Get request_body in set_by_lua directive

Server NGINX
1

I wont to parse the request_body in a lua script file but am unable to
access the request_body in set_by_lua_file directive. Is there any way
to access the headers/cookies/get/post ?

my conf structure is like

http{
server {
…

set_by_lua_file $myContent myFile.lua;

location @abcd {
   ...
}

}
}

Posted at Nginx Forum:

2

On Thu, Mar 15, 2012 at 6:59 PM, rishabh [email protected] wrote:

I wont to parse the request_body in a lua script file but am unable to
access the request_body in set_by_lua_file directive. Is there any way
to access the headers/cookies/get/post ?

The request body API will not work at all in the context of set_by_lua
and set_by_lua_file directives. You should use rewrite_by_lua,
rewrite_by_lua_file instead.

Regards,
-agentzh

3

thanks have figured it out.

Another concern is, Say the processing time of LUA file is 10 seconds
and the request completes in 4 seconds. So will the total time NGINX
take will be 10 secs or 14 secs ?

Here is how i have structured my conf

http {

   server {

          location / {
                 proxy_pass http://upstream123;
                 post_action @loglua;
          }

          location @loglua {
                 set $log '';
                 rewrite_by_lua_file /nginx/mylua.lua;
                 logformat format1 '$log';
                 access_log /var/log/nginx/newlog.log format1;
          }
   }

}

Posted at Nginx Forum:

4

On Mon, Mar 19, 2012 at 6:02 PM, rishabh [email protected] wrote:

server {
access_log /var/log/nginx/newlog.log format1;
}
}
}

I don’t think this question is really related to the ngx_lua module.
This is really a question about the behavior of the standard
“post_action” configure directive.

The answer can be trivially found out by preparing a small example:

location /test {
    echo_sleep 1;
    post_action @post;
}

location @post {
    echo_sleep 5;
}

Here we use ngx_echo module’s echo_sleep directive to do non-blocking
sleep to emulate the time of real processing and computation.

By using the “curl” utility to access the /test interface defined
above, we can only observe a delay of 1 sec:

$ time curl localhost:8080/test
real  0m1.009s
user  0m0.004s
sys  0m0.005s

But we can not really draw a conclusion from just this because “curl”
actively closes the connection as soon as when it sees the end of the
response (in this case, the “last chunk” sent from nginx). But nginx
will not really close the connection until the post_action thing
completes, as can be seen when we use telnet to do the HTTP request
outself:

$ telnet 127.0.0.1 8080
GET /test HTTP/1.1
Host: localhost
Connection: close

0

The “last chunk”, i.e., the “0\r\n\r\n” bytes, appears right after 1
sec’s delay but the current telnet session does not quit until another
5 sec is passed. That is, the nginx does not close the current
connection until 5 + 1 == 6 sec is passed.

If HTTP keepalive is enabled, the extra delay can make the second
request on the same connection much slower. But if HTTP keepalive is
disabled, we’re probably safe because most decent HTTP clients will
actively close the connection even if Nginx does not do that on the
server side.

Regards,
-agentzh

5

Hello!

On Sun, Apr 28, 2013 at 12:13 PM, maanas wrote:

Thanks it help me as well. I was trying to read request post body in
set_by_lua directive

No, the request body is not read yet at the phase where set_by_lua
(and those ngx_rewrite directives) runs. Try using the rewrite_by_lua
directive instead where you can call ngx.req.read_body() in Lua to
explicitly read the request body (otherwise the body is still not
read):

But note that by default, rewrite_by_lua always runs after those
ngx_rewrite directives like “set” or “if”. If you want the other way
around, just turn on the rewrite_by_lua_no_postpone directive:

Best regards,
-agentzh

6

Thanks it help me as well. I was trying to read request post body in
set_by_lua directive

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