event.Op&fsnotify.Create == fsnotify.Create

if we trigger a reload when create signal is received wouldn't we have a race condition where the file is still being rewritten and we start reloading? it seems that when CREATE is received there will be a CLOSE_WRITE event later on as well so we may just wait for CLOSE_WRITE?

also if the file is moved from another location to the location that we're monitoring we should check IN_MOVED_TO event as well, right? #Closed

1. There is a potential timing issue where if the cert file is created and then written to that we could potentially miss the CLOSE_WRITE event thus reloading with the non-written or partial-written cert/key. I think the one way we can fix this is with a debounce timer such that we check for incoming events in the next couple of seconds and we use the latest event as the event to act on. We can't just use CLOSE_WRITE as the only option as there are certain operations where only CREATE is triggered but not CLOSE_WRITE such as when you execute "mv" from another location to the monitored directory.

2. CREATE/CLOSE_WRITE are triggered when we move /copy/write to the cert files in the monitored directory.

for mv it's actually rename() syscall invoked which triggers IN_MOVED_TO event:

kema2@KEMA2-SL1:/mnt/c/Users/kema2$ strace mv temp1.csv.bak temp1.csv
renameat(AT_FDCWD, "temp1.csv.bak", AT_FDCWD, "temp1.csv") = 0

https://man7.org/linux/man-pages/man7/inotify.7.html

Suppose an application is watching the directories dir1 and dir2,
and the file dir1/myfile. The following examples show some events
that may be generated.

       link("dir1/myfile", "dir2/new");
              Generates an IN_ATTRIB event for myfile and an
              IN_CREATE event for dir2.

       rename("dir1/myfile", "dir2/myfile");
              Generates an IN_MOVED_FROM event for dir1, an
              IN_MOVED_TO event for dir2, and an IN_MOVE_SELF event
              for myfile.  The IN_MOVED_FROM and IN_MOVED_TO events
              will have the same cookie value.

cp should trigger CREATE and CLOSE_WRITE IIUC.

btw I don't think we'll ever miss some notification as long as we consume the event as fast as possible.

You are right, fsnotify however uses "CREATE" for both CREATE and IN_MOVED_TO calls: https://github.com/fsnotify/fsnotify/blob/c2828203cd70a50dcccfb2761f8b1f8ceef9a8e9/inotify.go#L321

if mask&unix.IN_CREATE == unix.IN_CREATE || mask&unix.IN_MOVED_TO == unix.IN_MOVED_TO {
	e.Op |= Create
}

Which explains why when I move a file to the monitored directory we still only just see the create event,

Added code to distinguish between between CREATE and IN_MOVED_TO events such that we support reloading on IN_MOVED_TO events and CLOSE_WRITE events.

Added appropriate UT as wel..