Issue with NCRONTAB Expression in Azure WebJobs.

Question

Dear Team,

I am currently facing an issue while configuring a scheduled WebJob in Azure App Service.

I am attempting to schedule the WebJob to run every Saturday at 5:00 AM using the NCRONTAB expression:

0 0 5 * * 6

However, I consistently receive the error message: "Please provide a valid cron expression."

Could you please confirm if there have been any recent changes to the NCRONTAB format or advise on the correct expression to achieve this schedule?

Your guidance on this matter would be greatly appreciated.

Thank you for your support.

Best regards,
Aashish Goley

Answer 1

Hello @Aashish Goley

Glad that you're able to find the work around using a settings.job file. Re-iterating the workaround.

1. In your WebJob's root folder (inside the ZIP), create a file called settings.job with this content (adjust the cron as needed) Knowledge base

         {
        
      )
   

2. Zip it up and upload via the portal under Triggered > Upload your zip (choose Manual trigger type).
3. Head to Configuration > General settings and turn Always On to Yes (if on Basic tier or higher) to ensure it fires reliably.

Reference :

https://learn.microsoft.com/en-us/azure/app-service/webjobs-create?tabs=windowscode#ncrontab-expressions

https://learn.microsoft.com/en-us/azure/app-service/tutorial-webjobs?tabs=windows&pivots=dotnet

Please comment below in case you have any queries.

Answer 2

Hi,

UPDATE: My original workaround seems not to be working reliably, so Aashish chose to instead include settings.job file at the root of the webjob's .zip file. Excerpt from documentation:

NCRONTAB expressions

An NCRONTAB expression is similar to a CRON expression, but includes an additional sixth field at the beginning for time precision in seconds. You can enter an NCRONTAB expression in the portal or include a settings.job file at the root of your WebJob .zip file, as in the following example:

{
    "schedule": "0 */15 * * * *"
}

Please see Aashish's comment below this answer.

---

Quick way is to use 5 digit CRON to get around portal not accepting 6 digit NCRONTAB expression, similar to below:

0 5 * * 6

Please note the default is to use UTC time zone, so you may need to adjust the 5 in above expression so that it executes at 5 AM in the desired time zone.

NCRONTAB time zones

https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-timer?tabs=python-v2%2Cisolated-process%2Cnodejs-v4&pivots=programming-language-csharp#ncrontab-time-zones

Please click Accept Answer and upvote if the above was helpful.

Thanks.

-TP

Answer 3

For Azure App Service WebJobs, NCRONTAB supports both five-field and six-field formats, where the optional first field is seconds. The expression being used:

0 0 5 * * 6

is a six-field expression and is syntactically valid NCRONTAB for “at 05:00:00 every Saturday”:

• Seconds: 0
• Minutes: 0
• Hours: 5
• Day-of-month: *
• Month: *
• Day-of-week: 6 (Saturday)

This is the same six-field style used in the documented examples such as:

• 0 30 9 * * 1-5 → at 9:30 AM every weekday
• 0 30 9 * Jan Mon → at 9:30 AM every Monday in January

There is no change indicated to the NCRONTAB format itself; six-field expressions with seconds in the first position are still supported.

To schedule the WebJob for every Saturday at 5:00 AM, use exactly:

0 0 5 * * 6

If the portal still reports it as invalid, verify that the WebJob UI is expecting NCRONTAB (with seconds) and not a five-field cron variant, and re-enter the expression in that field. The documented pattern for “every minute” in WebJobs is also six-field (0 0/1 * * * *), which confirms that the seconds field is expected there.

---

References:

• Tutorial: Build a scheduled WebJob
• Timer trigger for Azure Functions (programming-language-csharp)
• Timer trigger for Azure Functions (programming-language-javascript)
• Timer trigger for Azure Functions (programming-language-typescript)
• Timer trigger for Azure Functions (programming-language-python)
• Timer trigger for Azure Functions (programming-language-java)
• Timer trigger for Azure Functions (programming-language-powershell)