SharePoint 2013 BLOB Cache

Hi Devendra,

There is an old, but still relevant article in MSDN blogs, describing SharePoint's BLOB Caches nicely. Good to have the reference here.

<BlobCache 
     location="D:\BlobCache" 
     path="\.(gif|jpg|png|css|js)$" 
     maxSize="10" 
     max-age="86400" 
     enabled="false"
/>

In the preceding example:

• location is the directory where the cached files will be stored
• path specifies in the form of a regular expression which files are cached based on the file extension
• maxSize is the maximum allowable size of the disk-based cache in gigabytes
• max-age specifies the maximum amount of time in seconds that the client browser caches BLOBs downloaded to the client computer. If the downloaded items have not expired since the last download, the same items are not re-requested when the page is requested. The max-age attribute is set by default to 86400 seconds (that is, 24 hours), but it can be set to a time period of 0 or greater.
• enabled is a Boolean that disables or enables the cache. 

Coming back to your questions:

1. Now, a user B access the same page for the first time, would he get the files from the WFE cache or not? Assuming that the content shown the page is exactly the same for both the user i.e. no user specific contennt and it consists of CSS, images, JS files.

If a next after previous user accesses the same WFE and the same assets which were already cached on the specific WFE and assets still have the same ctag and they are not already cached in the browser, then yes, files from the BLOB storage will be used. 

2. Now, user A again access the same page i.e. after closing the browser (say in few mins) would he get the files from the WFE cache?

It's likely that a browser cache will be used, depending on max-age parameter passed and browser's specific settings, otherwise, from WFE's BLOB Cache.