[HTTP/3] Implement connection scavenging

[geoffkizer]

We are not scavenging HTTP3 connections currently (i.e. based on idle timeout or lifetime). We need to implement this.

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Issue Details

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We are not scavenging HTTP3 connections currently (i.e. based on idle timeout or lifetime). We need to implement this.

Author:	geoffkizer
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	6.0.0

[karelz]

Triage: Would manifest as memory leak

[ManickaP]

@geoffkizer What exactly is missing? I see we check the expiration and dispose and clean up the connection:

runtime/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs

Lines 812 to 818 in f59a132

	if (CheckExpirationOnGet(http3Connection) || http3Connection.Authority != authority)
	{
	// Connection expired.
	if (NetEventSource.Log.IsEnabled()) http3Connection.Trace("Found expired HTTP3 connection.");
	http3Connection.Dispose();
	InvalidateHttp3Connection(http3Connection);
	}

[geoffkizer]

There's no HTTP3 logic here:

runtime/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs

Line 1971 in f59a132

public bool CleanCacheAndDisposeIfUnused()

[geoffkizer]

BTW, I think we should update the HTTP3 connection pooling logic in general to match the recent changes I made to HTTP11/2. As part of that, this should just fall out.

[geoffkizer]

I changed the milestone to 7.0. We can't deliver production quality HTTP3 without this.

[geoffkizer]

See also #60729, which has some proposals for how to change how connection scavenging works.

We should decide if we want to make any of those changes before we implement scavenging for HTTP3, to avoid wasted work.