New Cron Scheduling!

[ndortega]

Hello everyone,

I'm finally at a place where I'm happy with the cron parser & scheduler, which means it will be getting published sometime within the next week or two. I added some logging to the cron and & repeat task modules to see which tasks & cron jobs were registered on startup.

What do you guys think of the format?

On a side note, here are a couple of different ways you can use the new cron scheduling feature taken from the demo project file: https://github.com/ndortega/Oxygen.jl/blob/feature/cron-expressions/demo/crondemo.jl

Examples

When making the cron module, I used the spring docs as a guide and made sure that my implementation matched their design description.

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/scheduling/support/CronExpression.html

"0 0 * * * *" = the top of every hour of every day.
"*/10 * * * * *" = every ten seconds.
"0 0 8-10 * * *" = 8, 9 and 10 o'clock of every day.
"0 0 6,19 * * *" = 6:00 AM and 7:00 PM every day.
"0 0/30 8-10 * * *" = 8:00, 8:30, 9:00, 9:30, 10:00 and 10:30 every day.
"0 0 9-17 * * MON-FRI" = on the hour nine-to-five weekdays
"0 0 0 25 12 ?" = every Christmas Day at midnight
"0 0 0 L * *" = last day of the month at midnight
"0 0 0 L-3 * *" = third-to-last day of the month at midnight
"0 0 0 1W * *" = first weekday of the month at midnight
"0 0 0 LW * *" = last weekday of the month at midnight
"0 0 0 * * 5L" = last Friday of the month at midnight
"0 0 0 * * THUL" = last Thursday of the month at midnight
"0 0 0 ? * 5#2" = the second Friday in the month at midnight
"0 0 0 ? * MON#1" = the first Monday in the month at midnight

How the cron format works

There are six fields that can go into a cron expression in oxygen. Generally, most cron schedulers don't support seconds, but I felt it could be useful and decided to add it in.

seconds, minutes, hours, day of month, month, day of week

All trailing fields are optional, which you can see below where I only pass in the seconds expression. So if you only need to set the first 2 fields, then you can leave out the rest of the fields and Oxygen will assume you passed an "*" character that matches anything.

Using the @cron macro directly on a custom function

@cron "*/2" function()
    println("every 2 seconds")
end

# Here's an example of a more complex expression
@cron "0 0 0 ? * MON#1" function()
    println("The first Monday in the month at midnight")
end

Pase the expression directly to a router

# call this endpoint every 11 seconds
@get router("/increment", cron="*/11") function()
    global value += 1
    return value
end

Endpoints can inherit cron expressions & override them just like the other properties in the router

# all endpoints will inherit this cron expression
pingpong = router("/pingpong", cron="*/3"). # call this every 3 seconds

@get pingpong("/ping") function() # this would get called every 3 seconds
    println("ping")
    return "ping"
end

# here we override the inherited cron expression
@get pingpong("/pong", cron="*/7") function() # call this every 7 seconds
    println("pong")
    return "pong"
end

[ndortega]

@the-noble-argon

Sorry about the long wait, it's almost here! Let me know what you think