S3 redirect to sub-directory - nginx

Question

I have site served from S3 with Nginx with following Nginx configuration.
server {
listen 80 default_server;
server_name localhost;
keepalive_timeout 70;
gzip on;
gzip_disable "msie6";
gzip_vary on;
gzip_proxied any;
gzip_comp_level 6;
gzip_buffers 16 8k;
gzip_http_version 1.1;
gzip_types text/plain text/css application/json application/x-javascript application/javascript text/xml application/xml application/xml+rss text/javascript;
location / {
proxy_pass http://my-bucket.s3-website-us-west-2.amazonaws.com;
expires 30d;
}
At present whenever I build new version, I just delete target bucket contain and upload new frontend files to it.
Since I am deleting bucket contain, there is no way I can go back to previous version of frontend even versioning is enabled on bucket. So want to upload new frontend files into version dir (for example 15) in S3 bucket and then setup a redirect from http://my-bucket.s3-website-us-west-2.amazonaws.com/latest to http://my-bucket.s3-website-us-west-2.amazonaws.com/15
anyone knows how this can be done ?

Answer 1

There are multiple ways to do this:
The easiest may be through a symbolic link, provided that your environment allows that.
ln -fhs ./15 ./latest
Another option is an explicit external redirect issued to the user, where the user would see the new URL; this has a benefit in that multiple versions could be accessed at the same time without any sort of synchronisation issues, for example, if a client decides to do a partial download, everything should still be handy, because they'll most likely be doing the partial download on the actual target, not the /latest shortcut.
location /latest {
rewrite ^/latest(.*) /15$1 redirect;
}
The final option is an internal redirect within nginx; this is usually called URL masquerading in some third-party applications; this may or may not be recommended, depending on requirements; an obvious deficiency would be with partial downloads, where a resume of a big download may result in corrupted files:
location /latest {
rewrite ^/latest(.*) /15$1 last;
}
References:
http://nginx.org/r/location
http://nginx.org/r/rewrite

Answer 2

One of the simple ways to handle this situation is using variables. You can easily import a file to set the current latest version. You will need to reload your nginx config when you update the version with this method.
Create a simple configuration file for setting the latest version
# /path/to/latest.conf
set $latest 15;
Import your latest configuration in the server block, and add a location to proxy to the latest version.
server {
listen 80 default_server;
server_name localhost;
# SET LATEST
import /path/to/latest.conf;
location / {
proxy_pass http://s3host;
expires 30d;
}
# Note the / at the end of the location and the proxy_pass directive
# This will strip the "/latest/" part of the request uri, and pass the
# rest like so: /$version/$remaining_request_uri
location /latest/ {
proxy_pass http://s3host/$latest/;
expires 30d;
}
...
}
Another way to do this dynamically would be to use lua to script this behavior. That is a little more involved though, so I will not get into that for this answer.