Timer trigger for Azure Functions

This article explains how to work with timer triggers in Azure Functions. A timer trigger lets you run a function on a schedule.

This is reference information for Azure Functions developers. If you're new to Azure Functions, start with the following resources:

• Azure Functions developer reference.

• Azure Functions triggers and bindings concepts..

• Code and test Azure Functions locally..

For information on how to manually run a timer-triggered function, see Manually run a non HTTP-triggered function.

Support for this binding is automatically provided in all development environments. You don't have to manually install the package or register the extension.

Source code for the timer extension package is in the azure-webjobs-sdk-extensions GitHub repository.

Example

        //<docsnippet_fixed_delay_retry_example>
        [Function(nameof(TimerFunction))]
        [FixedDelayRetry(5, "00:00:10")]
        public static void Run([TimerTrigger("0 */5 * * * *")] TimerInfo timerInfo,
            FunctionContext context)
        {
            var logger = context.GetLogger(nameof(TimerFunction));

[FunctionName("TimerTriggerCSharp")]
public static void Run([TimerTrigger("0 */5 * * * *")]TimerInfo myTimer, ILogger log)
{
    if (myTimer.IsPastDue)
    {
        log.LogInformation("Timer is running late!");
    }
    log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
}

@FunctionName("keepAlive")
public void keepAlive(
  @TimerTrigger(name = "keepAliveTrigger", schedule = "0 */5 * * * *") String timerInfo,
      ExecutionContext context
 ) {
     // timeInfo is a JSON string, you can deserialize it to an object using your favorite JSON library
     context.getLogger().info("Timer is triggered: " + timerInfo);
}

import datetime
import logging
import azure.functions as func

app = func.FunctionApp()

@app.function_name(name="mytimer")
@app.timer_trigger(schedule="0 */5 * * * *", 
              arg_name="mytimer",
              run_on_startup=True) 
def test_function(mytimer: func.TimerRequest) -> None:
    utc_timestamp = datetime.datetime.utcnow().replace(
        tzinfo=datetime.timezone.utc).isoformat()
    if mytimer.past_due:
        logging.info('The timer is past due!')
    logging.info('Python timer trigger function ran at %s', utc_timestamp)

{
    "schedule": "0 */5 * * * *",
    "name": "myTimer",
    "type": "timerTrigger",
    "direction": "in"
}

import datetime
import logging

import azure.functions as func


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

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

    logging.info('Python timer trigger function ran at %s', utc_timestamp)

import { app, InvocationContext, Timer } from '@azure/functions';

export async function timerTrigger1(myTimer: Timer, context: InvocationContext): Promise<void> {
    context.log('Timer function processed request.');
}

app.timer('timerTrigger1', {
    schedule: '0 */5 * * * *',
    handler: timerTrigger1,
});

const { app } = require('@azure/functions');

app.timer('timerTrigger1', {
    schedule: '0 */5 * * * *',
    handler: (myTimer, context) => {
        context.log('Timer function processed request.');
    },
});

{
    "schedule": "0 */5 * * * *",
    "name": "myTimer",
    "type": "timerTrigger",
    "direction": "in"
}

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

    if (myTimer.isPastDue)
    {
        context.log('Node is running late!');
    }
    context.log('Node timer trigger function ran!', timeStamp);   
};

{
    "schedule": "0 */5 * * * *",
    "name": "myTimer",
    "type": "timerTrigger",
    "direction": "in"
}

# Input bindings are passed in via param block.
param($myTimer)

# Get the current universal time in the default string format.
$currentUTCtime = (Get-Date).ToUniversalTime()

# The 'IsPastDue' property is 'true' when the current function invocation is later than scheduled.
if ($myTimer.IsPastDue) {
    Write-Host "PowerShell timer is running late!"
}

# Write an information log with the current time.
Write-Host "PowerShell timer trigger function ran! TIME: $currentUTCtime"

When you're developing locally, add your application settings in the local.settings.json file in the Values collection.

See the Example section for complete examples.

Usage

When a timer trigger function is invoked, a timer object is passed into the function. The following JSON is an example representation of the timer object.

