Hello,

I have a monitor script that pings each and every machine to see if it is up. The results are then spit out into a database. I'm currently using a foreach over all my machine names which is slow. I wanted to convert the script to using background jobs instead, so all of the machines can be checked simultaneously.

I was wondering if I could get an explanation as to why it seems I can't pass information into start-job. Maybe I'm doing something wrong here but not sure.

$computers = "server1","server2"

foreach ($computer in $computers) { start-job {ping $computer} }

The job status fails every time I run this.

Another example:

foreach ($computer in $computers) { start-job { ./ping.ps1 $computer } }

ping.ps1 basically pings the computer and uses a redirect >> to a test.txt file


Is it not possibly to pass something into start-job or should I be using the pipeline instead?

Any suggestions on a better way to execute what I'm doing is welcome.

Thanks

Try it like this:
foreach($computer in $computers){invoke-expression "start-job {ping $computer}"}

That seems to work for me.

Marco's got it right. You need to keep in mind that a background job you create is run in a new session. The new session doesn't load the profile and doesn't have access to variables in your current session, so $computer is null in the background job. To fix that you need to evaluate $computer first and create the background job using the results of $computer. That's what Marco's script does.

Here's another approach, it creates one job (instead of one per computer) only and uses the builtin job functionality of the cmdlet:

$job = Test-Connection -ComputerName $computers -AsJob

You can also add the -ThrottleLimit parameter if you want to set the maximum number of concurrent connections that can be established to run this command. If you omit this parameter or enter a value of 0, the default value, 32, is used.

To get the results:

Receive-Job -job $job

Thanks for the quick responses. It seems that invoke-expression is what I was looking for.

However I seem to still have issues with start-job. Powershell might have an issue with port 80 since I'm running a web server on this host.

PS C:\> receive-job 121
Receive-Job : [localhost] Connecting to remote server failed with the following error message : The WinRM client sent a
request to an HTTP server and got a response saying the requested HTTP URL was not available. This is usually returned
by a HTTP server that does not support the WS-Management protocol.
At line:1 char:12
+ receive-job <<<< 121
+ CategoryInfo : OpenError: (:) [Receive-Job], PSRemotingTransportException
+ FullyQualifiedErrorId : RemoteRunspaceStateBroken

What is someone supposed to do if they want to run a web server on port 80 and powershell remoteing/background jobs?

Thanks again