Main/Add-ExpiringCacheItem.ps1
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<#
.SYNOPSIS PowerShell implementation for Expiring Cache .DESCRIPTION Takes a ScriptBlock as execution and expiration policy. ScriptBlock is stored along with its expiration policy. Upon access, expiration policy is assessed. On expiration the given ScriptBlock is executed and the value is retrieved. This value is stored in the cache which is returned until its expiration. .EXAMPLE PS> Add-ExpiringCacheItem -Key '5sec' -ItemDefinition { Write-Output (Get-Date) } -Expiration '0:0:5' Adds a script block that is executed every time the cached item expires under the given key .EXAMPLE PS> Add-ExpiringCacheItem -Key '5sec' -ItemDefinition { Write-Output (Get-Date) } -Expiration '0:0:5' -Force Adds a script block that is executed every time the cached item expires under the given key. If an existing key already exists it gets overwritten .EXAMPLE PS> $c={$d=Get-Date;if($d -ge ([DateTime]'12/1/17 11:11:00 PM')){Write-Output $true}else{Write-Output $false}} PS> Add-ExpiringCacheItem -Key '5sec2' -ItemDefinition { Write-Output (Get-Date).ToString() } -CustomTrigger $c Creates a custom ScriptBlock, in this case returns true after the specified time, before this the cache is $null this value is returned back from the call #> function Add-ExpiringCacheItem { [CmdletBinding(DefaultParameterSetName = 'TimeSpan')] param( # A key to reference this item in the cache [Parameter(Mandatory, ParameterSetName = 'TimeSpan')] [Parameter(Mandatory, ParameterSetName = 'Custom')] [ValidateNotNullOrEmpty()] [string] $Key = '', # Execution context [Parameter(Mandatory, ParameterSetName = 'TimeSpan')] [Parameter(Mandatory, ParameterSetName = 'Custom')] [ValidateNotNullOrEmpty()] [ScriptBlock] $ItemDefinition, # Expiration policy [Parameter(Mandatory, ParameterSetName = 'TimeSpan')] [TimeSpan] $Expiration = '0:0:0', # Custom execution script to determine when to refresh the cache [Parameter(Mandatory, ParameterSetName = 'Custom')] [ValidateNotNull()] [ScriptBlock] $CustomTrigger = $null, # Whether to override any existing item with same key [Parameter(ParameterSetName = 'TimeSpan')] [Parameter(ParameterSetName = 'Custom')] [switch] $Force = $false ) $ErrorActionPreference = 'Stop' if ($script:expiringCacheObjects.Contains($Key) -and -not $Force) { throw [xUtilityException]::New( 'Add-ExpiringCacheItem', [xUtilityErrorCategory]::InvalidCacheKey, "Cache already contains an object with key '$Key'" ) } $cacheType = GetConfig('Module.ExpiringCache.CacheType') $triggerType = [ExpiringCacheItemType]::TimeSpanTrigger if ($CustomTrigger -ne $null) { $triggerType = [ExpiringCacheItemType]::CustomTrigger } $cacheItem = [PSCustomObject] @{ Expiration = $Expiration ItemDefinition = $ItemDefinition Item = $null LastRefresh = [DateTime] "January 1, 1" CustomTrigger = $CustomTrigger Type = $triggerType } $cacheItem.PSTypeNames.Insert(0, $cacheType) $script:expiringCacheObjects[$Key] = $cacheItem } |