title	description	ms.assetid	ms.topic	ms.date	ms.devlang	ms.custom	zone_pivot_groups
Timer trigger for Azure Functions	Understand how to use timer triggers in Azure Functions.	d2f013d1-f458-42ae-baf8-1810138118ac	reference	03/04/2022	csharp, java, javascript, powershell, python	devx-track-csharp, devx-track-python	programming-languages-set-functions-lang-workers

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.

[!INCLUDE intro]

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

[!INCLUDE functions-package-auto]

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

Example

::: zone pivot="programming-language-csharp"

This example shows a C# function that executes each time the minutes have a value divisible by five. For example, when the function starts at 18:55:00, the next execution is at 19:00:00. A TimerInfo object is passed to the function.

[!INCLUDE functions-bindings-csharp-intro]

In-process

[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}");
}

Isolated process

:::code language="csharp" source="~/azure-functions-dotnet-worker/samples/Extensions/Timer/TimerFunction.cs" range="12-18":::

C# Script

The following example shows a timer trigger binding in a function.json file and a C# script function that uses the binding. The function writes a log indicating whether this function invocation is due to a missed schedule occurrence. The TimerInfo object is passed into the function.

Here's the binding data in the function.json file:

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

Here's the C# script code:

public static void Run(TimerInfo myTimer, ILogger log)
{
    if (myTimer.IsPastDue)
    {
        log.LogInformation("Timer is running late!");
    }
    log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}" );  
}

::: zone-end ::: zone pivot="programming-language-java"

The following example function triggers and executes every five minutes. The @TimerTrigger annotation on the function defines the schedule using the same string format as CRON expressions.

@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);
}

::: zone-end
::: zone pivot="programming-language-javascript,programming-language-python,programming-language-powershell"

The following example shows a timer trigger binding in a function.json file and function code that uses the binding, where an instance representing the timer is passed to the function. The function writes a log indicating whether this function invocation is due to a missed schedule occurrence.

Here's the binding data in the function.json file:

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

::: zone-end
::: zone pivot="programming-language-javascript"

Here's the JavaScript code:

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);   
};

::: zone-end
::: zone pivot="programming-language-powershell"

The following is the timer function code in the run.ps1 file:

# 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"

::: zone-end
::: zone pivot="programming-language-python"

Here's the Python code, where the object passed into the function is of type azure.functions.TimerRequest object.

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)

::: zone-end
::: zone pivot="programming-language-csharp"

Attributes

Both in-process and isolated process C# libraries use the TimerTriggerAttribute attribute to define the function.

C# script instead uses a function.json configuration file.

In-process

Attribute property	Description
Schedule	A CRON expression or a TimeSpan value. A `TimeSpan` can be used only for a function app that runs on an App Service Plan. You can put the schedule expression in an app setting and set this property to the app setting name wrapped in % signs, as `%ScheduleAppSetting%`.
RunOnStartup	If `true`, the function is invoked when the runtime starts. For example, the runtime starts when the function app wakes up after going idle due to inactivity. when the function app restarts due to function changes, and when the function app scales out. Use with caution. RunOnStartup should rarely if ever be set to `true`, especially in production.
UseMonitor	Set to `true` or `false` to indicate whether the schedule should be monitored. Schedule monitoring persists schedule occurrences to aid in ensuring the schedule is maintained correctly even when function app instances restart. If not set explicitly, the default is `true` for schedules that have a recurrence interval greater than or equal to 1 minute. For schedules that trigger more than once per minute, the default is `false`.

Isolated process

Attribute property	Description
Schedule	A CRON expression or a TimeSpan value. A `TimeSpan` can be used only for a function app that runs on an App Service Plan. You can put the schedule expression in an app setting and set this property to the app setting name wrapped in % signs, as `%ScheduleAppSetting%`.
RunOnStartup	If `true`, the function is invoked when the runtime starts. For example, the runtime starts when the function app wakes up after going idle due to inactivity. when the function app restarts due to function changes, and when the function app scales out. Use with caution. RunOnStartup should rarely if ever be set to `true`, especially in production.
UseMonitor	Set to `true` or `false` to indicate whether the schedule should be monitored. Schedule monitoring persists schedule occurrences to aid in ensuring the schedule is maintained correctly even when function app instances restart. If not set explicitly, the default is `true` for schedules that have a recurrence interval greater than or equal to 1 minute. For schedules that trigger more than once per minute, the default is `false`.

C# script

C# script uses a function.json file for configuration instead of attributes.

The following table explains the binding configuration properties for C# script that you set in the function.json file.

function.json property	Description
type	Must be set to "timerTrigger". This property is set automatically when you create the trigger in the Azure portal.
direction	Must be set to "in". This property is set automatically when you create the trigger in the Azure portal.
name	The name of the variable that represents the timer object in function code.
schedule	A CRON expression or a TimeSpan value. A `TimeSpan` can be used only for a function app that runs on an App Service Plan. You can put the schedule expression in an app setting and set this property to the app setting name wrapped in % signs, as in this example: "%ScheduleAppSetting%".
runOnStartup	If `true`, the function is invoked when the runtime starts. For example, the runtime starts when the function app wakes up after going idle due to inactivity. when the function app restarts due to function changes, and when the function app scales out. Use with caution. runOnStartup should rarely if ever be set to `true`, especially in production.
useMonitor	Set to `true` or `false` to indicate whether the schedule should be monitored. Schedule monitoring persists schedule occurrences to aid in ensuring the schedule is maintained correctly even when function app instances restart. If not set explicitly, the default is `true` for schedules that have a recurrence interval greater than or equal to 1 minute. For schedules that trigger more than once per minute, the default is `false`.

