https://github.com/noteed/minicron

Simple cron-like tool
https://github.com/noteed/minicron

Last synced: about 2 months ago
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Simple cron-like tool

• Host: GitHub
• URL: https://github.com/noteed/minicron
• Owner: noteed
• License: other
• Created: 2014-08-06T01:01:36.000Z (over 10 years ago)
• Default Branch: main
• Last Pushed: 2024-03-07T11:27:56.000Z (10 months ago)
• Last Synced: 2024-03-07T12:42:05.662Z (10 months ago)
• Language: Nix
• Size: 19.5 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Minicron

Minicron runs tasks.

## Design

There is a wakeup service, and then the tasks service.

The wakeup service simply sends scheduled wakeup messages. It maintains a

single pending wakeup, which can be replaced by another scheduled wakeup.

The tasks service maintains the set of tasks to be run. When it receives a

wakeup message, it tries to run tasks. It schedules wakeups using the wakeup

service. It can do so either by returning a value after running a task (when it

already knows another task will need a wakeup), or by requesting explicitely a

new wakeup (e.g. when it is notified by another service that a new task has

been added).

In the wakeup service, there are two threads. The main thread spawns the second

thread. The second thread sleeps the requested amount of time, then notifies

the main thread it is time to send a wakeup. The main thread also listens for

requests for a new wakeup value.

## Usage

The simple usage is to write a small Haskell script that creates a set of

tasks, then call `System.Cron.Mini.cron`. This will result in a program that

executes the tasks, until the set of tasks is empty (which might never be the

case if e.g. a task repeats endlessy).

The second usage is to write a client thread that will implement the tasks

service and communicate with the wakeup service. This makes it possible to

dynamically change the set of tasks and continue to run even if it becomes

empty. For instance the set of tasks can be recorded in a database, and the

client thread will wait for a record to appear before requesting a wakeup.