utils/fslock needs to DIAF

[Tim Penhey]

Hi folks,

The fslock was a mistake that I added to the codebase some time back. It
provided an overly simplistic solution to a more complex problem.

Really the filesystem shouldn't be used as a locking mechanism.

Most of the code that exists for the fslock now is working around its
deficiencies. Instead we should be looking for a better replacement.

Some "features" that were added to fslock were added to work around the
issue that the lock did not die with the process that created it, so
some mechanism was needed to determine whether the lock should be broken
or not.

What we really need is a good OS agnostic abstraction that provides the
ability to create a "named" lock, acquire the lock, release the lock,
and make sure that the lock dies when the process dies, so another
process that is waiting can acquire the lock. This way no "BreakLock"
functionality is required, nor do we need to try and do think like
remember which process owns the lock.

So...

We have three current operating systems we need to support:

Linux - Ubuntu and CentOS
MacOS - client only - bit the CLI uses a lock for the local cache
Windows

For Linux, and possibly MacOS, flock is a possibility, but can we do
better? Is there something that is better suited?

For Windows, while you can create global semaphores or mutex instances,
I'm not sure of entities that die with the process. Can people recommend
solutions?

Cheers,
Tim