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

[eirbjo]

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)

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Progress

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• Commit message must refer to an issue

Issue

• JDK-8304065: HttpServer.stop should terminate immediately if no exchanges are in progress (Bug - P4)

Reviewing

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[mlbridge]

Webrevs

• 00: Full (f06c8df5)

[dfuch]

I don't think that works unfortunately. We need something that takes into account that an exchange may have been started but hasn't reached the point where startExchange has been called.

The problem is that exchangeCount is incremeted asynchronously in the ExchangeImpl constructor, and the ExchangeImpl is created by the Exchange::run method - which is run asynchronoously in the executor (submitted by the dispacher thread).

Possibly posting a StopRequested event to the dispatcher thread, and have the dispacther thread switch finished = true when is sees the StopRequested event and notices that allConnections only contains idleConnections (in which case we could also assert that exchangeCount == 0).

Unless I'm not mistaken this is not going to be a trivial fix.

[eirbjo]

Unless I'm not mistaken this is not going to be a trivial fix.

Alright, I'll convert this to a draft PR for now. I may explore solutions, but it seems a full fix could be above my pay grade.

[dfuch]

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.