::: zone-end
::: zone pivot="programming-language-java"

Annotations

The @TimerTrigger annotation on the function defines the schedule using the same string format as CRON expressions. The annotation supports the following settings:

dataType
name
schedule

::: zone-end
::: zone pivot="programming-language-javascript,programming-language-powershell,programming-language-python"

Configuration

The following table explains the binding configuration properties that you set in the function.json file.

function.json property	Description
type	Must be set to "timerTrigger". This property is set automatically when you create the trigger in the Azure portal.
direction	Must be set to "in". This property is set automatically when you create the trigger in the Azure portal.
name	The name of the variable that represents the timer object in function code.
schedule	A CRON expression or a TimeSpan value. A `TimeSpan` can be used only for a function app that runs on an App Service Plan. You can put the schedule expression in an app setting and set this property to the app setting name wrapped in % signs, as in this example: "%ScheduleAppSetting%".
runOnStartup	If `true`, the function is invoked when the runtime starts. For example, the runtime starts when the function app wakes up after going idle due to inactivity. when the function app restarts due to function changes, and when the function app scales out. Use with caution. runOnStartup should rarely if ever be set to `true`, especially in production.
useMonitor	Set to `true` or `false` to indicate whether the schedule should be monitored. Schedule monitoring persists schedule occurrences to aid in ensuring the schedule is maintained correctly even when function app instances restart. If not set explicitly, the default is `true` for schedules that have a recurrence interval greater than or equal to 1 minute. For schedules that trigger more than once per minute, the default is `false`.

::: zone-end

[!INCLUDE app settings to local.settings.json]

Caution

Don't set runOnStartup to true in production. Using this setting makes code execute at highly unpredictable times. In certain production settings, these extra executions can result in significantly higher costs for apps hosted in a Consumption plan. For example, with runOnStartup enabled the trigger is invoked whenever your function app is scaled. Make sure you fully understand the production behavior of your functions before enabling runOnStartup in production.

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
}

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:

Type	Example	When triggered
A specific value	`0 5 * * * *`	Once every hour of the day at minute 5 of each hour
All values (`*`)	`0 * 5 * * *`	At every minute in the hour, beginning at hour 5
A range (`-` operator)	`5-7 * * * * *`	Three times a minute - at seconds 5 through 7 during every minute of every hour of each day
A set of values (`,` operator)	`5,8,10 * * * * *`	Three times a minute - at seconds 5, 8, and 10 during every minute of every hour of each day
An interval value (`/` operator)	`0 /5 * * *`	12 times an hour - at second 0 of every 5th minute of every hour of each day

[!INCLUDE functions-cron-expressions-months-days]

NCRONTAB examples

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

Example	When triggered
`0 /5 * * *`	once every five minutes
`0 0 * * * *`	once at the top of every hour
`0 0 /2 * *`	once every two hours
`0 0 9-17 * * *`	once every hour from 9 AM to 5 PM
`0 30 9 * * *`	at 9:30 AM every day
`0 30 9 * * 1-5`	at 9:30 AM every weekday
`0 30 9 * Jan Mon`	at 9:30 AM every Monday in January

Note

NCRONTAB expression supports both five field and six field format. The sixth field position is a value for seconds which is placed at the beginning of the expression.

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.

[!INCLUDE functions-timezone]

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:

Example	When triggered
"01:00:00"	every hour
"00:01:00"	every minute
"25:00:00:00"	every 25 days
"1.00:00:00"	every day

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 is 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.

Functions version	Setting
2.x (and higher)	`AzureFunctionsWebHost__hostid` environment variable
1.x	`id` in host.json

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

[!div class="nextstepaction"] Go to a quickstart that uses a timer trigger

[!div class="nextstepaction"] Learn more about Azure functions triggers and bindings

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functions-bindings-timer.md

functions-bindings-timer.md

Timer trigger for Azure Functions

Example

In-process

Isolated process

C# Script

Attributes

In-process

Isolated process

C# script

Annotations

Configuration

Usage

NCRONTAB expressions

NCRONTAB examples

NCRONTAB time zones

TimeSpan

Scale-out

Function apps sharing Storage

Retry behavior

Manually invoke a timer trigger

Troubleshooting

Next steps

Files

functions-bindings-timer.md

Latest commit

History

functions-bindings-timer.md

File metadata and controls

Timer trigger for Azure Functions

Example

In-process

Isolated process

C# Script

Attributes

In-process

Isolated process

C# script

Annotations

Configuration

Usage

NCRONTAB expressions

NCRONTAB examples

NCRONTAB time zones

TimeSpan

Scale-out

Function apps sharing Storage

Retry behavior

Manually invoke a timer trigger

Troubleshooting

Next steps