#4846 - Redirect non-matched requests to new redirects service

modules/web/templates/adblockplus.org.conf.erb

 # XSS and clickjacking prevention headers
 
 set $csp_frame "";
 if ($uri ~ ^/(:?\w\w(_\w\w)?/)?(?:index|firefox|chrome|opera|android|internet-explorer|safari|yandex-browser|maxthon)?$|^/blog/)
 {
   set $csp_frame "; frame-src www.youtube-nocookie.com;";
 }
 add_header Content-Security-Policy "default-src 'self'; img-src * data:; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval' $csp_frame";
 add_header X-Frame-Options "sameorigin";
 
@@ skipping 336 matching lines @@
     set $link "contributors";
   }
   if ($arg_link = "whitelist")
   {
     set $link "faq_basics";
     set $anchor "#disable";
   }
 
   if ($link = "")
   {
-    return 404;
+    # If there is no match in the legacy redirects, let the new redirect service handle it:
+    rewrite ^ $scheme://adblockplus.to/$arg_link/legacy_redirect redirect;

[mathias, 2017/11/03 12:38:13]

I do not like the `/legacy_redirect` part. It looks like unnecessary CO2
production to me. Why should `adblockplus.org/redirect?link=foobar` not redirect
to `adblockplus.to/foobar`?

If we find that it makes sense to designate the heritage in similar fashion
after all (which I am not convinced of, but for the sake of argument), I would
suggest something that avoids the bytes which do not transport information
(`_redirect`) and in general put the classification first
(`adblockplus.to/legacy/$arg_link`).

[f.nicolaisen, 2017/11/03 12:54:04]

My idea was that this would be valuable for tracking usage before eventually
sunsetting the old redirect endpoint. This way we can use the new stats produced
for eyeo.to to track how much the old redirects are being used (and from where
they come).
Would that still be forward-compatible with using the new redirects URLs? As an
example, from #4687, I need this URL for whatever legacy reasons:

    adblockplus.org/redirect?link=privacy_friendly_ads

However, I also want to start using the new, nicer URL:

    adblockplus.to/privacy_friendly_ads

This would require a single entry in the eyeo.to hiera data (given this patch),
and I get a nice URL to share around, which makes it easier to convince
developers that they should use the new redirect service as well.

If we would require the /legacy/ classification, I would get the uglier
adblockplus.to/legacy/privacy_friendly_ads URL, and/or I would have to add a
second hiera entry for the "modern" redirect
adblockplus.to/privacy_friendly_ads. Unless I'm misunderstanding..

[f.nicolaisen, 2017/11/03 13:23:41]

Addressed this in PS2.

   }
 
   if (!-f "$document_root/$lang/$link")
   {
     set $lang "!!";
   }
   set $langtest "$arg_lang $lang";
   if ($langtest ~ "^(\w+)-(\w+) !!")
   {
     set $lang "$1_$2";
@@ skipping 61 matching lines @@
 location /403.html
 {
   try_files $uri @proxied;
 }
 location @proxied
 {
   proxy_pass https://server16.adblockplus.org;
   proxy_set_header Host adblockplus.org;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 }