PowerShell中Job相关命令及并行执行任务详解

> Start-Job -ScriptBlock { sleep 5 }

> Start-Job -ScriptBlock { sleep 5; Write-Host "Hello world."; } | Wait-Job

$job = Start-Job -ScriptBlock { sleep 5; Write-Host "Hello world."; }
Wait-Job $job
Receive-Job -Job $job

> Get-Job | Wait-Job

Remove-Job *
#测试计时开始
$start_time = (Get-Date)
Start-Job -ScriptBlock { sleep 9; Write-Host "Hello myJob1."; } -Name "myJob1"
Start-Job -ScriptBlock { sleep 5; Write-Host "Hello myJob2."; } -Name "myJob2"
$taskCount = 2
while($taskCount -gt 0)
{
 foreach($job in Get-Job)
 {
  $state = [string]$job.State
  if($state -eq "Completed")
  { 
   Write-Host($job.Name + " 已经完成")
   Receive-Job $job
   $taskCount--
   Remove-Job $job
  }
 }
 sleep 1
}
"所有任务已完成" 
#得出任务运行的时间
(New-TimeSpan $start_time).totalseconds

function Run-Tasks
{
 Param
 (
  $taskArr,
  $parallelcount=1
 )
 #测试计时开始
 $startTime = (Get-Date)
  #移除本次会话中已有的所有后台任务
 Remove-Job *
 # 使用变量 $taskCount 保存还没有执行完成的任务数
 $taskCount = $taskArr.Length
 
 #判断设定的并行任务数是否超过当前任务队列中的任务数
 if($parallelCount -gt $taskArr.Length)
 {
  $parallelCount = $taskArr.Length
 }
 #启动初始任务
 foreach($i in 1..$parallelCount)
 {
  Start-Job $taskArr[$i - 1] -Name "task$i"
 }
 #初始任务完成后开始的任务
 $nextIndex = $parallelCount
 #当任务队列中还有任务时不断轮询已建立的任务，当一个后台任务结束时删除这个任务，
 #然后从任务队列中取出下一个任务进行执行，然后等待所有任务执行完成。
 while(($nextIndex -lt $taskArr.Length) -or ($taskCount -gt 0))
 {
  foreach($job in Get-Job)
  {
   $state = [string]$job.State
   if($state -eq "Completed")
   { 
    Write-Host($job.Name + " 已经完成，结果如下：")
    Receive-Job $job
    Remove-Job $job
    $taskCount--
    if($nextIndex -lt $taskArr.Length)
    { 
     $taskNumber = $nextIndex + 1
     Start-Job $taskArr[$nextIndex] -Name "task$taskNumber"
     $nextIndex++
    }
   }
  }
  sleep 1
 }
 "所有任务已完成"
 #得出任务运行的时间
 (New-TimeSpan $startTime).totalseconds
}

#定义 6 个任务
$task1 = {sleep 12; Write-Host "Hello myJob1."; }
$task2 = {sleep 5; Write-Host "Hello myJob2."; }
$task3 = {sleep 8; Write-Host "Hello myJob3."; }
$task4 = {sleep 3; Write-Host "Hello myJob4."; }
$task5 = {sleep 20; Write-Host "Hello myJob5."; }
$task6 = {sleep 15; Write-Host "Hello myJob6."; } 
#将 6 个任务写入到一个数组中作为任务队列
$taskArr = $task1, $task2, $task3, $task4, $task5, $task6
#运行数组中的任务，允许同时运行 4 个任务
Run-Tasks -taskArr $taskArr -parallelcount 4