RFR: 8293067: (fs) Implement WatchService using system library (macOS)

[Michael Hall]

> On Sep 12, 2022, at 3:17 AM, Maxim Kartashev <mkartashev at openjdk.org> wrote:
> 
> On Thu, 8 Sep 2022 14:49:52 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:
> 
>>>> In our CI system `test/jdk/java/nio/file/WatchService/Move.java` appears to time out consistently, although I have not seen it happen on my local machine.
>>> 
>>> Can you provide the `.jtr` file, please? I haven't seen the test hang, but by inserting different delays different systems can expose synchronization issues, of course.
>> 
>>> Can you provide the `.jtr` file, please? I haven't seen the test hang, but by inserting different delays different systems can expose synchronization issues, of course.
>> 
>> I can't give the whole .jtr file due to internal content, but here are some excerpts.
> 
> @bplb Thanks for the log. It's really strange, though, that there is nothing from `System.out` because the test itself logs intensively even before any `WatchService` code is executed. Also, AFAIK timeouts trigger thread dump, which would be quite helpful. Are you not at liberty to share those as well?
> 
> -------------
> 
> PR: https://git.openjdk.org/jdk/pull/10140

Excuse my unofficial interest. But I had attempted a kqueue based OS/X watch service sometime back that failed, so it’s interesting to see one working.
Mine would stop receiving kernel events running the LotsOfEvents test. It never got past that.
Checking LotsOfEvents out of curiosity I notice it’s millis timing is…
overflow elapsed 32200
queuing elapsed 24292 

While again the Move test runs in like…
move subtree elapsed 1048
move file elapsed 2018

So why would tests consistently time out in Move runs when LotsOfEvents takes longer for me? I am of course unfamiliar with the JDK testing but this seems odd.