nginx lua req.set_uri with jump hangs

calin.don · 2013-04-05T01:01:40+00:00

Hello! On Tue, Apr 2, 2013 at 5:57 PM, Dave Kierans wrote: > I've got a quick question about openresty, Lua and EAGAIN error/return > codes. > >...

nginx lua req.set_uri with jump hangs

calin.don

Hi,

I'm trying to do an uri change with jump but the request hangs indefinitely.

Here is the server block:

server {

server_name test.lo;

error_log /var/log/nginx/t.log debug;

listen 127.0.100.2:80;

types {}

default_type 'text/plain';

rewrite_by_lua '

local args = ngx.var.args

if args == "jump" then

ngx.req.set_uri("/jump",true)

end

location /jump {

echo "Jump around!";

}

location / {

echo "$scheme://$http_host$request_uri";

}

Accessing http://test.lo?jump by issuing # curl -sD- 'http://test.lo?jump' doesn't output anything, just hangs.

Here is the relevant debug log:

2013/04/04 19:57:19 [debug] 14050#0: *5 malloc: 00000000011F9560:1024

2013/04/04 19:57:19 [debug] 14050#0: *5 posix_memalign: 00000000011F9970:4096 @16

2013/04/04 19:57:19 [debug] 14050#0: *5 http process request line

2013/04/04 19:57:19 [debug] 14050#0: *5 recv: fd:16 76 of 1024

2013/04/04 19:57:19 [debug] 14050#0: *5 http request line: "GET /?jump HTTP/1.1"

2013/04/04 19:57:19 [debug] 14050#0: *5 http uri: "/"

2013/04/04 19:57:19 [debug] 14050#0: *5 http args: "jump"

2013/04/04 19:57:19 [debug] 14050#0: *5 http exten: ""

2013/04/04 19:57:19 [debug] 14050#0: *5 http process request header line

2013/04/04 19:57:19 [debug] 14050#0: *5 http header: "User-Agent: curl/7.27.0"

2013/04/04 19:57:19 [debug] 14050#0: *5 http header: "Host: test.lo"

2013/04/04 19:57:19 [debug] 14050#0: *5 http header: "Accept: */*"

2013/04/04 19:57:19 [debug] 14050#0: *5 http header done

2013/04/04 19:57:19 [debug] 14050#0: *5 event timer del: 16: 1365094699779

2013/04/04 19:57:19 [debug] 14050#0: *5 generic phase: 0

2013/04/04 19:57:19 [debug] 14050#0: *5 rewrite phase: 1

2013/04/04 19:57:19 [debug] 14050#0: *5 test location: "/"

2013/04/04 19:57:19 [debug] 14050#0: *5 using configuration "/"

2013/04/04 19:57:19 [debug] 14050#0: *5 http cl:-1 max:1048576

2013/04/04 19:57:19 [debug] 14050#0: *5 rewrite phase: 3

2013/04/04 19:57:19 [debug] 14050#0: *5 rewrite phase: 4

2013/04/04 19:57:19 [debug] 14050#0: *5 lua rewrite handler, uri:"/" c:1

2013/04/04 19:57:19 [debug] 14050#0: *5 lua creating new thread

2013/04/04 19:57:19 [debug] 14050#0: *5 lua reset ctx

2013/04/04 19:57:19 [debug] 14050#0: *5 http cleanup add: 00000000011FA7D8

2013/04/04 19:57:19 [debug] 14050#0: *5 lua run thread, top:0 c:1

2013/04/04 19:57:19 [debug] 14050#0: *5 lua set uri jump to "/"

2013/04/04 19:57:19 [debug] 14050#0: *5 lua resume returned 1

2013/04/04 19:57:19 [debug] 14050#0: *5 lua thread yielded

2013/04/04 19:57:19 [debug] 14050#0: *5 lua thread aborting request with URI rewrite jump: "/jump?jump"

2013/04/04 19:57:19 [debug] 14050#0: *5 lua request cleanup

2013/04/04 19:57:19 [debug] 14050#0: *5 post rewrite phase: 5

2013/04/04 19:57:19 [debug] 14050#0: *5 uri changes: 11

2013/04/04 19:57:19 [debug] 14050#0: *5 test location: "/"

2013/04/04 19:57:19 [debug] 14050#0: *5 test location: "jump"

2013/04/04 19:57:19 [debug] 14050#0: *5 using configuration "/jump"

2013/04/04 19:57:19 [debug] 14050#0: *5 http cl:-1 max:1048576

2013/04/04 19:57:19 [debug] 14050#0: *5 rewrite phase: 3

2013/04/04 19:57:19 [debug] 14050#0: *5 rewrite phase: 4

2013/04/04 19:57:19 [debug] 14050#0: *5 lua rewrite handler, uri:"/jump" c:1

2013/04/04 19:57:19 [debug] 14050#0: *5 lua run write event handler

2013/04/04 19:57:19 [debug] 14050#0: *5 useless lua write event handler

The nginx version is 1.2.8 and lua version is 0.7.19.

I guess this is a bug? Or if this is the expected behavior, what whould be the proper way to trigger the location rematch?

agentzh

Hello!

On Thu, Apr 4, 2013 at 10:01 AM, Calin Don wrote:
> I'm trying to do an uri change with jump but the request hangs indefinitely.
>
[...]
>     rewrite_by_lua '
>         local args = ngx.var.args
>         if args == "jump" then
>             ngx.req.set_uri("/jump",true)
>         end
>     ';
>
>     location /jump {
>         echo "Jump around!";
>     }
>
>     location / {
>         echo "$scheme://$http_host$request_uri";
>     }
> }
>

Please note that unlike the "rewrite" directive from the standard
ngx_rewrite module, "rewrite_by_lua" always runs in the "rewrite"
phase instead of the "server rewrite" phase when it is used in the
server {} block directly. And all the locations in the current server
{} block inherit this rewrite_by_lua directive. So your config is
equivalent to

    location /jump {
       rewrite_by_lua '
           local args = ngx.var.args
           if args == "jump" then
               ngx.req.set_uri("/jump",true)
           end
       ';
       echo "Jump around!";
    }

     location / {
         rewrite_by_lua '
             local args = ngx.var.args
             if args == "jump" then
                 ngx.req.set_uri("/jump",true)
             end
         ';
         echo "$scheme://$http_host$request_uri";
     }

Have you seen the problem here? Yes, you're having infinitely
recursive rewrite in location /jump, which keeps rewriting to itself.

> Accessing http://test.lo?jump by issuing # curl -sD- 'http://test.lo?jump'
> doesn't output anything, just hangs.
>

Yeah, even if rewrite cycling happens, the request should not hang.
I've committed a one-line patch that fixes the hang:

https://github.com/chaoslawful/lua-nginx-module/commit/e9f9fdd

With the latest git master, you'll immediately get a 500 error page
and the following error in your nginx's error log file:

rewrite or internal redirection cycle while processing "/jump"

Best regards,
-agentzh