Crontab-like Kotlin Coroutines launching scheduler

krontab

Library was created to give oppotunity to launch some things from time to time according to some schedule in runtime of applications.

How to use

There are several ways to configure and use this library:

• From some string
• From builder

Anyway, to start some action from time to time you will need to use one of extensions/functions:

val kronScheduler = /* creating of KronScheduler instance */;

kronScheuler.doWhile {
    // some action
    true // true - repeat on next time
}

Including in project

If you want to include krontab in your project, just add next line to your dependencies part:

implementation "com.insanusmokrassar:krontab:$krontab_version"

Next version is the latest currently for the library:

For old version of Gradle, instead of implementation word developers must use compile.

Config from string

Developers can use more simple way to configure repeat times is string. String configuring like a crontab, but with a little bit different meanings:

/-------- Seconds
| /------ Minutes
| | /---- Hours
| | | /-- Days of months
| | | | / Months
| | | | |
* * * * *

It is different with original crontab syntax for the reason, that expected that in practice developers will use seconds and minutes with more probability than months (for example). In fact, developers will use something like:

doWhile("/5 * * * *") {
    println("Called")
    true // true - repeat on next time
}

Or more version:

doInfinity("/5 * * * *") {
    println("Called")
}

Both of examples will print Called message every five seconds.

Config via builder

Also this library currently supports DSL for creating the same goals:

val kronScheduler = buildSchedule {
    seconds {
        from (0) every 5
    }
}
kronScheduler.doWhile {
    println("Called")
    true // true - repeat on next time
}

Or

val kronScheduler = buildSchedule {
    seconds {
        0 every 5
    }
}
kronScheduler.doWhile {
    println("Called")
    true // true - repeat on next time
}

Or

val kronScheduler = buildSchedule {
    seconds {
        0 every 5
    }
}
kronScheduler.doInfinity {
    println("Called")
}

All of these examples will do the same things: print Called message every five seconds.

KronScheduler as a Flow

Any KronSchedulercan e converted to a Flow<DateTime using extension asFlow:

val kronScheduler = buildSchedule {
    seconds {
        0 every 1
    }
}

val flow = kronScheduler.asFlow()

So, in this case any operations related to flow are available and it is expected that they will work correctly. For example, it is possible to use this flow with takeWhile:

flow.takeWhile {
    condition()
}.collect {
    action()
}