[Feature Request] Prevent HttpClient port exhaustion

[bgavrilMS]

Which Version of MSAL are you using ?
4.11

Platform
net45, netcore

Affects confidential clients

Repro

1. Do not provide a custom IHttpFactory
2. Many threads AcquireToken (e.g. web site at scale)

Expected behavior
MSAL should work

Actual behavior
After some time, an exception from HttpClient occurs complaining about port exaustion.

Possible Solution
There is a solution on .net classic described here https://softwareengineering.stackexchange.com/questions/330364/should-we-create-a-new-single-instance-of-httpclient-for-all-requests

For .net core, the solution is to use IHttpClientFactory, which needs to be adapted. Microsoft.Identity.Web should showcase how to do this. A better default for MSAL needs some investigation.

[henrik-me]

@bgavrilMS, regarding .netcore, are there somethings we can do better by default in the library (and perhaps will make it easier for Identity.Web and others to do the right thing and or their custom thing)?

[bgavrilMS]

I'll have a look at this. We could add a simplified version of IHttpClientFactory, or even a static HttpClient.

[jmprieur]

See Azure-Samples/ms-identity-aspnet-webapp-openidconnect#38 for how the usage of SuggestedCacheKey and HasToken simplifies the token cache serialization in confidential client applications

cc: @bgavrilMS @jennyf19 @pmaytak @henrik-me @trwalke @neha-bhargava