Node & Session aware locking

[sam-ulrich1]

I am looking at implementing a node and session aware version of this lib. Would you be interested in a PR instead?

Goal:
In the case that a node is improperly terminated, deadlocks on the fs can be detected and automatically repaired at runtime.

Changes:

• Lock contains an id that is unique to each node but persists across many runs (sessions)
• Lock contains an id that is unique to the current session (maybe nanos of start)
• Lock will auto detect dead locks that exist from a prior session of the same node and remove the deadlock

[sam-ulrich1]

@chrisgilmerproj I completed my modifications. Are you interested in a PR?

[chrisgilmerproj]

Yes please!

[sam-ulrich1]

Great to hear! I'll get it over by the end of the day

[sam-ulrich1]

So I private forked it and made the mods here https://github.com/Gage-Technologies/safelock

I'm going to personally fork it and copy the changes so I can PR easily

[sam-ulrich1]

@chrisgilmerproj not sure if you saw it but here's the pr #63
No worries if you're just busy!

[sam-ulrich1]

@chrisgilmerproj I found a bug in the latest merge. The usage of newline for separation can have collisions with the little endian endcoded session ids. It's common enough that after about 4 million file locks I've found 50k deadlocks. I've traded out the separator for __::__ in our repo. I can send another PR soon if you'd like

[chrisgilmerproj]

No problem @sam-ulrich1 . Send a PR and I'll approve it.

[sam-ulrich1]

@chrisgilmerproj #72

[chrisgilmerproj]

Reviewed and merged!