A scheduler script to locally mimic Heroku's Scheduler

README.md

./bin/scheduler

A scheduler script to locally mimic Heroku's Scheduler.

You may find the script useful if

• you have a Rails app and deploy on Heroku
• during development, you need to locally run jobs at scheduled time intervals
• you use a Procfile-based app manager such as Foreman

Usage

1. Copy scheduler.sh as bin/scheduler and make it executable
2. Copy scheduler.rake to lib/tasks/
3. Add scheduler: ./bin/scheduler to your Procfile.dev

Then run the app with

foreman start -f Procfile.dev 

In addition you may do so with a script i.e bin/up

#!/bin/sh
foreman start -f Procfile.dev

scheduler.rake

# Meant to loosely mimic Heroku's Scheduler API
namespace :scheduler do
  desc "All the tasks that need to run every 10 minutes"
  task every_10_minutes: []

  desc "All the tasks that need to run every hour"
  task hourly: []

  desc "All the tasks that need to run every day"
  task daily: [
    :"task1",
    :"namespace:task1"
  ]
end

scheduler.sh

#!/usr/bin/env bash

run_task() {
  task_name=$1
  echo "Running task: $task_name"
  # The --trace flag will tell Rake to log the name of
  # each task it executes
  bundle exec rails "$task_name" --trace
}

current_minute() {
  date +%M
}

current_hour() {
  date +%H
}

main() {
  start_minute=$(current_minute)
  start_hour=$(current_hour)

  while true; do
    minutes=$(current_minute)
    hours=$(current_hour)
    echo "Checking at time: $hours:$minutes"

    # 10#$var helps avoid unwanted octal number interpolations
    if [[ $((10#$minutes % 10)) -eq $start_minute ]];then
      run_task scheduler:every_10_minutes
    fi

    if [[ $((10#$minutes)) -eq $start_minute ]];then
      run_task scheduler:hourly

      # Add 1 hour to avoid slow-down when booting the development server
      if [[ $((10#$hours)) -eq $((10#$start_hour + 1)) ]];then
        run_task scheduler:daily
      fi
    fi

    sleep 60
  done
}

main