nginx serve index file from subfolders - http

Question

I would like to serve an index file from a root folder and one from a subfolder from root.
My nginx server conf looks as follows:
server {
listen 80;
server_name localhost;
root /data/;
index index.html index.htm index.txt;
location / {
}
location /a {
alias /data/a/;
}
}
and my directory structure looks as follows:
/data/:
a index.txt
/data/a:
index.txt
If I then do curl localhost, I get the contents of the file /data/index.txt.
But curl /localhost/a gives me a 301.
curl localhost/a/index.txt works.
Why can't I access my index.txt with curl /localhost/a ?
I tried using a root instead of alias in the location /a block and also tried to specify the index.txt for location /a, but no success.
I see similar posts, e.g.
Nginx location configuration (subfolders)
but couldn't yet find the answer.

Answer 1

The index directive works with URIs that end with a /:
So the URI / gives you the contents of /index.txt and /a/ gives you the contents of `/a/index.txt.
If you provide Nginx with a URI of a directory (but without a trailing /), the default behaviour is to redirect to the same URI, but with a trailing /.
This is just how the index directive works. See this document for details.
If you want something other than default behaviour you will have to do it manually using try_files. See this document for details.
For example, to return the contents of an index.txt file by providing the URI of the directory without a trailing /, use:
root /data;
location / {
try_files $uri $uri/index.txt =404;
}
Note that the location /a { ... } block is not necessary in either this example, or the example in your question.