Azure Functions Timer Trigger Bindings

The Timer trigger allows you to run a Function at regular intervals. This is useful for background tasks, scheduled jobs, or periodic data processing.

Timer Trigger Configuration

The Timer trigger is configured using a JSON object in your function.json file. The primary property is schedule, which accepts a CRON expression.

CRON Expressions

CRON expressions are strings that define a schedule. They consist of six fields:

Special characters include:

• *: Wildcard, matches any value.
• ,: Separator, allows multiple values.
• -: Range, specifies a range of values.
• /: Step, specifies a step value.

Example CRON Expressions

• * * * * * *: Runs every minute.
• 0 * * * * *: Runs at the beginning of every hour.
• 0 0 * * * *: Runs at midnight every day.
• 0 0 1 * * *: Runs at midnight on the first day of every month.
• 0 0 0 1 1 *: Runs at midnight on January 1st of every year.

Function.json Configuration

Here's an example of how to configure a Timer trigger in your function.json:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "name": "mytimer",
      "type": "timerTrigger",
      "direction": "in",
      "schedule": "0 */5 * * * *"
    }
  ]
}
            

This configuration will trigger the function every 5 minutes.

Timer Information

When the Timer trigger fires, it passes a TimerInfo object to your function. This object contains information about the trigger, such as:

• isPastDue: A boolean indicating if the trigger missed a schedule due to system downtime.
• next: The scheduled time of the next execution.
• prev: The scheduled time of the previous execution.
• nextFromEnd: The time of the next execution, measured from the end of the current invocation.

Programming Language Examples

Python

import datetime
import logging

import azure.functions as func

def main(mytimer: func.TimerRequest) -> None:
    utc_timestamp = datetime.datetime.utcnow().isoformat()

    if mytimer.past_due:
        logging.info('The timer is past due!')

    logging.info('Python timer trigger function executed at: %s', utc_timestamp)
    logging.info('Next timer schedule is: %s', mytimer.next)
            

C#

using System;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using Microsoft.Extensions.Logging;

namespace Company.Function
{
    public static class TimerTriggerCSharp
    {
        [FunctionName("TimerTriggerCSharp")]
        public static void Run([TimerTrigger("*/5 * * * * *")]TimerInfo myTimer, ILogger log)
        {
            log.LogInformation($"C# Timer trigger function executed at: {DateTime.UtcNow}");

            if (myTimer.IsPastDue)
            {
                log.LogInformation("Timer is past due!");
            }

            log.LogInformation($"Next timer schedule: {myTimer.ScheduleStatus.Next}");
        }
    }
}
            

JavaScript

module.exports = async function (context, myTimer) {
    const timeStamp = new Date().toISOString();

    if (myTimer.isPastDue) {
        context.log('JavaScript timer trigger function is past due!');
    }
    context.log('JavaScript timer trigger function executed at!', timeStamp);
    context.log('Next timer schedule is: ', myTimer.next);
};
            

Timeouts and Delays

The Timer trigger is designed for running tasks at intervals, not for long-running operations within a single invocation. If your task takes longer than the function app's timeout, it may be terminated. For long-running tasks, consider using other Azure services like Azure Logic Apps or Azure Batch.

Troubleshooting

• Missed Schedules: If you see isPastDue is true, it means your function app may have been unavailable or the function itself was taking too long to complete.
• Incorrect Timing: Double-check your CRON expression and ensure it's configured for UTC.
• Function App Uptime: Ensure your Function App is running and scaled appropriately to handle the scheduled triggers.