Re: [nginx][HttpLuaModule] location.capture and headers

agentzh · 2012-09-21T02:54:50+00:00

Hello! On Thu, Sep 20, 2012 at 3:35 AM, James Hurst <ja...@riverratrecords.com> wrote: >> 1. set the parent request's request header before call...

Re: [nginx][HttpLuaModule] location.capture and headers

agentzh

Hello!

On Thu, Sep 20, 2012 at 11:00 AM, Antoine wrote:
>
> Before asking a very quick question, I'd like to thank you for your work
> nginx-related, it's efficient and quite well documented. :)
>

Glad you like it :)

> I'm currently trying to get specific fields of the response headers.
> If I do curl -v http://localhost/myurl, I get everything I want (body +
> headers) of course.
> But if I do res=location.capture("/myurl"), I get the body thanks to
> res.body, but I can't figure out how to get the content of the header.
> I do get res.header (which is a table, according to Lua), but I don't know
> what's in it,

You can use Lua's for loop structure to iterate through the res.header table:

    http://www.lua.org/manual/5.1/manual.html#2.4.5

Here is a complete example:

    location = /t {
        content_by_lua '
            res = ngx.location.capture("/sub")
            for k, v in pairs(res.header) do
                if type(v) == "table" then
                    ngx.say(k, ": ", table.concat(v, ","))
                else
                    ngx.say(k, ": ", v)
                end
            end
        ';
    }

    location = /sub {
        content_by_lua '
            ngx.header.foo = {32, 56, "hey"}
            ngx.header.bar = "hello world"
            ngx.say("hello world")
        ';
    }

And we can access /t like this:

    $ curl localhost/t
    Content-Type: text/plain
    foo: 32,56,hey
    bar: hello world

> and how to get specific fields like "Etag" or "Date" (nil
> value), even though I'm sure that they are returned somehow because curl
> does show them !
>

There is a "-i" option for curl that can display the response headers :)

I'm cc'ing the openresty-en mailing list to let more users see our
discussion here: https://groups.google.com/group/openresty-en You're
also very welcome to join us there ;)

Thanks!
-agentzh

toine-ml

Le jeudi 20 septembre 2012 20:54:50 UTC+2, agentzh a écrit :

I'm cc'ing the openresty-en mailing list to let more users see our
discussion here: https://groups.google.com/group/openresty-en You're
also very welcome to join us there ;)

Thanks ;)

Very clear answer for a n00b question. Here was mistake. I was trying to access res.header.Etag, instead of res.header.ETag.
Indeed, I kinda new that HTTP Headers were insensitive, and when I reached my URL through Firefox and its WebConsole (Tools/Developper...), the displayed header was "Etag : "blahblah""... So I copied it without thinking, and then I didn't even bother changing the case.

Now here's my question, I'd like a nginx location to capture another location while sending HTTP headers such as "If-Match"... But since I'm doing things step by step, I'd first like to manage resolving this :

I have the following location :
   location = /sub {
       content_by_lua '
           ngx.header.ETag= [["123"]]
           ngx.say("hello world")
       ';
   }

If I do curl -i http://localhost/sub, I do get the ETag field with a HTTP 200, but if I do something like curl -i http://to.larb.in/t -H "If-None-Match: \"123\""
I still get a 200, and not the expected HTTP 304.

Could anyone help me understand nginx behavior concerning this thing ?

Thanks!
Antoine

toine-ml

On 09/21/2012 02:47 PM, Antoine wrote:

[...]

Actually, I've tried reading manually the value attached to "If-Match"header of my request, then comparing it to a variable I have in thelocation I requested, and then exiting *manually* (ngx.exit()) with a304 or a 412 for instance.

Now, I'm sending a request to another server (a riak database), and tosee if I should change the value or not, I'm usingmore_set_input_headers 'If-Match: "$myEtag"'.This sorta works, I do get the response from this DB with a 412, a 304or a 20x.

But now, what if I wanna do that within a Lua script (lua_ngx power!)which is in a sub sub request. How can change the input header exactlywhen I want to, that is to say, just before I call my Riak database?Because, before that very call, I don't want the "If-Match" header to beset.

I hope the problem isn't too difficult to understand, all I know is thatI'm having trouble expressing it clearly, in a foreign language ;)


Thanks a lot for your help,

Antoine

agentzh

Hello!

On Fri, Sep 21, 2012 at 9:12 AM, Antoine <toi...@laposte.net> wrote:
> Now, I'm sending a request to another server (a riak database), and to see
> if I should change the value or not, I'm using more_set_input_headers
> 'If-Match: "$myEtag"'.
> This sorta works, I do get the response from this DB with a 412, a 304 or a
> 20x.
>
> But now,  what if I wanna do that within a Lua script (lua_ngx power!) which
> is in a sub sub request. How can change the input header exactly when I want
> to, that is to say, just before I call my Riak database?

Check out the following thread on this list:

    https://groups.google.com/group/openresty-en/browse_thread/thread/59997cb54214716f

Best regards,
-agentzh