Support HTTP persistent connections in Web Cmdlets

[stevenebutler]

PR Summary

Fis #12764

This PR addresses 12764 by using persistent HTTP connections when Invoke-WebRequest uses the -Session variable. It does this by

1. Tracking the HttpClient object in the saved WebRequestSession.
2. Monitoring properties in WebRequestSession and rebuilding the HttpClient if they are changed. This is done to ensure that existing scripts that might tweak parameters between invocations of IWR actually apply the changes so they will behave in a backwards compatible manner. When anything that impacts the HttpClient is changed, the persistent connection is abandoned by disposing the HttpClient and underlying HttpClientHandler and constructing a new one. A warning is logged when this occurs as it has a performance impact (though no worse than the existing behaviour).
3. To support point 2, many parameters are stored as internal set-only properties in the WebRequestSession so changes between invocations that would require a new connection can be detected and the handler rebuilt appropriately.

PR Context

This PR makes a considerable difference to performance when using Invoke-WebRequest or Invoke-RestMethod with sessions when multiple requests are made to the same host. This is particularly evident for HTTPS requests, as each HTTPS connection can take hundreds of milliseconds to establish.

This PR as written passes existing tests in WebCmdlets.Tests.ps1 and additional WebSession tests that verify the HttpClient is rebuilt when appropriate.

The PR provides as much backwards compatibility as possible at the expense of the complexity of tracking how the HttpClient used in the WebSession was constructed and recreating the HttpClient in the case it would have been constructed differently between invocations in scripts that assume it is okay to change parameters between invocations with the same WebSession.

This PR squashes the commits in the original PR#19173 following multiple round of reviews by @iSazonov and @CarloToso on a previous version of the PR. PR#19173 has been withdrawn due to number of commits and volume of review comments.

Performance Impact

Performance impact of maintaining HTTP connection persistence is measured by comparing PowerShell 7.3.3 with this PR using this simple script:

(Measure-Command {
    $null =Invoke-WebRequest https://postman-echo.com/get?i=1 -SessionVariable Session
    1..10 | ForEach-Object {
            $null =Invoke-WebRequest https://postman-echo.com/get?i=$_ -WebSession $Session
    }
}).ToString()

PowerShell 7.3.3

00:00:08.3019013

PR Branch

00:00:03.4589770

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[stevenebutler]

Codefactor is complaining about some tests that were not added by this PR using plain text as a password.

@CarloToso will that impact being able to merge this PR?

[CarloToso]

@stevenebutler Don't worry about those two codefactor issues, I introduced the in #19190

[pull-request-quantifier-deprecated]

This PR has 305 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

---

Quantification details

Label      : Large
Size       : +255 -50
Percentile : 70.5%

Total files changed: 5

Change summary by file extension:
.cs : +141 -50
.resx : +3 -0
.ps1 : +111 -0

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[stevenebutler]

I have squashed all commits into a single commit.

[adityapatwardhan]

@stevenebutler Thank you for your contribution!

[God-damnit-all]

@stevenebutler Thank you for your contribution!

I'm happy to see this merged. You can safely close #12764 now.

[ghost]

🎉v7.4.0-preview.2 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes

[tonyg00]

I tested Preview 2 and back to back invocations of Invoke-WebRequest and Invoke-RestMethod are not re-using ports, new ones are created.

[CarloToso]

@tonyg00 did you use the -SessionVariable and then -WebSession parameter?

[tonyg00]

I did not, I just executed, Invoke-WebRequest -uri which is the most common use case for me of these cmdlets.
What is the correct syntax for this?

[CarloToso]

Don't worry, it's a new feature, it's not yet documented.
I think this syntax should work:

Invoke-WebRequest -Uri -SessionVariable session
Invoke-WebRequest -Uri -WebSession $session

[tonyg00]

That is working, Thanks!!