{
    "Schedule":{
        "AdjustForDST": true
    },
    "ScheduleStatus": {
        "Last":"2016-10-04T10:15:00+00:00",
        "LastUpdated":"2016-10-04T10:16:00+00:00",
        "Next":"2016-10-04T10:20:00+00:00"
    },
    "IsPastDue":false
}

{
    "schedule":{
        "adjustForDST": true
    },
    "scheduleStatus": {
        "last":"2016-10-04T10:15:00+00:00",
        "lastUpdated":"2016-10-04T10:16:00+00:00",
        "next":"2016-10-04T10:20:00+00:00"
    },
    "isPastDue":false
}

The isPastDue property is true when the current function invocation is later than scheduled. For example, a function app restart might cause an invocation to be missed.

NCRONTAB expressions

Azure Functions uses the NCronTab library to interpret NCRONTAB expressions. An NCRONTAB expression is similar to a CRON expression except that it includes an additional sixth field at the beginning to use for time precision in seconds:

{second} {minute} {hour} {day} {month} {day-of-week}

Each field can have one of the following types of values:

To specify months or days you can use numeric values, names, or abbreviations of names:

• For days, the numeric values are 0 to 6 where 0 starts with Sunday.
• Names are in English. For example: Monday, January.
• Names are case-insensitive.
• Names can be abbreviated. Three letters is the recommended abbreviation length. For example: Mon, Jan.

NCRONTAB examples

Here are some examples of NCRONTAB expressions you can use for the timer trigger in Azure Functions.

NCRONTAB time zones

The numbers in a CRON expression refer to a time and date, not a time span. For example, a 5 in the hour field refers to 5:00 AM, not every 5 hours.

The default time zone used with the CRON expressions is Coordinated Universal Time (UTC). To have your CRON expression based on another time zone, create an app setting for your function app named WEBSITE_TIME_ZONE.

The value of this setting depends on the operating system and plan on which your function app runs.

For example, Eastern Time in the US (represented by Eastern Standard Time (Windows) or America/New_York (Linux)) currently uses UTC-05:00 during standard time and UTC-04:00 during daylight time. To have a timer trigger fire at 10:00 AM Eastern Time every day, create an app setting for your function app named WEBSITE_TIME_ZONE, set the value to Eastern Standard Time (Windows) or America/New_York (Linux), and then use the following NCRONTAB expression:

"0 0 10 * * *"

When you use WEBSITE_TIME_ZONE the time is adjusted for time changes in the specific timezone, including daylight saving time and changes in standard time.

TimeSpan

A TimeSpan can be used only for a function app that runs on an App Service Plan.

Unlike a CRON expression, a TimeSpan value specifies the time interval between each function invocation. When a function completes after running longer than the specified interval, the timer immediately invokes the function again.

Expressed as a string, the TimeSpan format is hh:mm:ss when hh is less than 24. When the first two digits are 24 or greater, the format is dd:hh:mm. Here are some examples:

Scale-out

If a function app scales out to multiple instances, only a single instance of a timer-triggered function is run across all instances. It will not trigger again if there is an outstanding invocation still running.

Function apps sharing Storage

If you are sharing storage accounts across function apps that are not deployed to app service, you might need to explicitly assign host ID to each app.

You can omit the identifying value or manually set each function app's identifying configuration to a different value.

The timer trigger uses a storage lock to ensure that there is only one timer instance when a function app scales out to multiple instances. If two function apps share the same identifying configuration and each uses a timer trigger, only one timer runs.

Retry behavior

Unlike the queue trigger, the timer trigger doesn't retry after a function fails. When a function fails, it isn't called again until the next time on the schedule.

Manually invoke a timer trigger

The timer trigger for Azure Functions provides an HTTP webhook that can be invoked to manually trigger the function. This can be extremely useful in the following scenarios.

• Integration testing
• Slot swaps as part of a smoke test or warmup activity
• Initial deployment of a function to immediately populate a cache or lookup table in a database

Please refer to manually run a non HTTP-triggered function for details on how to manually invoke a timer triggered function.

Troubleshooting

For information about what to do when the timer trigger doesn't work as expected, see Investigating and reporting issues with timer triggered functions not firing.

Next steps