Which configuration must be applied to enable re-fetching of cached items based on Cache Headers sent by AEM

[JakeCham]

Which configuration must be applied to enable re-fetching of cached items based on Cache Headers sent by AEM ?

 /enableTTL true

 /enableTTL "1"

Thanks

[Raja_Reddy]

Hi @JakeCham 
You can use  /enableTTL "1"
try below steps 

/cache {
   ## The cacheroot must be equal to the document root of the webserver
   /docroot "${PUBLISH_DOCROOT}"
   ## sets the level upto which files named ".stat" will be created in the 
   ## document root of the webserver. when an activation request for some 
   ## handle is received, only files within the same subtree are affected 
   ## by the invalidation.
   #/statfileslevel "1"
   ## caches also authorized data
   /allowAuthorized "1"
   ## Flag indicating whether the dispatcher should serve stale content if
   ## no remote server is available.
   #/serveStaleOnError "0"
   ## the rules define, which pages should be cached. please note that
   ## - only GET requests are cached
   ## - only requests with an extension are cached
   ## - only requests without query parameters ( ? ) are cached
   ## - only unauthorized pages are cached unless allowUnauthorized is set to 1
   /rules {
      $include "/etc/httpd/conf.dispatcher.d/cache/* "
   # the invalidate section defines those pages which are 'invalidated' after
   # any activation. please note that, the activated page itself and all 
   # related documents are flushed on an modification. for example: if the 
   # page /foo/bar is activated, all /foo/bar.* files are removed from the
   # cache.
   /invalidate {
      /0000 {
         /glob "*"
         /type "deny"
      }
      /0001 {
         /glob "*.html"
         /type "allow"
      }
                       /0002 {
                               /glob "/etc/segmentation.segment.js"
                               /type "allow"
                       }
                       /0003 {
                               /glob "*/analytics.sitecatalyst.js"
                               /type "allow"
                       }

   }
   /allowedClients {
      ## By default block all IP from allowing to initiate the invalidation commands
      /0000 {
         /glob "*.*.*.*"
         /type "deny"
      }
      ## Allow certain IP's like publishers to invalidate cache
      $include "/etc/httpd/conf.dispatcher.d/cache/ams_publish_invalidate_allowed.any"
   }
   ## The ignoreUrlParams section contains query string parameter names that
   ## should be ignored when determining whether some request's output can be
   ## cached or delivered from cache.
   ## In this example configuration, the "q" parameter will be ignored. 
   #/ignoreUrlParams {
   #  /0001 { /glob "*" /type "deny" }
   #  /0002 { /glob "q" /type "allow" }
   #}

   ## Cache response headers next to a cached file. On the first request to
   ## an uncached resource, all headers matching one of the values found here
   ## are stored in a separate file, next to the cache file. On subsequent
   ## requests to the cached resource, the stored headers are added to the
   ## response.
   ## Note, that file globbing characters are not allowed here.
   /headers {
      "Cache-Control"
      "Content-Disposition"
      "Content-Type"
      "Expires"
      "Last-Modified"
      "X-Content-Type-Options"
   }
   ## A grace period defines the number of seconds a stale, auto-invalidated
   ## resource may still be served from the cache after the last activation
   ## occurring. Auto-invalidated resources are invalidated by any activation,
   ## when their path matches the /invalidate section above. This setting
   ## can be used in a setup, where a batch of activations would otherwise
   ## repeatedly invalidate the entire cache.
   #/gracePeriod "2"

   ## Enable TTL evaluates the response headers from the backend, and if they
   ## contain a Cache-Control max-age or Expires date, an auxiliary, empty file
   ## next to the cache file is created, with modification time equal to the
   ## expiry date. When the cache file is requested past the modification time
   ## it is automatically re-requested from the backend.
   # /enableTTL "1"
}  

[aanchal-sikka · Accepted solution]

Hello @JakeCham 

Please use 

/enableTTL "1"

- Ensure the Cache-Control: max-age=60 header. max-age can be any value

- Next set /enableTTL "1"

- You will need to restart Apache for this change to take effect:

sudo apachectl restart

There is an excellent repository of dispatcher experients. Do check this one https://github.com/adobe/aem-dispatcher-experiments/tree/main/experiments/enableTTL 

[HeenaMadan]

use /enableTTL "1" to refetch 

# Enable TTL evaluates the response headers from the backend, and if they
# contain a Cache-Control max-age or Expires date, an auxiliary, empty file
# next to the cache file is created, with modification time equal to the
# expiry date. When the cache file is requested past the modification time
# it is automatically re-requested from the backend.
/enableTTL "1"

set 

/headers {
"Cache-Control"

} and define max-age so that  After expiring, a browser must refresh its version of the resource by sending another request to a server.

for eg:

Cache-Control: max-age=120

It means returned resource is valid for 120 seconds, after which the browser has to request a newer version.