Bug in handling POST then sending a file back

[Maxim Dounin]

Hello!

On Sun, Jan 07, 2024 at 09:41:33PM -0500, Saint Michael wrote:

> I am using openresty and nginx.
> I send a file to the server, which is a POST operation.  Then the
> server processes the file and needs to send back a different file. I
> try to send a file with ng.exec("/static/file_name") and I get error
> 405 Not Allowed.
> But if I do a 302 redirect, it works.
> I imagine that Nginx feels bad about sending a file in a POST
> operation, but http does not have such a limitation.
> Is there a workaround for this?

As far as I can see from the Lua module docs, ngx.exec() you are 
using in your script does an internal redirect.  As the result, 
nginx ends up with a POST request to a static file, which is not 
something nginx can handle: it does not know what to do with data 
POSTed to a static file, hence the error.

If you've already processed POSTed data, and want to show some 
static message to a client, consider returning a redirect to the 
static file to the user, such as 303 (See Other), see 
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/303 for a 
good description.

If you are sure you want to return the file as a response to the 
POST request itself (this is generally a bad practice, since it 
will break page refresh and browser history navigation), consider 
returning the file directly from your script instead of trying to 
do an internal redirect.

-- 
Maxim Dounin
http://mdounin.ru/