In PowerShell Provider, when do you update cache data?

Question

I am writing a PowerShell provider in C #. The provider provides application domain objects through the drive interface. For instance:

my:\Users\ [e-mail] my:\Customers\Marty 

This data ultimately comes from the database.

I was not able to find a great guide for when you should go to the database for data, and when you should cache it. I believe that PowerShell names methods many times, such as ItemExists and GetChildNames; often repeated for the same team. It is incorrect to access the database 5 or 6 times just because, for example, they press the Tab key to end automatically.

But at the same time, as a user on the command line, if I type Get-ChildItem ( dir ) and look at the list, then do something outside of PowerShell so that I know that the data is updated, taking another directory listing should expect to see some or changes to the database.

I feel that if I knew the correct term to describe my problem (in PowerShell), I could answer Google or find an existing duplicate question, but I'm stuck.

Answer 1

This has very little to do with powershell and everything related to your data, and how important it is to update it. A simple caching scheme would be to use a temporary system in which, after N minutes, a request to your back level of data would pull out a new copy and reset the timer. It seems you already have an idea what your specific rules should be. I don’t think that two consecutive "dir" commands should always lead to two pulls from the backup storage, but you think so about this system. So do it.

UPDATE

Perhaps a simple guideline might be that you should update your data only once after issuing a vendor command. The list of built-in commands that work with provider items consists of:

• Clear item
• Copy-item
• Get-item
• Invoke-item
• Move-Item
• New-item
• Remove-Item
• Rename-Item
• Set-item

In addition, the list of built-in commands that work with the properties of a provider item consists of:

• Clear-ItemProperty
• Copy-ItemProperty
• Get-ItemProperty
• Move-ItemProperty
• New-ItemProperty
• Remove-ItemProperty
• Rename-ItemProperty
• Set-ItemProperty

And finally, for reading / writing content we use:

• Add content
• Clear content
• Get-content
• Set-content

Each of these commands has a corresponding method in NavigationCmdletProvider (for hierarchical data stores), and here you can update your data. When implementing the New / Move / Rename / Remove / Set / Clear methods and other data modification methods, you should use some optimistic concurrency methodology, since the provider instances in PowerShell are not single; at any time there can be one or more copies.

I wrote a provider that takes its implementation from a script, which might turn out to be a simpler prototype of things. See http://psprovider.codeplex.com/

Hope this helps.