Any interest in WatchService based on MacOS FSEvents?

[Laurence Cable]

On 8/29/22 11:50 PM, Maxim Kartashev wrote:
> WatchService on MacOS is still implemented by the generic 
> PollingWatchService, which continuously re-scans the directory 
> consuming CPU, introduces large latencies to the generated 
> WatchEvent's, and misses changes that occur faster than the re-scan 
> interval. At the same time, there are two technologies available on 
> the platform to receive the necessary information from the OS similar 
> to what is available on Windows and Linux: Kernel Queues and File 
> System Events, the latter being more suitable for implementing the 
> WatchServie functionality.
>
> There are several stand-alone implementations out there that utilize 
> one or the other (or even both), which suggests that demand exists for 
> WatchService on MacOS to be more responsive and less resource-hungry.
>
> If the community is interested in getting this functionality in 
> OpenJDK proper, I'd be happy to contribute code that was developed, 
> tested, and used at JetBrains for around half a year. It is based on 
> FSEvents, supports the FILE_TREE modifier (recursive directory watch), 
> and does not do any excessive I/O except the necessary minimum.
>

totally!

> References
> * WatchService interface
>   - 
> https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/nio/file/WatchService.html
> * PollingWatchService source code
>   - 
> https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/sun/nio/fs/PollingWatchService.java
> * File System Events
>   - 
> https://developer.apple.com/documentation/coreservices/file_system_events?language=objc
> * Kernel Queues
>   - 
> https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/FSEvents_ProgGuide/KernelQueues/KernelQueues.html