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Cron jobs in mist-cloud

In order to run code at fixed intervals in mist-cloud we can use cron jobs. A mist cron job is a mechanism that can be configured to post custom events to the rapids at fixed times. For example, every 5 minutes (*/5 * * * *), or the last weekday of every month (0 0 L * *).

Although the complete syntax of cron expressions is out of the scope of this tutorial, our syntax of cron has 5-6 elements:

• Seconds (optional)
• Minutes
• Hours
• Day of month, where L is last weekday
• Month, where 1 is January
• Day of week, where 1 is Monday

Example cron expressions:

• Every 5 minutes: */5 * * * *
• At midnight the last weekday of every month: 0 0 L * *
• Noon Monday through Friday: 0 12 * * 1-5
• 8pm on the 3rd and 23rd of every month: 0 20 3,23 * *

To set up a cron job in mist-cloud simply use the command:

mist cron [name] --expr "[cron expression]" --event [event to post]

Using the 5 minute expression from above it cloud look like this:

mist cron hello --expr "*/5 * * * *"

Meaning, create a cron job called hello, that posts hello every 5 minutes.

⚠ Things to note:

• If event is omitted the name is used.
• A cron event is posted without payload, and replies have no effect.
• Cron jobs are organization wide.
• To prevent accidental updates mist-cli requires you to specify --overwrite if you want to modify an existing cron job.

You can delete a cron job by specifying an empty expression (""). And finally you can list your current cron jobs with the command:

mist list-crons