get response header in subrequest

ming.liu1123 · 2012-06-12T12:06:16+00:00

15.10 下下来先尝鲜下....2012/6/11 agentzh <age...@gmail.com> Hello! On Sun, Jun 10, 2012 at 5:54 PM, smal...

get response header in subrequest

ming.liu1123

I am confusing at how to get a specified response header in subrequest.

This is main:

local bres = ngx.location.capture("/backend", {args = { uri = request_uri } })

local my_header = bres.header["X-My-Header"]

And

location /backend {

internal;

set $xheader ' ';

proxy_pass "http://127.0.0.1:8080$arg_uri";

header_filter_by_lua '

if ngx.header["X-My-Header"] ~= nil then

ngx.var.xheader = ngx.header["X-My-Header"]

end

more_set_headers "X-My-Header: $xheader";

}

I didn't find how to get response header by standard nginx module, then I found header_filter_by_lua.

But as it is said, it didn't be supported in subrequest.

So can anyone give some advice?

Thanks

agentzh

Hello!

On Tue, Jun 12, 2012 at 12:06 PM, james_openresty
<ming....@gmail.com> wrote:
>             header_filter_by_lua '
>                 if ngx.header["X-My-Header"] ~= nil then
>                     ngx.var.xheader = ngx.header["X-My-Header"]
>                 end
>             ';
>             more_set_headers "X-My-Header: $xheader";

Here you made a mistake by assuming the more_set_headers directive
runs after header_filter_by_lua. But in fact, it runs in the opposite
order, i.e., more_set_headers runs before header_filter_by_lua
regardless how they're written in the nginx config file.

The correct way is to set response header directly from within your
Lua code for header_filter_by_lua, as in the following example (tested
on my side):

    location /main {
        content_by_lua '
            local res = ngx.location.capture("/sub")
            ngx.say("foo: ", res.header.foo)
            ngx.say("bar: ", res.header.bar)
        ';
    }

    location /sub {
        echo hello;
        more_set_headers "foo: FOO";
        header_filter_by_lua '
            ngx.header.bar = "BAR"
        ';
    }

Then GET /main yields the output:

    foo: FOO
    bar: BAR

We can see that both of more_set_headers and header_filter_by_lua
successfully inserted a new response header for the subrequest GET
/sub, and they were also successfully grabbed by the parent request's
Lua code.

> I didn't find how to get response header by standard nginx module, then I
> found header_filter_by_lua.
> But as it is said, it didn't be supported in subrequest.

Manipulating subrequest's response headers are surely supported. But
you have to be very careful about the running order of various nginx
directives. Here is another example for this:

    https://github.com/chaoslawful/lua-nginx-module/issues/125#issuecomment-6261839

It shows how to pass $upstream_cache_status value from within the
subrequest to the parent request's Lua code via inserting new response
headers for the subrequest.

> So can anyone give some advice?

See above :)

Best regards,
-agentzh

ming.liu1123

It worked following your advice

Thanks a lot!

在 2012年6月12日星期二UTC+8下午12时06分15秒，james_openresty写道：

Hi
I am confusing at how to get a specified response header in subrequest.
This is main:
local bres = ngx.location.capture("/backend", {args = { uri = request_uri } })
local my_header = bres.header["X-My-Header"]

And
location /backend {
internal;
set $xheader ' ';
proxy_pass "http://127.0.0.1:8080$arg_uri";
header_filter_by_lua '
if ngx.header["X-My-Header"] ~= nil then
ngx.var.xheader = ngx.header["X-My-Header"]
end
';
more_set_headers "X-My-Header: $xheader";
}

I didn't find how to get response header by standard nginx module, then I found header_filter_by_lua.
But as it is said, it didn't be supported in subrequest.
So can anyone give some advice?
Thanks

lhmwzy

莫明其妙呢，谁给建议了，建议在哪里，建议是什么？