RFR: 8288717: Add a means to close idle connections in HTTP/2 connection pool

[Jaikiran Pai]

On Tue, 6 Sep 2022 13:56:15 GMT, Conor Cleary <ccleary at openjdk.org> wrote:

> **Issue**
> When using HTTP/2 with the HttpClient, it can often be necessary to close an idle Http2 Connection before a server sends a GOAWAY frame. For example, a server or cloud based tool could close a TCP connection silently when it is idle for too long resulting in ConnectionResetException being thrown by the HttpClient.
> 
> **Proposed Solution**
> A new system property, `jdk.httpclient.idleConnectionTimeout`, was added and is used to specify in Milliseconds how long an idle connection (idle connections are those which have no currently active streams) for the HttpClient before the connection is closed.

src/java.net.http/share/classes/jdk/internal/net/http/Http2Connection.java line 200:

> 198:                 debug.log("HTTP connection idle for too long");
> 199:             }
> 200:             HttpTimeoutException hte = new HttpTimeoutException("HTTP connection idle, no active streams. Shutting down.");

Hello Conor,

The javadoc of `HttpTimeoutException` states "Thrown when a response is not received within a specified time period.", which isn't what we are using it for, here. Do you think we should instead just use a `Exception` (or some internal exception type) since this (as far as I can see) won't get propagated to the application?

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PR: https://git.openjdk.org/jdk/pull/10183