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nim-schedules

A Nim scheduler library that lets you kick off jobs at regular intervals.

Read the documentation.

Features:

  • Simple to use API for scheduling jobs.
  • Support scheduling both async and sync procs.
  • Lightweight and zero dependencies.

Getting Started

$ nimble install schedules

Usage

# File: scheduleExample.nim
import schedules, times, asyncdispatch

schedules:
  every(seconds=10, id="tick"):
    echo("tick", now())

  every(seconds=10, id="atick", async=true):
    echo("tick", now())
    await sleepAsync(3000)
  1. Schedule thread proc every 10 seconds.
  2. Schedule async proc every 10 seconds.

Run:

nim c --threads:on -r scheduleExample.nim

Note:

  • Don't forget --threads:on when compiling your application.
  • The library schedules all jobs at a regular interval, but it'll be impacted by your system load.

Advance Usages

Cron

You can use cron to schedule jobs using cron-like syntax.

import schedules, times, asyncdispatch

schedules:
  cron(minute="*/1", hour="*", day_of_month="*", month="*", day_of_week="*", id="tick"):
    echo("tick", now())

  cron(minute="*/1", hour="*", day_of_month="*", month="*", day_of_week="*", id="atick", async=true):
    echo("tick", now())
    await sleepAsync(3000)
  1. Schedule thread proc every minute.
  2. Schedule async proc every minute.

Throttling

By default, only one instance of the job is to be scheduled at the same time. If a job hasn't finished but the next run time has come, the next job will not be scheduled.

You can allow more instances by specifying throttle=. For example:

import schedules, times, asyncdispatch, os

schedules:
  every(seconds=1, id="tick", throttle=2):
    echo("tick", now())
    sleep(2000)

  every(seconds=1, id="async tick", async=true, throttle=2):
    echo("async tick", now())
    await sleepAsync(4000)

Customize Scheduler

Sometimes, you want to run the scheduler in parallel with other libraries. In this case, you can create your own scheduler by macro scheduler and start it later.

Below is an example of co-exist jester and nim-schedules in one process.

import times, asyncdispatch, schedules, jester

scheduler mySched:
  every(seconds=1, id="sync tick"):
    echo("sync tick, seconds=1 ", now())

router myRouter:
  get "/":
    resp "It's alive!"

proc main():
  # start schedules
  asyncCheck mySched.start()

  # start jester
  let port = paramStr(1).parseInt().Port
  let settings = newSettings(port=port)
  var jester = initJester(myrouter, settings=settings)

  # run
  jester.serve()

when isMainModule:
  main()

Set Start Time and End Time

You can limit the schedules running in a designated range of time by specifying startTime and endTime.

For example,

import schedules, times, asyncdispatch, os

scheduler demoSetRange:
  every(
    seconds=1,
    id="tick",
    startTime=initDateTime(2019, 1, 1),
    endTime=now()+initDuration(seconds=10)
  ):
    echo("tick", now())

when isMainModule:
  waitFor demoSetRange.start()

Parameters startTime and endTime can be used independently. For example, you can set startTime only, or set endTime only.

ChangeLog

Released:

  • v0.2.0, 22 Jul, 2021, New feature: cron.
  • v0.1.2, 8 Jul, 2021, Bugfix: the first job schedule should be after startTime.
  • v0.1.1, update metadata.
  • v0.1.0, initial release.

License

Nim-schedules is based on MIT license.