scheduled fn app intermittent and not showing in innvocations tab

Hi Olly Wenn,

Thank you for reaching out to the Microsoft Q&A community. Based on your description, you are encountering two separate issues: the Function intermittently failing to trigger, and the successful executions not appearing in the Azure Portal.

Here is how you can resolve both issues:

1. Resolving the Empty Invocations Tab (0 runs showing): The Invocations tab in the Azure Portal does not read logs from the Function App directly; it relies entirely on Azure Application Insights. If the tab shows 0 runs despite your function successfully sending emails, your app is either disconnected from Application Insights, or the telemetry is being dropped/sampled out.

• Resolution: Navigate to your Function App in the portal -> Environment variables (or Configuration -> Application settings). Ensure that you have a valid setting for APPLICATIONINSIGHTS_CONNECTION_STRING. If it is missing or pointing to a deleted instance, the Invocations tab will remain blank.

2. Resolving Intermittent Timer Trigger Failures: Intermittent execution drops for scheduled functions are usually tied to the hosting plan's idle state or issues with Azure Storage locks.

• If using a Dedicated (App Service) Plan: Your function app might be going to sleep after periods of inactivity. You must enable the "Always On" setting.
  • Resolution: Go to your Function App -> Configuration -> General settings -> toggle Always On to On.
• If using a Consumption Plan: Timer triggers rely on Azure Storage to maintain a central lock (so that if your app scales out, the timer only fires once). If the storage account configured in AzureWebJobsStorage is inaccessible, restricted by a firewall, or shared improperly with other function apps, it will miss executions.
  • Resolution: Verify that the AzureWebJobsStorage connection string is valid and the storage account is healthy. Also, avoid sharing the exact same storage account across multiple distinct function apps without specifying different Host IDs, as they can conflict over the timer locks.
• Official Documentation: "Timer triggers use a storage lock to ensure that there's only one timer instance running... If the storage account is inaccessible, the timer trigger might not fire." (Source: Timer trigger for Azure Functions - Troubleshooting)

If you reconnect Application Insights and still experience missed runs, you can query the exceptions table in App Insights to see if long-running executions are causing overlapping locks.

Let us know if checking these settings helps resolve the behavior.

Note: This response is drafted with the help of AI systems.