Cache cleared message every second in Azure Logs

Question

We are trying to figure our an issue where our LIVE sites are getting down for 10 minutes everyday. While going through the Azure logs I am getting the following Warning:

WARN web[standardValues] cache is cleared by Sitecore.Caching.Generics.Cache`1+DefaultScavengeStrategy[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] strategy. Cache running size was 2,2 MB.

WARN WebUtil.QueryStringCache cache is cleared by Sitecore.Caching.Generics.Cache`1+DefaultScavengeStrategy[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] strategy. Cache running size was 17,7 KB.

WARN SqlDataProvider - Prefetch data(web) cache is cleared by Sitecore.Caching.Generics.Cache`1+DefaultScavengeStrategy[[Sitecore.Data.ID, Sitecore.Kernel, Version=10.0.0.0, Culture=neutral, PublicKeyToken=null]] strategy. Cache running size was 100 MB.

My Question is:

Is this a normal behavior, because I don't see this in the other sites hosted?

Answer 1

These log file entries indicate that the respective caches have reached their size limit and have been cleared. This can obviously have an effect on the performance of the site as the server is under more load to render content and repopulate the caches. This might be responsible for your outage. You might see this in one hosted site and not others if the site is handling more requests or has been running for a longer time period that the others.

To resolve this you should tune your caches. Cache tuning is a well documented topic and Sitecore offer a very useful document - CMS Tuning Guide which still holds true for the latest versions. The process will generally consist of increasing the appropriate cache sizes, monitoring the logs for cache clear entries and repeating the process until you have a sensible trade-off between server RAM allocation and site performance.