ML Services Can Fill The Plan Cache

Kevin Feasel

2018-01-04

Bugs, R

I have a post talking about a bug in SQL Server:

For now, the workaround I have is to restart the SQL Server service occasionally. You can see that I have done it twice in the above screenshot. Our application is resilient to short database downtimes, so this isn’t a bad workaround for us; it’s just a little bit of an annoyance.

One thing to keep in mind if you are in this scenario is that if you are running ML Services hundreds of thousands of times a day, your ExtensibilityData folders might have a lot of cruft which may prevent the Launchpad service from starting as expected. I’ve had to delete all folders in \MSSQL14.MSSQLSERVER\MSSQL\ExtensibilityData\MSSQLSERVER01 after stopping the SQL Server service and before restarting it. The Launchpad service automatically does this, but if you have a huge number of folders in there, the service can time out trying to delete all of them.  In my experience at least, the other folders didn’t have enough sub-folders inside to make it worth deleting, but that may just be an artifact of how we use ML Services.

It’s very unlikely to affect most shops, as we only notice it after running sp_execute_external_script millions of times, and that’s pretty abnormal behavior.

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