cdule

cdule (pronounce as Schedule)

Golang based scheduler library with database support. Users could use any database which is supported by gorm.io.

To Download the cdule library

go get github.com/deepaksinghvi/cdule

Usage Instruction

In order to schedule jobs with cdule, user needs to

1. Configure persistence
2. Implement cdule.Job Interface &
3. Schedule job with required cron expression.

Job will be persisted in the jobs table.
Next execution would be persisted in schedules tables.
Job history would be persisted and maintained in job_histories table.

Configuration

User needs to create a resources/config.yml in their project home directory with the followling keys

• cduletype
• dburl
• cduleconsistency

cduletype is used to specify whether it is an In-Memory or Database based configuration. Possible values are DATABASE and MEMORY. dburl is the database connection url. cduleconsistency is for reserved for future usage.

config.yml for postgressql based configuration

cduletype: DATABASE
dburl: postgres://cduleuser:cdulepassword@localhost:5432/cdule?sslmode=disable
cduleconsistency: AT_MOST_ONCE

config.yml for sqlite based in-memory configuration

cduletype: MEMORY
dburl: /Users/dsinghvi/sqlite.db
cduleconsistency: AT_MOST_ONCE

Job Interface Implementation

var testJobData map[string]string

type TestJob struct {
	Job cdule.Job
}

func (m TestJob) Execute(jobData map[string]string) {
	log.Info("In TestJob")
	for k, v := range jobData {
		valNum, err := strconv.Atoi(v)
		if nil == err {
			jobData[k] = strconv.Itoa(valNum + 1)
		} else {
			log.Error(err)
		}

	}
	testJobData = jobData
}

func (m TestJob) JobName() string {
	return "job.TestJob"
}

func (m TestJob) GetJobData() map[string]string {
	return testJobData
}

Schedule a Job

It is expected that testJob will be Executed five times, once for every minute and program will exit. TestJob jobData map holds the data in the format of map[string]string where gets stored for every execution and gets updated as the next counter value on Execute() method call.

cdule := cdule.Cdule{}
cdule.NewCdule()
testJob := TestJob{}
jobData := make(map[string]string)
jobData["one"] = "1"
jobData["two"] = "2"
jobData["three"] = "3"
cdule.NewJob(&testJob, jobData).Build(utils.EveryMinute)

time.Sleep(5 * time.Minute)
cdule.StopWatcher()

Demo Project

This demo describes how cdule library can be used.

https://github.com/deepaksinghvi/cduledemo

Database Schema

For the sample app, postgresql is used but users can use any db which is supported by gorm.io.

DB Tables

• jobs : To store unique jobs.
• job_histories : To store job history with status as result.
• schedules : To store schedule for every next run.
• workers : To store the worker nodes and their health check.

Sample Cron

Users can use the pre-defined crons or use their own which are the standard cron expression

EveryMinute              = "0 * * ? * *"
EveryEvenMinute          = "0 */2 * ? * *"
EveryUnEvenMinute        = "0 1/2 * ? * *"
EveryTwoMinutes          = "0 */2 * ? * *"
EveryHourAtMin153045     = "0 15,30,45 * ? * *"
EveryHour                = "0 0 * ? * *"
EveryEvenHour            = "0 0 0/2 ? * *"
EveryUnEvenHour          = "0 0 1/2 ? * *"
EveryThreeHours          = "0 0 */3 ? * *"
EveryTwelveHours         = "0 0 */12 ? * *"
EveryDayAtMidNight       = "0 0 0 * * ?"
EveryDayAtOneAM          = "0 0 1 * * ?"
EveryDayAtSixAM          = "0 0 6 * * ?"
EverySundayAtNoon        = "0 0 12 ? * "
EveryMondayAtNoon        = "0 0 12 ? *"
EveryWeekDayAtNoon       = "0 0 12 ? * MON-FRI"
EveryWeekEndAtNoon       = "0 0 12 ? * SUN,SAT"
EveryMonthOnFirstAtNoon  = "0 0 12 1 * ?"
EveryMonthOnSecondAtNoon = "0 0 12 2 * ?"

This library is built using

• Cron parser using the library robfig/cron
• ORM usign the library gorm.io