What is the Reason why installing R creates 20 User IDs?
If you have installed SQL, you may have noticed that it creates twenty user ids as part of the installation process. To many people the automatic creation of a number for SQL Server User IDs is alarming, and they want to know what these IDs are for and who will be using them. The answer for who could be using those IDs, is just about anyone running R and they are going to be using the resources of the server to do it. If you are a DBA and want to figure out how to stop this, keep reading as I promise to tell you, after I provide some context about SQL Server and R internals.
R Server and Launchpad
When R Server is installed as part of SQL Server, one way you can check to see if it is installed is to look to see if the Launchpad service is running. When R code is running it does not run within SQL Server OS. It is by definition an external process and the Launchpad exe serves as a conduit between SQL Server and the space where R is running. If you want to know more about R and SQL Server Internals, this article I wrote for SQL Mag will provide a lot more details. Microsoft designed the Launchpad service so that other languages might someday also run as R does on SQL Server. It also supports a feature of R Server which I wrote about, context switching. Context Switching provides the ability for users to utilize Server memory instead of the memory on their computers for running R, and access is granted through the use of one of the twenty ids created when R is installed.
Launchpad Settings – Where the External Users are Referenced
There are many reasons why a DBA might want to not allow clients to access server memory as that will tax the server. Turning it off is relatively simple. Go to the SQL Server Management Console and select SQL Server Launchpad for the instance of SQL Server running R Server.
In the picture of the screen, the instance of SQL Server I have running R Services is in SS2016. Right click on the server and select Properties, then click on the Advanced tab. When looking at the number of external users allowed by default, the number might look familiar. The reason there are twenty User IDs created for R Server is because Launchpad allocates by default external twenty users to connect from SQL Server to run R. If you don’t want to allow external users to run on a server, you will need to prevent the users from connecting by not enabling them to run R. To run R, users need to have db_rrerole permissions. If they do not have that, they cannot run R. On the production server, it is probably best that this permission not be granted to non-system users.
Since the External Users created are used by SQL Server when running R, it is not possible to set the number of external users to 0 as the Launchpad Service will not run, and no R Code can be executed anywhere. If the number of external users is modified, Configuration Manager provides a prompt window as a restart is required. If the number of External Users is set to 0, the Launchpad Service will not start. When the Launchpad Service tries to start, it will generate Error 1053: The Service Did Not Start in a Timely Fashion. The number of users has to be at least 1 for the service to be able to communicate with the external R components. If you add or reduce the number of External Users, the IDs will be either created or deleted to match the number listed.
Let me know if you found this information regarding SQL Server R Service information by commenting or messaging me on twitter. If you are interested in finding out more regarding the internals of SQL Server and R, you might be interested in reading this Article about the topic. I would also like to thank Bob Ward b | t of the Microsoft for helping me better understand the SQL Server R internals, and for patiently answering my questions on the topic.
Data aficionado et SQL Raconteur