFieldSize:          "4k",
 		HTTP2MaxHeaderSize:         "16k",
 		HTTPRedirectCode:           308,

rootfs/etc/nginx/template/nginx.tmpl

@@ -277,7 +277,9 @@ http {
     # If no such header is provided, it can provide a random value.
     map $http_x_request_id $req_id {
         default   $http_x_request_id;
+        {{ if $cfg.GenerateRequestId }}
         ""        $request_id;
+        {{ end }}
     }
 
     {{ if $cfg.ComputeFullForwardedFor }}