[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.