Public/Intrinsic Functions/Add-FnGetAZs.ps1
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function Add-FnGetAZs { <# .SYNOPSIS Adds the intrinsic function "Fn::GetAZs" to a resource property .DESCRIPTION The intrinsic function Fn::GetAZs returns an array that lists Availability Zones for a specified region. Because customers have access to different Availability Zones, the intrinsic function Fn::GetAZs enables template authors to write templates that adapt to the calling user's access. That way you don't have to hard-code a full list of Availability Zones for a specified region. ** Important ** For the EC2-Classic platform, the Fn::GetAZs function returns all Availability Zones for a region. For the EC2-VPC platform, the Fn::GetAZs function returns only Availability Zones that have a default subnet unless none of the Availability Zones has a default subnet; in that case, all Availability Zones are returned. Similarly to the response from the describe-availability-zones AWS CLI command, the order of the results from the Fn::GetAZs function is not guaranteed and can change when new Availability Zones are added. IAM permissions The permissions that you need in order to use the Fn::GetAZs function depend on the platform in which you're launching Amazon EC2 instances. For both platforms, you need permissions to the Amazon EC2 DescribeAvailabilityZones and DescribeAccountAttributes actions. For EC2-VPC, you also need permissions to the Amazon EC2 DescribeSubnets action. .LINK http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getavailabilityzones.html .PARAMETER Region The name of the region for which you want to get the Availability Zones. You can use the AWS::Region pseudo parameter to specify the region in which the stack is created. Specifying an empty string is equivalent to specifying AWS::Region. This is not required. If you would like to default this to the stack deployment region, simply exclude this parameter and call the function by itself. .EXAMPLE Add-FnImportValue -ValueToImport (Add-FnSub -String "`${NetworkStackNameParameter}-SubnetID") When the template is exported, this will convert to: {"Fn::ImportValue":{"Fn::Sub":"${NetworkStackNameParameter}-SubnetID"}} .NOTES You can use the Ref function in the Fn::GetAZs function. .FUNCTIONALITY Vaporshell #> [OutputType('Vaporshell.Function.GetAZs')] [cmdletbinding()] Param ( [parameter(Mandatory = $false,Position = 0)] [ValidateScript({ $allowedTypes = "Vaporshell.Function.Ref","System.String" if ([string]$($_.PSTypeNames) -match "($(($allowedTypes|ForEach-Object{[RegEx]::Escape($_)}) -join '|'))") { $true } else { throw "The Region parameter only accepts the following types: $($allowedTypes -join ", "). The current types of the value are: $($_.PSTypeNames -join ", ")." } })] $Region ) if (!$Region) { Write-Verbose "No region specified! Defaulting to deployment region" $obj = [PSCustomObject][Ordered]@{ "Fn::GetAZs" = (Add-FnRef "AWS::Region" -Verbose:$false) } } else { $obj = [PSCustomObject][Ordered]@{ "Fn::GetAZs" = $Region } } $obj | Add-ObjectDetail -TypeName 'Vaporshell.Function','Vaporshell.Function.GetAZs' Write-Verbose "Resulting JSON from $($MyInvocation.MyCommand): `n`n`t$($obj | ConvertTo-Json -Depth 5 -Compress)`n" } |