ScheduledReporter reports metrics when stopped/closed even when not started

[ummels]

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ScheduledReporter's close method calls its stop method, which calls report to report the metrics "one last time". This also happens if start has never been called.

In a SpringBoot application that registers a ScheduledReporter as a bean, this can lead to strange behavior since the stop method is automatically called by Spring Boot.

[mikebell90]

My assumption is the logic was indeed "one last time" or metrics would be lost. What's wrong with this? I suspect you could subclass and override close. And track with AtomicBoolean.compareAndSet

[ummels]

I've opened #4246 for this issue. I've just added a check whether the reporter has been started.