Configurable schedule of timer triggered Azure functions

As you probably know it is possible to create Azure functions which will be triggered automatically by schedule specified by CRON expression. In order to do that create timer-triggered Azure function and specify CRON expression like this:

public static class MyFunc
{
 [FunctionName("MyFunc")]
 public static void Run([TimerTrigger("0 */15 * * * *")] TimerInfo myTimer, TraceWriter log)
 {
  ...
 }
} 

Here we defined function which will run every 15 minutes. But with this approach if you will want to change schedule on production env you will need to recompile the package and re-upload it to Azure. It is more convenient to create schedule configurable. In order to do that use the following syntax:

public static class MyFunc
{
 [FunctionName("MyFunc")]
 public static void Run([TimerTrigger("%MyFuncSchedule%")] TimerInfo myTimer, TraceWriter log)
 {
  ...
 }
}

At the same time in AF app settings you need to have MyFuncSchedule app setting:

{
  "IsEncrypted": false,
  "Values": {
    "MyFuncSchedule": "0 */15 * * * *",
  },
  "Host": {
    "CORS": "*"
  }
}

In this case it will be possible to change timer schedule for your timer-triggered Azure function without re-compiling and re-uploading the package.

Note 1. App setting with schedule should be added before to upload package with compiled Azure functions. Otherwise function won’t run.

Note 2. When you change Azure function app settings – currently running instances will be terminated. After that new instances will use updated app settings.