Component Cron Jobs Definitions

A component can define a job to be executed recurrently.

As other kind of Mantra assets, you have two ways to define a cron job in a component: using the hook "Cron" of implicity in a file.

Defining a cron using the hook "Cron"

You just need to add the hook "Cron" like this:

Mantra.Hooks("mycomponent")
    .Cron({
        CronConfig: "standard cron configuration",
        CronHandler: async () => {}
    });

Where:

• CronConfig: standard cron configuration based on Linux crontab, for instance: "0/1 * * * * *"
• CronHandler: asyncronous function to be called to perform some action periodically according to the cron configruration.

Defining a cron implicity

The same than above, can be indicated in a file named as "cron.<componentname>.js" that should be inside "/controllers" folder of the component.

In this case, the properties of the hook "Cron" are indicated as properties to be exported by that module:

• <cron name>: name of the cron job.
• <cron name>_config: cron configuration

Here there's an example:

module.exports = {
    newtick_config: "*/1 * * * * *",
    newtick : async ( ) => {
        const Mantra = global.Mantra.MantraAPIFactory();

        await Mantra.LogInfo( `New tick! at ${new Date().toISOString() }`)
    }
}

Cron aliases

Cron configuration can be set by some Mantra aliases, easy to understand and write.

Are these ones:

• "1s": equivalent to "*/1 * * * * *"
• "5s": : equivalent to "*/5 * * * * *"
• "30s": : equivalent to "*/30 * * * * *"
• "1m": : equivalent to "0 */1 * * * *"
• "5m": equivalent to "0 */5 * * * *"
• "30m": equivalent to "0 */30 * * * *"
• "1h": equivalent to "0 0 */1 * * *"
• "5h": equivalent to "0 0 */5 * * *"
• "1d": equivalent to "0 0 0 */1 * *"

For example, to define a cron to be called efery five minutes:

module.exports = {
    newtick_config: "5m",
    newtick : async ( ) => {
        const Mantra = global.Mantra.MantraAPIFactory();

        await Mantra.LogInfo( `New tick! at ${new Date().toISOString() }`)
    }
}

Cron config by component property

Another method to define the configuration of the cron, consists of use a property of the component.

A component can have any number of properties, defined at "defaultconfig" value at mantra.json of the component. These default properties can be overwritten at mantraconfig.json project file at "ComponentsConfig" section.

Read about component configuration.

Mantra check the value of the cron configuration in this order:

• Checks if it is a valid crontab value.
• If not, checks if it is an alias as described above.
• If not, checks if it is a component configuration propert.

In the example:

module.exports = {
    newtick_config: "tickcronconfig",
    newtick : async ( ) => {
        const Mantra = global.Mantra.MantraAPIFactory();

        await Mantra.LogInfo( `New tick! at ${new Date().toISOString() }`)
    }
}

, Mantra expects to find the property configuration "tickcronconfig" at the component configuration.

Mantra API instance in cron jobs

Mantra creates itself a Mantra API instance en each interaction with the compoments.

However, due to the nature of cron jobs, if the cron handler needs to get a Mantra API instance, the it should create it itself with:

const Mantra = global.Mantra.MantraAPIFactory();

List crons defined by a component

You can get the list of crons defined by a component with show-crons Mantra command:

$ mantrad show-crons <component name>

This is useful to verify that you have defined you crons well.

To learn by example, go to Mantra demos and components sections of Mantra site.