Is there a good way to verify the Blob Cache has been flushed on all servers?

Question

I have 3 WFEs on my farm and want to ensure that when I flush the blob cache, that the cache is actually cleared.

I ran the PowerShell code below on one WFE and checked the BlobCache on the disk (C:\BlobCache) and it did not change in size or file count.

$webApp = Get-SPWebApplication "http://mywebapp/"
[Microsoft.SharePoint.Publishing.PublishingCache]::FlushBlobCache($webApp)
Write-Host "Flushed the BLOB cache for:" $webApp

Questions
How do you flush the blob cache on all WFEs programatically?
How can you verify that the cache has actually been flushed?

Answer 1

The BLOB cache should be flushed on all servers running the Foundation Web service. When FlushBlobCache($webApp), the flush will not be immediate. As for how to tell, you can simply see if the property "blobcacheflushcount" is incremented by 1, or is a new property (if you haven't flushed the cache before) to confirm the Flush Command is queued. Just run:

$webApp.Properties["blobcacheflushcount"]

This won't tell you when it is complete. If you want to know that, you'll need to monitor the folder or ULS log one each server.