Execute Exactly Once, Execute At Least Once? about node-redlock HOT 2 CLOSED

Hi @tomercagan,

It sounds like you have a pretty good read on how this works! The quick answer is that you'll need to store state somewhere else. Here's the longer answer:

You have a task that needs to be completed exactly once. This means that you have to account for failure at any stage of the task – even failures of the entire system (somebody might trip over the power cable). Let's break this down into its two parts:

The task must not complete MORE than once:

• If a task has been complete, we must not start it again
• If a task has been started, we must not start it again until we know whether it has completed or failed

The task must not complete LESS than once:

• If a task is created, it must start
• If a task fails:
  • In the simplest cases, we can simply restart it
  • If we keep "checkpoints" (divided it into smaller tasks) we can resume from the last complete sub-task
  • If the task has side effects, we may need to revert and re-run, etc

There's a lot of other conditions/scenarios I could add above, but this hopefully illustrates the kinds of use case you have. In this scenario, redlock is only concerned with the problem in bold. While it's a very good solution to that problem, it doesn't provide much for addressing the other problems.

More generically, it's concerned with ensuring exclusivity in a distributed environment. Hopefully that helps – and free to follow up with more questions!

Cheers,
Mike

from node-redlock.

Hi @tomercagan,

I'm going to close this issue. Please feel free to reopen if you have further questions.

from node-redlock.