RFR: 8304065: HttpServer.stop should terminate immediately if no exchanges are in progress

[Daniel Fuchs]

On Sat, 5 Apr 2025 10:23:33 GMT, Eirik Bjørsnøs <eirbjo at openjdk.org> wrote:

> Please help review this PR which improves `HttpServer::stop` termination timing to better fit user expectations.
> 
> This PR:
> 
> * Makes `ServerImpl::stop` continue without delay when there are no active exchanges during shutdown
> * Attempts to interrupt the dispatcher thread before joining it, giving long-living interruptible exchanges a chance to finish  early
> * Adds testing for boundary conditions with or without an active exchange, delay occurring before exhange completes and exchange completing before delay.
> 
> Additionally, `ServerImpl::stop` is updated to use `System::nanotime` instead of `System::currentTimeMillis` when calculating wait times.
> 
> The test relies on timing to assert the order of events. Not perfect, but it seems to work.
> 
> (This part of the code base is rather new to me. A bit of hand-holding should be expected when reviewing this PR)

src/jdk.httpserver/share/classes/sun/net/httpserver/ServerImpl.java line 238:

> 236:         selector.wakeup();
> 237:         long latest = System.nanoTime() + Duration.ofSeconds(delay).toNanos();
> 238:         while (activeExchanges() > 0 && System.nanoTime() < latest) {

Also the arithmetic is dubious since `System.nanoTime() + Duration.ofSeconds(delay).toNanos();` could overflow. You never want to compare `val1 < val2` - use `val2 - val1 > 0` instead.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24467#discussion_r2031352645