RFR: 8320687: sun.jvmstat.monitor.MonitoredHost.getMonitoredHost() throws unexpected exceptions when invoked concurrently [v3]

[Alan Bateman]

On Fri, 24 Nov 2023 11:46:20 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>>> Right now, the sole usage of the `monitoredHostServiceLoader` instance is within a `synchronized (monitoredHosts) {...}` block within a method. So it wouldn't require this `assert`.
>> 
>> Okay, I guess part of me wonders why this field is needed in the first place. Why can't getMonitoredHost just create a ServiceLoader instead instead of trying to share between threads?
>
>> > Right now, the sole usage of the `monitoredHostServiceLoader` instance is within a `synchronized (monitoredHosts) {...}` block within a method. So it wouldn't require this `assert`.
>> 
>> Okay, I guess part of me wonders why this field is needed in the first place. Why can't getMonitoredHost just create a ServiceLoader instead instead of trying to share between threads?
> 
> 
> It can and that works too. That was one of the alternatives I had initially tried. I explain in this previous comment https://github.com/openjdk/jdk/pull/16805#issuecomment-1825194163 the reason why I thought sharing the ServiceLoader might be better. Do you think I should just use the local ServiceLoader approach instead?

> It can and that works too. That was one of the alternatives I had initially tried. I explain in this previous comment [#16805 (comment)](https://github.com/openjdk/jdk/pull/16805#issuecomment-1825194163) the reason why I thought sharing the ServiceLoader might be better. Do you think I should just use the local ServiceLoader approach instead?

I assume almost all usages just fetch the iterator just once, in which case the provider cache doesn't help. So yes, I think I would be tempted to just remove the field and make this a lot simpler.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16805#discussion_r1404274170