Really logging the POST request body (instead of "-") with nginx

Question

I'm trying to log POST body, and add $request_body to the log_format in http clause, but the access_log command just prints "-" as the body after I send POST request using:

curl -d name=xxxx myip/my_location 

My log_format (in http clause):

log_format client '$remote_addr - $remote_user $request_time $upstream_response_time '                   '[$time_local] "$request" $status $body_bytes_sent $request_body "$http_referer" '                   '"$http_user_agent" "$http_x_forwarded_for"'; 

My location definition(in server clause):

location = /c.gif {     empty_gif;     access_log logs/uaa_access.log client;   } 

How can I print the actual POST data from curl?

Answer 1

Nginx doesn't parse the client request body unless it really needs to, so it usually does not fill the $request_body variable.

The exceptions are when:

• it sends the request to a proxy,
• or a fastcgi server.

So you really need to either add the proxy_pass or fastcgi_pass directives to your block.

The easiest way is to send it to Nginx itself as a proxied server, for example with this configuration:

location = /c.gif {       access_log logs/uaa_access.log client;     # add the proper port or IP address if Nginx is not on 127.0.0.1:80     proxy_pass http://127.0.0.1/post_gif;  } location = /post_gif {     # turn off logging here to avoid double logging     access_log off;     empty_gif;   } 

If you only expect to receive some key-pair values, it might be a good idea to limit the request body size:

client_max_body_size 1k; client_body_buffer_size 1k; client_body_in_single_buffer on; 

I also received "405 Not Allowed" errors when testing using empty_gif; and curl (it was ok from the browser), I switched it to return 200; to properly test with curl.