PowerShell ThreadJobs
Published July 24, 2018PowerShell Jobs were introduced in PowerShell v2. While remoting got the attention in that release PowerShell Jobs are at least as important. PowerShell v6.1 preview 4 has introduced a new addition to the options for jobs – PowerShell ThreadJobs.
The real change is the addition of the Start-ThreadJob cmdlet. All other aspects of managing ThreadJobs are provided by the standard Jobs cmdlets.
PS> Get-Command *Job | select name Name ---- Debug-Job Get-Job Receive-Job Remove-Job Start-Job Start-ThreadJob Stop-Job Wait-Job
When you use Start-Job the job is run in the background on a SEPARATE PROCESS. You can see the PowerShell processes stopping and starting if you monitor via Task manager or another instance of PowerShell.
ThreadJobs run on a separate THREAD within the same process. Apart for the cmdlet name you start a threadjob in the same way as a traditional background job.
PS> Start-Job -ScriptBlock {Get-Service}
Id Name PSJobTypeName State HasMoreData Location Command
-- ---- ------------- ----- ----------- -------- -------
1 Job1 BackgroundJob Running True localhost Get-Service
PS> Start-ThreadJob -ScriptBlock {get-Service}
Id Name PSJobTypeName State HasMoreData Location Command
-- ---- ------------- ----- ----------- -------- -------
3 Job3 ThreadJob NotStarted False PowerShell get-Service
Notice the different job type name. The location changes from the localhost to PowerShell indicating its not a separate process.
To view jobs
PS> Get-Job Id Name PSJobTypeName State HasMoreData Location Command -- ---- ------------- ----- ----------- -------- ------- 1 Job1 BackgroundJob Completed True localhost Get-Service 3 Job3 ThreadJob Completed True PowerShell get-Service
To view results
PS> Receive-Job -Id 3 Status Name DisplayName ------ ---- ----------- Running AdobeARMservice Adobe Acrobat Update Service Stopped AJRouter AllJoyn Router Service Stopped ALG Application Layer Gateway Service Stopped AppIDSvc Application Identity etc
To clean up jobs
PS> Get-Job | Remove-Job PS> Get-Job
The advantage of ThreadJobs is that they are lighter on resource consumption because they are using a thread not a process. You can therefore run more ThreadJobs simultaneously compared to standard Jobs.
The disadvantage for ThreadJobs is that all of your jobs are running in the same process. If one crashes the process will most likely crash and you’ll lose everything.
The pros and cons of using ThreadJobs vs standard jobs must be addressed on a case by case basis. The ThreadJobs project has a bit more background - https://github.com/PaulHigin/PSThreadJob
ThreadJobs look to be a useful addition to the options for running background jobs.
