Nginx : Alternative to if inside location blocks for caching headers based on a variable

Question

I'm trying to use Nginx page caching instead of Wordpress caching. The caching seems to work fine, but I'm having trouble setting conditional caching headers based on a variable - whether a user is logged into wordpress. If a user is logged in I want no-cache headers applied, if not the page can be cached for a day by both Wordpress and the CDN. I'm finding I can only add one header inside an if statement.

I have read (but not fully understood, because it's late here) [if is evil][1]. I also found an answer on stack exchange (on my laptop, can't find it now) that said inside an if block only one add_header works.

Can anyone give me ideas for an alternative that might work better? I know I can combine the expires with the cache-control, but I want more headers in there, plus I want to understand and learn.

Here's a significantly simplified config with the relevant parts in place.

server { server_name example.com; set $skip_cache 0; # POST requests and urls with a query string should always go to PHP if ($request_method = POST) { set $skip_cache 1; } if ($query_string != "") { set $skip_cache 1; } # Don't cache uris containing the following segments. if ($request_uri ~* "/wp-admin/|/admin-*|/xmlrpc.php|wp-.*.php|/feed/|index.php|sitemap(_index)?.xml") { set $skip_cache 1; } # Don't use the cache for logged in users or recent commenters if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") { set $skip_cache 1; } location / { try_files $uri $uri/ /blog/index.php?args; } location ~ \.(hh|php)$ { fastcgi_keep_conn on; fastcgi_intercept_errors on; fastcgi_pass php; include fastcgi_params; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; # Cache Stuff fastcgi_cache CACHE_NAME; fastcgi_cache_valid 200 1440m; add_header X-Cache $upstream_cache_status; fastcgi_cache_methods GET HEAD; fastcgi_cache_bypass $skip_cache; fastcgi_no_cache $skip_cache; add_header Z_ABCD "Test header"; if ($skip_cache = 1) { add_header Cache-Control "private, no-cache, no-store"; add_header CACHE_STATUS "CACHE NOT USED"; } if ($skip_cache = 0) { add_header Cache-Control "public, s-maxage = 240"; expires 1d; add_header CACHE_STATUS "USED CACHE"; } add_header ANOTHER_HEADER "message"; } } 

Answer 1

An alternative to the if directive is the map directive. And assuming the CACHE_STATUS vs CACHE_STATIC is just a typo in your question, you could try this:

map $http_cookie $expires { default 1d; ~*wordpress_logged_in off; } map $http_cookie $control { default "public, s-maxage = 240"; ~*wordpress_logged_in "private, no-cache, no-store"; } map $http_cookie $status { default "USED CACHE"; ~*wordpress_logged_in "CACHE NOT USED"; } server { ... location ~ \.(hh|php)$ { ... expires $expires; add_header Cache-Control $control; add_header CACHE_STATUS $status; } } 

The map directives should be placed inside the http container (at the same level as the server block) as shown above.

The map directive is documented here.

Answer 2

I've come up with one solution myself, based on the answer @Richard Smith provided that didn't quite do what I needed. I've used the more cache-control header rather and dropped the unnecessary expires directive.

This sits inside the server block

if ($skip_cache = 1) { set $cacheControl "private, max-age=0, s-maxage=0, no-cache, no-store"; } if ($skip_cache = 0) { set $cacheControl "public, max-age=86400, s-maxage=86400"; } 

Then this goes inside every applicable location block

add_header Cache-Control $cacheControl; 

This means no "if" is required inside the location block. I think this solves the problem, but I'm still interested if anyone has alternative ideas.