Customizing Azure timer-triggered functions CRON value

Question

We have the following scenario:

Our UI is giving the users the option of running their tasks periodically e.g. once in every hour, once in every 12 hours or once a day, etc. The backend that runs the tasks is an Azure timer-triggered function but it spawns periodically based on the configuration defined in the environment variables:

    [Function("JobRunner")]
    public Task RunAsync([TimerTrigger("%RunningCron%")] MyInfo myTimer)
    {
        _logger.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
        _logger.LogInformation($"Next timer schedule at: {myTimer.ScheduleStatus?.Next}");
        //Do something
        return Task.CompletedTask;
    }

The value of "%RunningCron% is constant, and as stated earlier it's coming from environment variables e.g. local.settings.json file, etc.

How can we make the CRON value picked up from the database where the user's choice is stored.

VenkateshDodda · Accepted Answer · 2022-04-05 07:21:21Z

0

As per your requirement, We understood that multiple users may access the UI & change their CORN expression accordingly. Using single timer trigger functions won't be the feasible solution here. we would suggest you make the changes to the application UI whenever a user tries to change the CORN expression it should create the Timer trigger function using Rest API based on that particular corn expression.

For example:

If your application is having only one timer trigger function and there were 2 users (user1, user2) who are trying to access your application by passing the dynamic corn expressions.

user1 has passed this corn expression as input 0 0 */6 * * * to schedule a particular task (job1) in the application.
user2 has passed this CORN expression 0 0 * * * 1-5 to schedule a particular job(job2) in their application.

Since you are using a single timer trigger in your application job1 scheduled by user1 will get overridden by the job2 scheduled by the user2.

answered Apr 5, 2022 at 7:21

VenkateshDodda

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1 Comment

Arash Over a year ago

Thanks for the reply. I was wondering how I can have the function created by the REST API invoke the backend's code? @VenkateshDodda-MSFT

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