[Nginx Body Filter] #nginx

example.com

server {
        set $response_body '';  #we must declare variables first, we cannot create vars in lua
        set $error_request_body '';
        set $error_response_body '';
        body_filter_by_lua '
            local resp_body = string.sub(ngx.arg[1], 1, 1000)  -- arg[1] contains a chunk of response content
            ngx.ctx.buffered = string.sub((ngx.ctx.buffered or "") .. resp_body, 1, 1000)
            if ngx.arg[2] then  -- arg[2] is true if this is the last chunk
              ngx.var.response_body = ngx.ctx.buffered
            end
        ';
        log_by_lua '
            if ngx.var.status ~= "200" and ngx.var.status ~= "201" and ngx.var.status ~= "302" then
                ngx.var.error_response_body = ngx.var.response_body
                ngx.var.error_request_body = ngx.var.request_body
            end
        ';

    location  /service-uri {
        ...
        access_log /var/log/nginx/service-uri-access.log timing_with_error_body;
        ...
    }
}

nginx.conf

http {
        ... 
        log_format timing_with_error_body '$remote_addr $http_x_forwarded_for [$time_local] '
            '"$request" $status $body_bytes_sent $request_time $upstream_response_time '
            '"$http_referer" "$http_user_agent" "$error_request_body" "$error_response_body"';

        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;
}