Synchronizing PowerShell background jobs

Question

If two background jobs are started from the same session, how can one of them determine that the other has finished? Initially I tried something like this:

$j1 = Start-Job {
    Start-Sleep -Seconds 5
    "j1 done"
}

$j2 = Start-Job {
    param($j)
    "j2 waiting..."
    $j | Wait-Job
    "j2 done"
} -ArgumentList $j1.Finished

$j1,$j2 | Receive-Job -Wait

Of course it doesn't work because $j2 only gets a serialized snapshot of $j1 (the job Status in the snapshot would never change); furthermore each background job has their own job repository so $j object appears to be bogus in the context of $j2.

The jobs can synchronize via the mutexes, filesystem (if on the same machine) or a DB, etc. but I'm wondering if powershell provides any remoting-friendly facilities for this?

Keith Hill · Answer 1 · 2013-01-15T23:56:18.907

1

I don't think that is going to work because the job objects are relative to their PowerShell session/runspace. The Start-Job cmdlet spins up a new runspace (typically a new process). I don't believe PowerShell events would work either because they also appear (according to docs) to be session specific. I would keep it simple and use a file - pass the path into both jobs.

edited Jan 15 '13 at 23:56

answered Jan 15 '13 at 23:50

Keith Hill

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353
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Yeah using files is OK (I used global mutexes, which I think are backed by the filesystem anyway) as long as everything's on the same machine, which is safe to assume given `Start-Job` (vs `Invoke-Command`). – Serguei Jan 16 '13 at 02:23

score 0 · Answer 2 · answered Aug 21 '16 at 13:06

0

try this - in PowerShell 3.0 and newer:

$j1 = Start-Job {
    Start-Sleep -Seconds 5
    "j1 done"
}

$j2 = Start-Job {
    "j2 waiting..."
    $Using:j1 | Wait-Job
    "j2 done"
}

$j1,$j2 | Receive-Job -Wait

answered Aug 21 '16 at 13:06

Ladislav

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3
10

Synchronizing PowerShell background jobs

2 Answers2