PSCache
Generic PowerShell cache implementation
What is PSCache?
PSCache grew out of a need to abstract away a hashtable-based "caching" scheme that I personally found myself implementing over and over again. PSCache transparently caches the results from previous queries using a custom fetcher - a scriptblock that'll retrieve a value from elsewhere based on a single parameter.
Here's a simple example using PSCache as a transparent store for results returned from Get-ADUser:
Import-Module PSCache
$ADUserCache = New-PSCache -Fetcher { Get-ADUser $_ -Properties manager,title,employeeId }
# Fetch the user "jdoe" - this first cache-miss will cauce PSCache to call the `$Fetcher` scriptblock once and return the result
$ADUserCache.Get('jdoe')
# Fetch the user "jdoe" again - this time he'll be returned directly from the cache
$ADUserCache.Get('jdoe')Which eviction policies are supported?
PSCache version 0.1.1 comes with 3 optional eviction policy implementations:
Least Recently Used (LRU)
Simple LRU policy which evicts the least recently cached entry
# Create a cache for URL page titles
$PageTitleCache = New-PSCache { param($url) (Invoke-WebRequest $url).title } -EvictionPolicy LRU -Capacity 3
# Grab a few url page titles
$PageTitleCache.Get('https://google.com') # cache miss, cache count = 1
$PageTitleCache.Get('https://github.com') # cache miss, cache count = 2
$PageTitleCache.Get('https://google.com') # cache hit
$PageTitleCache.Get('https://stackoverflow.com') # cache miss, cache count = 3
$PageTitleCache.Get('https://bing.com') # cache miss, cache count = 3, 'https://github.com' evicted
$PageTitleCache.Get('https://github.com') # cache miss, cache count = 3, 'https://google.com' evicted
$PageTitleCache.Get('https://google.com') # cache miss, cache count = 3, 'https://stackoverflow.com' evictedMost Recently Used (MRU)
Simple MRU policy which evicts the most recently cached entry
# Create a cache for URL page titles
$PageTitleCache = New-PSCache { param($url) (Invoke-WebRequest $url).title } -EvictionPolicy MRU -Capacity 3
# Grab a few url page titles
$PageTitleCache.Get('https://google.com') # cache miss, cache count = 1
$PageTitleCache.Get('https://github.com') # cache miss, cache count = 2
$PageTitleCache.Get('https://google.com') # cache hit
$PageTitleCache.Get('https://stackoverflow.com') # cache miss, cache count = 3
$PageTitleCache.Get('https://bing.com') # cache miss, cache count = 3, 'https://stackoverflow.com' evicted
$PageTitleCache.Get('https://github.com') # cache hit
$PageTitleCache.Get('https://google.com') # cache hitLeast Frequently Used (LFU)
Simple LFU policy which evicts the least recently cached entry of those least frequently used
# Create a cache for URL page titles
$PageTitleCache = New-PSCache { param($url) (Invoke-WebRequest $url).title } -EvictionPolicy LFU -Capacity 3
# Grab a few url page titles
$PageTitleCache.Get('https://google.com') # cache miss, cache count = 1
$PageTitleCache.Get('https://github.com') # cache miss, cache count = 2
$PageTitleCache.Get('https://google.com') # cache hit
$PageTitleCache.Get('https://stackoverflow.com') # cache miss, cache count = 3
$PageTitleCache.Get('https://bing.com') # cache miss, cache count = 3, 'https://stackoverflow.com' evicted
$PageTitleCache.Get('https://github.com') # cache miss, cache count = 3, 'https://bing.com' evicted
$PageTitleCache.Get('https://google.com') # cache hitRoadmap
PSCache is currently very basic. Future plans include both time- and counter-based eviction policies (globally and per-key), as well as explicit cache size settings.