AWS Instance Scheduler

AWS Instance Scheduler

#########################################################################################################################
#  Script name:   instanceScheduler.ps1		 
#  Version:   	  v0.1      
#  Date:     	  08Nov2014 
#  Author:        Eric Miller 	
#  Purpose:       start/stop ec2 instances on a schedule, with retries and SNS notifications on WARNING/FATAL events 
#  Usage:         ./instanceScheduler.ps1
#  Dependencies:  aws.ps1, logging.ps1
#  Notes:
#  In order to give the retries sufficient time to process,
#  do not schedule starts/stops closer together than $maxRetries * $retryIntervals seconds 
#  http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-ItemType-InstanceStateType.html
#  Valid values: 0 (pending) | 16 (running) | 32 (shutting-down) | 48 (terminated) | 64 (stopping) | 80 (stopped)	   
#########################################################################################################################

# Initialize logging and AWS session, see dependencies above
# aws.ps1 uses specific IAM role for this script, redact access/secret keys or omit this file in commits
. .\logging.ps1
. .\aws.ps1

# config
$scheduleFile = '.\schedule.txt'
$debug = $false #toggle $true/$false to turn console debugging on/off
$skipDays = @("Saturday","Sunday")
$chkInterval = 15 #secs
$retryInterval = 60 #secs
$maxRetries = 5 
$pendingChanges = @()

# get instances/schedules from $scheduleFile
function getSchedule
{
	$schedule = Get-Content $scheduleFile
	$instances = @()
	foreach ($line in $schedule)
	{
		if ($line.StartsWith("#") -or ($line.length -eq 0)){continue} # skip comments and blank lines
		try
		{
			$line = $line.split(",")
			$instance = New-Object PSObject
			Add-Member -InputObject $instance -MemberType NoteProperty -Name id -Value $line[0].Trim().ToLower()
			Add-Member -InputObject $instance -MemberType NoteProperty -Name startTime -Value $line[1].Trim()
			Add-Member -InputObject $instance -MemberType NoteProperty -Name stopTime -Value $line[2].Trim()
			Add-Member -InputObject $instance -MemberType NoteProperty -Name currState -Value $null			
			Add-Member -InputObject $instance -MemberType NoteProperty -Name desState -Value $null
			Add-Member -InputObject $instance -MemberType NoteProperty -Name retryCredits -Value $null		
			$instances += $instance
		}
		catch
		{
			log FATAL "check the schedule file for correct syntax, script terminating"
			exit
		}
	}
	return $instances
}


# main loop
while ($true)
{
	# load new schedule whenever script starts or schedule file is changed
	if(($((gci $scheduleFile).LastWriteTime) -gt $schedLastWrite) -or (!$schedLastWrite))
	{
		$instanceList = getSchedule
		$schedLastWrite = (gci $scheduleFile).LastWriteTime
		log INFO "script started or schedule modified, reading new schedule"
		if ($debug)
		{
			write-host "DEBUG: schedLastWrite- $schedLastWrite`n" -foregroundcolor yellow
			write-host "DEBUG: instances from getSchedule function:" -foregroundcolor yellow
			foreach ($instance in $instanceList){write-host $instance -foregroundcolor yellow}
		}
	}
	
	# if today is not a skip day, rock on
	$dow = (Get-Date).DayOfWeek.ToString()
    if (!$skipDays.contains($dow))
	{
		# add instance objects with a start or stop scheduled for this minute to $pendingChanges array
        $now = Get-Date -format "HHmm"
        foreach($instance in $instanceList)
        {
            if($instance.startTime -eq $now)
			{
				log INFO "added to pending: $($instance.id) / desired state *running* @ $($instance.startTime) / $maxRetries retries"
				$instance.desState = "running"
				$instance.retryCredits = $maxRetries
				$pendingChanges += $instance
			}

            if($instance.stopTime -eq $now)
			{
				log INFO "added to pending: $($instance.id) / desired state *stopped* @ $($instance.stopTime) / $maxRetries retries"
				$instance.desState = "stopped"
				$instance.retryCredits = $maxRetries
				$pendingChanges += $instance
			}
        }
	}

	# refresh instance states and remove any whose current state matches desired state
    if ($pendingChanges)
    {
	    foreach ($instance in $pendingChanges)
	    {
		    $currInstance = Get-EC2Instance $instance.id
		    $instance.currState = $currInstance.Instances.state.name.Value
		    if ($instance.currState -eq $instance.desState)
		    {
			    log INFO "removed from pending: $($instance.id), desired state *$($instance.desState)* achieved"
			    $pendingChanges = $pendingChanges -ne $instance
		    }
	    }
    }
	
	# if $pendingChanges still isn't empty, do stuff
	if ($pendingChanges)
	{
		foreach($instance in $pendingChanges)
		{
			if(($instance.desState -eq "stopped") -and ($instance.currState -eq "running")) #do nothing for pending, shutting-down, terminated, or stopping
            {
				log INFO "stopping $($instance.id)"
				try {$r = stop-ec2instance $instance.id} catch{log WARNING "problem with API call to stop $($instance.id)"}
				log INFO "ec2 response: instance = $($r.InstanceId), currentState = $($r.CurrentState.Name.Value), previousState = $($r.PreviousState.Name.Value)"
            }
			
			if(($instance.desState -eq "running") -and ($instance.currState -eq "stopped")) #do nothing for pending, shutting-down, terminated, or stopping
            {
				log INFO "starting $($instance.id)"
				try {$r = start-ec2instance $instance.id} catch {log WARNING "problem with API call to start $($instance.id)"}
				log INFO "ec2 response: instance = $($r.InstanceId), currentState = $($r.CurrentState.Name.Value), previousState = $($r.PreviousState.Name.Value)"
            }
			
			# decrement $retryCredits.
			# If instances hit $maxRetries, drop and send SNS notification (in logging)
			$instance.retryCredits -= 1
			if ($instance.retryCredits -eq 0)
			{
				log WARNING "removed from pending: ($instance.id), $maxRetries failed retries"
				$pendingChanges = $pendingChanges -ne $instance
			}
		}
		start-sleep -s $retryInterval
	}
	start-sleep -s $chkInterval
}