Detect if header injected request_id before creating one

Author: gianrubio

docs/examples/customization/configuration-snippets/ingress.yaml

@@ -4,7 +4,7 @@ metadata:
   name: nginx-configuration-snippet
   annotations:
     nginx.ingress.kubernetes.io/configuration-snippet: |
-      more_set_headers "Request-Id: $request_id";
+      more_set_headers "Request-Id: $req_id";
 
 spec:
   rules:

docs/user-guide/annotations.md

@@ -207,7 +207,7 @@ Using this annotation you can add additional configuration to the NGINX location
 
 ```yaml
 nginx.ingress.kubernetes.io/configuration-snippet: |
-  more_set_headers "Request-Id: $request_id";
+  more_set_headers "Request-Id: $req_id";
 ```
 
 ### Default Backend

docs/user-guide/configmap.md

@@ -332,7 +332,7 @@ Example for json output:
 
 ```console
 log-format-upstream: '{ "time": "$time_iso8601", "remote_addr": "$proxy_protocol_addr",
-    "x-forward-for": "$proxy_add_x_forwarded_for", "request_id": "$request_id", "remote_user":
+    "x-forward-for": "$proxy_add_x_forwarded_for", "request_id": "$req_id", "remote_user":
     "$remote_user", "bytes_sent": $bytes_sent, "request_time": $request_time, "status":
     $status, "vhost": "$host", "request_proto": "$server_protocol", "path": "$uri",
     "request_query": "$args", "request_length": $request_length, "duration": $request_time,

internal/file/bindata.go

@@ -273,6 +273,13 @@ http {
         ''               $this_host;
     }
 
+    # Reverse proxies can detect if a client provides a X-Request-ID header, and pass it on to the backend server.
+    # If no such header is provided, it can provide a random value.
+    map $http_x_request_id $req_id {                                                 
+        default   $http_x_request_id;                                               
+        ""        $request_id;                                                      
+    }
+
     {{ if $cfg.ComputeFullForwardedFor }}
     # We can't use $proxy_add_x_forwarded_for because the realip module
     # replaces the remote_addr too soon