delete a specific cookie in lua

[Prashant Gaur]

Hello All,

In my lua code i am sending a subrequest to fcgi and i am getting cookies .

Here i have a requirement i want to delete a specific cookie coming from from fcgi.
My try:
ngx.header['Set_Cookie'] = {}

but here all cookies will reset i want to delete specific cookie of name extra_token

[Yichun Zhang (agentzh)]

Hello!

On Thu, Aug 7, 2014 at 4:24 AM, Prashant Gaur wrote:
> Here i have a requirement i want to delete a specific cookie coming from
> from fcgi.
> My try:
> ngx.header['Set_Cookie'] = {}
>
> but here all cookies will reset i want to delete specific cookie of name
> extra_token
>

Read all the cookie values of ngx.header["Set-Cookie"], let's say, it
is a Lua table. Remove that specific cookie from this Lua table. And
then set the new Lua table back to ngx.header["Set-Cookie"]. That's
it.

Regards,
-agentzh

[Aapo Talvensaari]

On Thursday, August 7, 2014 8:31:29 PM UTC+3, agentzh wrote:

Read all the cookie values of ngx.header["Set-Cookie"], let's say, it
is a Lua table. Remove that specific cookie from this Lua table. And
then set the new Lua table back to ngx.header["Set-Cookie"]. That's
it.

I think that the current API may lead to hard to debug bugs. Whenever you are setting (say cookie, or any other header multiple times), you need to use code something like this:

local cookiename  = "test="
local cookievalue = "1"
local cookies = ngx.header["Set-Cookie"]
local t = type(cookies)
if t == "table" then
    local found = false
    for i, cookie in ipairs(cookies) do
        if cookie:find(cookiename, 1, true) then

            cookies[i] = cookiename .. cookievalue
            found = true
            break
        end
    end
    if not found then
        cookies[#cookies + 1] = cookiename .. cookievalue
    end
elseif t == "string" then
    if cookies:find(k, 1, true) then
        cookies = cookiename .. cookievalue
    else
        cookies = { cookies, cookiename .. cookievalue }
    end
else
    cookies = cookiename .. cookievalue
end
ngx.header["Set-Cookie"] = cookies

Seems a little bit counter-intuitive.

Regards

Aapo

[Yichun Zhang (agentzh)]

Hello!

On Fri, Aug 8, 2014 at 1:45 AM, Aapo Talvensaari wrote:
>
> I think that the current API may lead to hard to debug bugs. Whenever you
> are setting (say cookie, or any other header multiple times), you need to
> use code something like this:
>

This one is different from the original use case that removes a header
entry fulfilling certain conditions while keeping other entries with
the same header name.

For your use case, we could add a new API function,
ngx.resp.add_header(), that blindly adds a new header entry regardless
existing header entries with the same name (just like the standard
"add_header" directive). Such that, you can do
"ngx.header['Set-Cookie'] = 'blah blah blah'". However, the
ngx.header.HEADER API is a low-level nginx-side operation that
removing things is always expensive. So it's better to buffer and
filter cookies, for example, on the Lua land, and inject everything
into the nginx data structures via the ngx.header API in the end.

Regards,
-agentzh

[Prashant Gaur]

Thanks agentzh and Aapo.