Simple CLI integration

[splitice]

Thank you for your hard work. Been reading through this and the few other implementations of distributed locking systems. A uniquely simple design in this case. Effectively you take the lock for (default) 10 seconds and keep renewing it preventing expiration (every 3 seconds). Simple design and K8S services while they can be a bit jittery should be reliable on that scale. Competition between acquiring workers being handled by a race to insert.

I don't do anything normally with golang so correct me if I am wrong.

Any chance that an (example?) of a CLI application could be developed that could be usable from scripting languages? This would make your work accessible from sh/bash (or any other scripting language supporting shell commands - i.e most of them)? I suspect even languages like PHP and python could make use of it via proc open type interfaces.

My thoughts regarding API:

#!/bin/bash

keyname="our key"

# take lock $keyname
k8lock $keyname &
lockpid=$!

do_stuff

# signal for clean exit
kill -sHUP $lockpid
wait $lockpid

distlock should also monitor it's parent pid for exit (and release the lock accordingly i.e in case of crash).

In C I would do this with a signal handler on SIGHUP and use PR_SET_PDEATHSIG to ensure a SIGHUP is received on parent death for that graceful cleanup.

[distorhead]

Hi, thanks for your feedback!

I think it would be great to implement such CLI app. Flock unix util could be used as another example CLI.

The only thing: it is important to implement on-lost-lease handler for such CLI command, in the simple/universal case this handler should just crash whole script immediately, in some cases this handler could revert back introduced changes then crash (depends on an application logic).

[splitice]

I guess if the lock cli exits early thats a lost lock. Although that really shouldnt be possible and many CLI applications are not easily able to check the statuses of their children (and shouldnt be expected to). I don't think the child sending signals to the parent is a good idea (e.g to interrupt / terminate it) at-least not by default.

I'm pretty much thinking of usage like a simple distributed flock 👍

[cwarden]

Here's a simple cli I built using lockgate: https://github.com/octoberswimmer/deploylock