Cannot move file after long running task - powershell

Question

I have a windows powershell script executed by Windows Task Scheduler. The powershell code starts an executable cli program (java), which creates it's own logfile, then when finished my powershell script tries to rename the file then upload it to a remote server. However, I'm finding that it only successfully uploads the file ever 3rd or 4th execution and am not sure why. The history in task scheduler provides no details as to what might have happened (file lock?). Any ideas on how I can solve this? Here is a basic example of what I'm doing:
$old_log_name = "old_logfilename"
$new_log_name = "new_logfilename"
C:\path\to\my-java-program.exe -pass -some -options
Move-Item -Path $old_log_name -Destination $new_log_name
gsutil cp $new_log_name gs://cool-bucket-with-cf
I'm certain that the problem is with renaming the file, and not with uploading it, because can see so in windows file explorer.
Should I be checking to see if the file is available to be renamed or not?
Edit (revised code based on comments below):
$app_version = "4.5.7"
$now = get-date
$now = $now.ToString("yyyyMMddhhmm")
$old_log_name = "D:\myapp_$app_version.log"
$new_log_name = "D:\myapp_servername_$app_version.$now.log"
$arguments = "-a -c C:\myapp\config\Stage-$app_version.xml"
Start-Process C:\myapp\bin\4.5.7\myapp.exe -ArgumentList $arguments -NoNewWindow -Wait
Move-Item -Path $old_log_name -Destination $new_log_name
gsutil cp $new_log_name gs://path-to-mybucket

Answer 1

Why don't you start a process with your java program, so it wait for it to exit ?
$old_log_name = "old_logfilename"
$new_log_name = "new_logfilename"
Start-Process C:\path\to\my-java-program.exe -ArgumentList "your options" -NoNewWindow -Wait
Move-Item -Path $old_log_name -Destination $new_log_name
gsutil cp $new_log_name gs://cool-bucket-with-cf
Update
Since this is a scheduled task, you need to add a new event log in order to log events from your script (you need administrative rights for this) :
New-EventLog -LogName Application -Source TheScriptThatCallsMyJavaProgram
Then, replace Start-Process call with the following (EventId is random here) :
Write-EventLog -LogName Application -Source TheScriptThatCallsMyJavaProgram -EventId 3001 -Message "my-java-program.exe is about to start" # This logs the start of the program
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "C:\path\to\my-java-program.exe"
$pinfo.Arguments = "your options"
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$p.WaitForExit()
Write-EventLog -LogName Application -Source TheScriptThatCallsMyJavaProgram -EventId 3002 -Message "my-java-program.exe is exited" # This logs the end of the program