The presentation I gave for the SQL PASS PowerShell Virtual Chapter on 1/18/2017

1. Multithreading in
PowerShell with runspaces
1/18/2017
Drew Furgiuele
Senior DBA, IGS Energy

2. 1/18/2017 2
About me
dfurgiuele@igsenergy.com
@pittfurg
http://www.port1433.com
http://www.genesface.com
Contact Info
I’m a Senior SQL Server DBA at
IGS Energy in Dublin, Ohio. I’ve
been using SQL Server since SQL
Server 2000 and I love it. I also
enjoy DevOps, release
management, and PowerShell.

3. AGENDA
1/18/2017 3
1. Multithreading in PowerShell: Why?
2. How it works
3. Differences between runspaces and Invoke-Job
4. Examples!

4. Multithreading with PowerShell
• Most PowerShell scripts execute serially
• Which is usually fine!
• … Except when it isn’t
• Some things don’t always run fast, despite all the
optimization in the world
• And if something runs “fast” when applied to n+1
targets, it might become slow
1/18/2017 4

5. Runspaces – The good
• Runspaces spin up new threads on an existing
process for parallel execution.
• Threads can be invoked asynchronously
• Can automatically manage the number of
threads executing (so you don’t overwhelm
your CPU)
• Can return pretty much anything you want
1/18/2017 5

6. Runspaces – The not so good
1/18/2017 6
• Can be complex to set up and configure
• Need monitored
• Need cleaned up
• Are hard to troubleshoot
• Modules don’t persist

7. “… so preoccupied with whether or not you could…”
• “…that you didn't stop to think if you should.”
• Multithreading is a great tool to keep in your
toolbox, but it’s not a hammer looking for a nail
• Ever heard of failing at scale?
• How about failing at scalex?
1/18/2017 7

8. Creating Runspaces
• CODE!
1/18/2017 8

9. What about Start-Job / Receive-Job?
• Start-Job incurs a lot of overhead
• No throttling
• Same goes for –AsJob and Invoke-Command
• Does have a –ThrottleLimit, but that just limits
concurrent commands, NOT sessions
• How much of a difference? Let’s see it in action.
1/18/2017 9

10. Practical Example #1
• Reading Error Logs
• Text parsing in PowerShell is an expensive, slow
process
• Breaking up the workload into threads can vastly
improve performance
1/18/2017 10

11. Practical Example
• Master Data Management
1/18/2017 11

12. Learning More
• Runspaces – Hey Scripting Guy!
https://blogs.technet.microsoft.com/heyscriptingguy/
2015/11/26/beginning-use-of-powershell-runspaces-
part-1/
• Runspaces simplified as much as possible:
https://blog.netnerds.net/2016/12/runspaces-
simplified/
• Joe Prox’s PoshRSJob:
https://github.com/proxb/PoshRSJob
1/18/2017 12

13. 1/18/2017 13
About me
dfurgiuele@igsenergy.com
@pittfurg
http://www.port1433.com
http://www.genesface.com
Contact Info
I’m a Senior SQL Server DBA at
IGS Energy in Dublin, Ohio. I’ve
been using SQL Server since SQL
Server 2000 and I love it. I also
enjoy DevOps, release
management, and PowerShell.