I am trying to print the response data for development/debugging purposes. I couldn't find a similar question or any info on this. If you do, please add a comment.


3 Answers 3


Use body_filter_by_lua to assign request body to a nginx variable, here is an example:

worker_processes  1;
error_log logs/error.log;
events {
    worker_connections 1024;
http {
    log_format log_req_resp '$remote_addr - $remote_user [$time_local] '
        '"$request" $status $body_bytes_sent '
        '"$http_referer" "$http_user_agent" $request_time req_body:"$request_body" resp_body:"$resp_body"';

    server {
        listen 8082;
        access_log logs/access.log log_req_resp;

        lua_need_request_body on;

        set $resp_body "";
        body_filter_by_lua '
            local resp_body = string.sub(ngx.arg[1], 1, 1000)
            ngx.ctx.buffered = (ngx.ctx.buffered or "") .. resp_body
            if ngx.arg[2] then
                ngx.var.resp_body = ngx.ctx.buffered

        location / {
            echo "Hello World!";
  • 1
    In the code , we seem to be putting the first 1000 bytes from the response chunk and putting into resp_body i.e. in this line "resp_body = string.sub(ngx.arg[1], 1, 1000)". Is there a specific reason for this to be 1000.
    – doon
    Jun 2, 2015 at 11:51
  • In my case its not giving me response body but its giving me the path of log like this "resp_body:""access_log/usr/local/openresty/nginx/logs/access.logupstreamlog" Can you please suggest what's wrong?
    – SMT
    Mar 27, 2019 at 9:56

use ngx_lua module

like this

body_filter_by_lua 'ngx.log(ngx.CRIT,ngx.arg[1])';

in the right location

  • 1
    I think I'd prefer to use ngx.DEBUG. CRIT might get printed to the console, emailed to the whole sysadmin team, etc... Feb 15, 2013 at 8:08

I've found this one for example, and I think the echo module can also do it.

  • 2
    The echo module and the example provided talk about logging the request headers/body but I want to log the response body. Thanks petermolanar.
    – vamsu
    Feb 21, 2012 at 19:55

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