Function app missing Invocation logs

Question

Function app missing Invocation logs

Pranab Nath 0

Dear Azure Support Team,

I am reaching out to report an issue with invocation logs not appearing in the Azure portal for our Function Apps, specifically for blob event triggers. Despite waiting over 48 hours, the logs have not been populated. This issue is consistent across multiple Function Apps, all running version 4.

We would appreciate your assistance in determining whether this is a platform-related issue or if there might be a misconfiguration on our side. Any guidance or troubleshooting steps to resolve this matter promptly would be greatly appreciated.

Looking forward to your earliest support on this.

Best Regards

FPS

Anonymous

2025-06-12T14:13:35.5+00:00
@Pranab Nath ,
Thanks for reaching out.

To troubleshoot the issue of missing invocation logs for Azure Function Apps with blob event triggers, here are some steps you can follow:

Check Function App Configuration Go to your Function App in the Azure portal, click on "Diagnose and solve problems", and run "Function Configuration Checks". This tool helps identify any misconfigurations that could impact logging.

Confirm Application Insights is Connected Make sure Application Insights is correctly linked to your Function App. Either the APPINSIGHTS_INSTRUMENTATIONKEY or the APPLICATIONINSIGHTS_CONNECTION_STRING should be set properly in the app settings. Missing or incorrect settings can result in no logs being captured.

Check for Sampling in Application Insights Application Insights uses sampling to reduce the amount of telemetry data. If enabled, it might cause some logs to be skipped. You can run a query in Application Insights to see the sampling percentage and adjust as needed.

Review Log Levels in host.json The logging level defined in your host.json file determines how much detail is captured in the logs. Make sure the settings are not too restrictive. For example:

{ "logging": { "logLevel": { "Function": "Information", "default": "Information" } } }

Verify Network Access If your Function App is running inside a virtual network, make sure it allows outbound traffic on port 443, which is required for the telemetry to be sent to Application Insights.

Ensure the Runtime Version is Up to Date Make sure your Function App is using at least version 4.15.2, as later versions include improvements in how logs and telemetry are handled.

If all the above checks are in place and you're still not seeing invocation logs, consider the following:

What permissions does your managed identity have on the storage account?

Has the Function App configuration been validated specifically for blob triggers and managed identity?

Are there warnings or errors in the diagnostic logs or Application Insights that could provide further insights?

Ref Document: Application Insights logs are missing or incorrect for Azure Functions apps
Anonymous

2025-06-13T12:46:42.83+00:00

@Pranab Nath ,

Just checking to see if you got a chance to try the suggested troubleshooting steps.
Pranab Nath 0 Reputation points

2025-06-13T13:39:17.21+00:00
The application insight settings are automatically set in the appsettings during deployment and is not modified. The invocation logs were seen till 4th June.

Log settings in host.json is as below:

"logging": {

"applicationInsights": { "samplingSettings": { "isEnabled": true, "excludedTypes": "Request" } }
Anonymous

2025-06-13T15:00:53.0366667+00:00

@Pranab Nath ,

Please respond over private message to investigate the issue.
RChotu 3,210 Reputation points Microsoft External Staff Moderator

2025-06-19T04:12:37.73+00:00

Just checking to see if you got a chance to try the suggested above host.json

1 answer

Your answer

Anonymous

2025-06-13T12:46:42.83+00:00

@Pranab Nath ,

Just checking to see if you got a chance to try the suggested troubleshooting steps.
Pranab Nath 0 Reputation points

2025-06-13T13:39:17.21+00:00

The application insight settings are automatically set in the appsettings during deployment and is not modified. The invocation logs were seen till 4th June.

Log settings in host.json is as below:

"logging": {

"applicationInsights": { "samplingSettings": { "isEnabled": true, "excludedTypes": "Request" } }
Anonymous

2025-06-13T15:00:53.0366667+00:00

@Pranab Nath ,

Please respond over private message to investigate the issue.
RChotu 3,210 Reputation points Microsoft External Staff Moderator

2025-06-19T04:12:37.73+00:00

Just checking to see if you got a chance to try the suggested above host.json

Answer 1

RChotu 3,210 Microsoft External Staff Moderator

Try to check it with using below host.json:


{

    "version": "2.0",

  "logging": {

    "applicationInsights": {

      "samplingSettings": {

        "isEnabled": true,

        "excludedTypes": "Request"

      },

      "enableLiveMetricsFilters": true

    },

    "default": "Information",

    "Function.Function1": "Information"

  }

}

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Function app missing Invocation logs

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