Disable dispatcher caching for specific requests

[dylanmccurry]

I have created a filter for asset requests to DAM. For certain assets, I want to completely disable caching in the dispatcher and AEMaaCS CDN.

Is it enough to simply set the headers from Java, or do I need to also apply some logic in the dispatcher?

For instance, I am doing something like this:

    public static void removeResponseCaching(SlingHttpServletResponse response) {
        response.setHeader("Surrogate-Control", "no-store");
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate, max-age=0");
        response.setHeader("Dispatcher", "no-cache");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Expires", "0");
    }

However, I am noticing that cache control headers are still coming back for certain requests even though this code is being executed.

I am trying something like this in my vhost:

	<LocationMatch "^/content/.*\.coreimg.*\.(?i:jpe?g|png|gif|svg)$">
		<If "%{HTTP:Cache-Control} in { 'no-cache' }">
		   	Header unset Cache-Control
			Header unset Expires
			Header set Expires 0
			Header set Age 0
			Header set Cache-Control "no-cache"
			Header set Surrogate-Control "private"
		</If>
		<Else>
			Header set Cache-Control "max-age=2592000,stale-while-revalidate=43200,stale-if-error=43200,public,immutable" "expr=%{REQUEST_STATUS} < 400"
			Header set Age 0
		</Else>
	</LocationMatch>

If I make a request to the file and supply Cache-Control: no-cache on the request, then the response contains the proper Cache-Control: no-cache header.  However, if the request doesn't have the Cache-Control directive, it seems that the Cache-Control header is being set to 

[Kamal_Kishor]

@dylanmccurry : If you don't want to cache certain requests based on their glob patterns, you should create a rule in your dispatcher configuration. Please refer: https://experienceleague.adobe.com/en/docs/experience-manager-learn/ams/dispatcher/understanding-cac...

[dylanmccurry]

Can you create a glob pattern based on header values?

[Kamal_Kishor]

@dylanmccurry : glob pattern should be based on content (dam) path and not on header values.
You can refer other reply below from @arunpatidar and try with it for your use-case.

[dylanmccurry]

Thanks, I've found that I can do this from my vhost file:

	# Files from DAM: cache mutable resources for max 24h on CDN and background refresh after 12h to avoid MISS
	<LocationMatch "^/content/dam/.*$">
		# Unset existing Cache-Control and Expires headers if the request status is less than 400 and X-Dispatcher is not 'no-cache'
		Header unset Cache-Control "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"
		Header unset Expires "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"

		# Set Cache-Control header for browser caching for a max of 1 day
		Header always set Cache-Control "max-age=86400,stale-while-revalidate=14400,stale-if-error=43200,public,immutable" "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"

		# Set Surrogate-Control header for CDN caching for a max of 3 days
		Header always set Surrogate-Control "max-age=259200,stale-while-revalidate=86400,stale-if-error=172800" "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"
	</LocationMatch>

	# HTML pages: Cache for 5min with background refresh 15m on browser and 4h on CDN to avoid MISS, also incl. requests with query parameter
	# Cache-Control headers will be added for any response which doesn't have an X-Dispatcher header set to 'no-cache'
	<LocationMatch "^/content/.*\.html$">
		# Unset existing Cache-Control and Expires headers if the request status is less than 400 and X-Dispatcher is not 'no-cache'
		Header unset Cache-Control "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"
		Header unset Expires "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"

		# Set Cache-Control header for browser caching for a max of 5 minutes
		Header always set Cache-Control "max-age=300,stale-while-revalidate=900" "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"

		# Set Surrogate-Control header for CDN caching for a max of 5.5 minutes
		Header always set Surrogate-Control "stale-while-revalidate=330,stale-if-error=930" "expr=%{REQUEST_STATUS} < 400 && %{resp:X-Dispatcher} != 'no-cache'"

		# Error page caching by checking request status. Set it to a low value (e.g., 1 - 2 mins) in case content is being published
		Header always set Cache-Control "max-age=60,stale-while-revalidate=120" "expr=%{REQUEST_STATUS} == 404"
		Header always set Surrogate-Control "stale-while-revalidate=120,stale-if-error=120" "expr=%{REQUEST_STATUS} == 404"
	</LocationMatch>

	# If X-Dispatcher is set to no-cache, do not cache the response
	Header unset Expires "expr=%{resp:X-Dispatcher} == 'no-cache'"
	Header unset Cache-Control "expr=%{resp:X-Dispatcher} == 'no-cache'"
	Header unset Surrogate-Control "expr=%{resp:X-Dispatcher} == 'no-cache'"
	Header always set Cache-Control "private" "expr=%{resp:X-Dispatcher} == 'no-cache'"
	Header always set Surrogate-Control "private" "expr=%{resp:X-Dispatcher} == 'no-cache'"

So the general idea is that certain requests squelch caching by adding an 'X-Dispatcher: no-cache' header to the response.

[arunpatidar]

Hi @dylanmccurry 

If you skip caching images, it will impact performance heavily. so reconsider caching again.

But in order to deny caching for dispatcher add a rule something like below : more info

/0005 {
 /glob "/content/.*.coreimg.*.(svg|pdf)"
 /type "deny"
}

 
to disabled CDN cache add a cache-control header from vhost file , more info

<LocationMatch "^/content/.*\.(jpeg|jpg)$">
     Header set Cache-Control "max-age=0"
     Header set Age 0
   </LocationMatch>