Hi guys,

I have a problem with some of the requests sent to my Nginx load balancer, which reports (in the access_log configured to show $upstream_addr) that $upstream_addr is equal to "-", but only in a weird case where the post contains the word "del".

I'm using Nginx 1.10.0 packaged in Ubuntu 16.04.4, in a development cluster of VMs with Nginx serving as load balancer to serve a bunch Drupal 7 sites that an Apache+modPHP is serving (I could use Nginx+PHP-FPM but that's not the point here).

So it's a web-facing VM with Nginx that passes to another VM with Apache (through proxy_pass). No "effective" load balancing (only one upstream server in the backend block).

I've tried to maintain customizations to a reasonable minimum to avoid introducing too many variables.

Inside Drupal 7 (which I installed under the Apache backend server), I have nodes that I would like to edit.

Now, on several nodes, when I edit a textarea with whatever I like, everything works fine. The request is passed to Nginx, then to Apache, and I can see that in the access logs for both.

However, if the textarea contains the work "del" (I know... weird), then the request gets to Nginx and the $upstream_addr is generated as "-" and no request reaches the upstream server.

How can I debug that?
I've tried putting the error_log to "debug" but it's apparently not an error.
The access_log provides me with this weird case of $upstream_addr = '-', but that's all I get...

Thanks for your help!