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

[Daniel Fuchs]

On Tue, 27 Sep 2022 14:44:00 GMT, Michael McMahon <michaelm 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.
>
> I'd agree 1200 sec (20 mins) is way too high. I would think 5-6 mins would be more appropriate.

After discussing with @Michael-Mc-Mahon  it seems there is a use case for being able to configure HTTP/1.1 and HTTP/2 keepAlive timeouts independently. It wouldn't be unusual to configure an HTTP/1.1 keepAlive to e.g. 3-5s to have the client close the connection before the sever does, but a better value for HTTP/2 might be in the range of e.g 60s. HTTP/2 specifies a graceful GOAWAY and PING mechanism that allow client & server to cooperate on / detect connection close, which (theoretically) should avoid attempting to reuse stale connections.

Maybe we could introduce a new system property, say "jdk.httpclient.keepalive.timeout.h2" which could be used to configure HTTP/2 keepAlive separately. The default value for this property could be taken from "jdk.httpclient.keepalive.timeout". So specifying "-Djdk.httpclient.keepalive.timeout=<timeout>" would configure a global timeout both for HTTP/1.1 and HTTP/2, but "-Djdk.httpclient.keepalive.timeout.h2=<timeout>" could override this value for HTTP/2 if needed.

-------------

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