Can someone please explain how module caching works since what I observe doesn't quite make sense. 

I have a DNN site on 5.6.3. in the host the caching is set to Memory, and Heavy.

I have a News Articles Latest module on a page. This work as expected when the the caching is set to File, 0 seconds. However, I have customised the News Articles Latest module and it takes more time to process now. So the page load is about 7 seconds. This is long and I wanted to use caching to reduce it.

So I set the caching to File, 1200 seconds. Now the page loads in about a second, so all is good. 

Now suppose a new article is submitted to the main News Article module. This can happen every few days based on predefined schedule. The News Article Latest module should show it as well. When the cache setting is not set, the module updates and shows the new changes. But when the cache is set to File, 1200, the module doesn't update even after several days and this is what I don't understand about caching. 

Is it not supposed to update after the 1200 seconds has passed? Doesn't it mean the cache expires after 1200 seconds after which a new call will be made which would update the cache? 

Strangely enough, if I am logged in as admin, the module  shows the updated version even with the cache setting of File, 1200. 

Very puzzled. Please advise. 

Henry

Thanks Sebastian. That was a great clue. I checked the scheduler and it is active, however the history shows that it is failing. It runs every half an hour and it is failing every time:

Purge Module Cache
Purged Module cache for FileModuleCachingProvider. Purged Module cache for FileModuleCachingProvider. Purging Module cache task failed. 0.374 False

Then I checked the eventlog. Two errors are generated for each:

THREAD ID: 16
TYPE: DotNetNuke.Services.ModuleCache.PurgeModuleCache
EXCEPTION: String was not recognized as a valid DateTime.
RESCHEDULED FOR: 3/23/2012 6:44:41 AM
SOURCE: STARTED_FROM_TIMER
ACTIVE THREADS: 2
FREE THREADS: -1
READER TIMEOUTS: 0
WRITER TIMEOUTS: 0
IN PROGRESS: 2
IN QUEUE: 5

--

AssemblyVersion: 5.6.3
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 475333fb-dcbe-4904-b5db-7fef723823b3
InnerException: String was not recognized as a valid DateTime.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.DateTimeParse.Parse
StackTrace:
Message: System.FormatException: String was not recognized as a valid DateTime. at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles) at DotNetNuke.Services.ModuleCache.FileProvider.IsFileExpired(String file) at DotNetNuke.Services.ModuleCache.FileProvider.PurgeExpiredItems(Int32 portalId) at DotNetNuke.Services.ModuleCache.PurgeModuleCache.DoWork()

--

I have no idea what this error is about. What can I do to get rid of it? There is no information in the error that can suggest what is causing this.

is there an item in Eventviewer associated, which may contain additional details?
edit scheduler job and re-save. Clear History. Which language are you using? Did you try upgrading to latest DNN 5 or DNN 6 version?

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Cheers from Germany,
Sebastian Leupold

   

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