Added nginx config examples for CORS headers, and CORS selective reflection

README.md

@@ -71,7 +71,14 @@ Header set Access-Control-Allow-Headers "origin, authorization, accept"
 ```
 Note that using "\*" leaves your graphite instance quite open so you might want to consider using "http://my.graphite-dom.ain" in place of "\*"
 
-If your Graphite web is proteced by basic authentication, you have to enable the HTTP verb OPTIONS, origin
+Here is the same thing, in nginx format:
+```
+add_header  "Access-Control-Allow-Origin" "*"; 
+add_header  "Access-Control-Allow-Credentials" "true";
+add_header  "Access-Control-Allow-Methods" "GET, OPTIONS";
+add_header  "Access-Control-Allow-Headers" "Authorization, origin, accept";
+```
+If your Graphite web is protected by basic authentication, you have to enable the HTTP verb OPTIONS, origin
 (no wildcards are allowed in this case) and add Access-Control-Allow-Credentials. This looks like the following for Apache:
 ```
 Header set Access-Control-Allow-Origin "http://mygrafana.com:5656"
@@ -86,7 +93,20 @@ Header set Access-Control-Allow-Credentials true
     </LimitExcept>
 </Location>
 ```
-
+And in nginx:
+```
+auth_basic            "Restricted";
+auth_basic_user_file  /path/to/my/htpasswd/file;
+if ($http_origin ~* (https?://[^/]*\.somedomain\.com(:[0-9]+)?)) {  #Test if request is from allowed domain, you can use multiple if
+    set $cors "true";                                               #statements to allow multiple domains, simply setting $cors to true in each one.
+}
+if ($cors = 'true') {
+    add_header  Access-Control-Allow-Origin $http_origin;           #this mirrors back whatever domain the request came from as authorized, as
+    add_header  "Access-Control-Allow-Credentials" "true";          #as long as it matches one of your if statements
+    add_header  "Access-Control-Allow-Methods" "GET, OPTIONS";
+    add_header  "Access-Control-Allow-Headers" "Authorization, origin, accept";
+}
+```
 # Roadmap
 - Improve and refine the target parser and editing
 - Improve graphite import feature