Function has no invocation records or 'live' logs

ZZ 80

My function app is configured as such but I don't get invocation records, or logs in the live streaming window. Logs can be found in application insights through 'table > traces'. What is wrong with my function or configuration?

When I click to see invocations, I see an empty list after 10:19 today, but that is wrong because I made lots of calls later, you can see this in the applications insights.

Screenshot from 2025-01-27 15-50-51

When I choose the Logs window like below, and then make a call to the function, I also do not get anything appearing in the window.

Screenshot from 2025-01-27 15-52-06

But as you can see, application insights can show all the logs if I click 'Table > Traces'

Screenshot from 2025-01-27 15-51-37

Function app json:

{
  "version": "2.0",
  "functionTimeout": "00:10:00",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "excludedTypes": ""
      }
    },
    "logLevel": {
      "default": "Warning",
      "Function": "Information",
      "Host.Aggregator": "Trace",
      "Host.Results": "Error"
    },
    "extensions": {
      "queues": {
        "maxDequeueCount": 1
      }
    }
  },
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[4.*, 5.0.0)"
  }
}

Khadeer Ali 3,675 Reputation points Microsoft Vendor

2025-01-27T16:53:36.21+00:00
@ZZ ,

Welcome to Microsoft Q&A Platform!
Thanks for reaching out. It sounds like your Function App is sending logs to Application Insights (you can see them in the 'traces' table), but the invocation records and live logs aren't showing up. Let's troubleshoot this. Here are a few key areas to investigate:

Sampling: Application Insights uses sampling to reduce the volume of telemetry data. If the sampling settings are too restrictive, it can prevent some logs from being recorded. Check the maxTelemetryItemsPerSecond setting and consider temporarily disabling sampling to see if that resolves the issue.

Log Levels: The log level configuration determines which messages are recorded. With a default log level of 'Warning,' only warnings and errors are captured. To see more detailed information, including invocation details, adjust the log level to 'Information' or lower in your Function App's configuration settings.

Function App Version: Ensure your Function App is running on version 4 or later. This version has improved integration with Application Insights for log flow. You can verify the runtime version in the Azure portal.

Network Configuration: If your Function App is integrated with a virtual network, ensure that outbound traffic on port 443 is allowed for the Application Insights SDK to send data. Check your network security group rules if applicable.

Diagnostics: The Azure portal provides a built-in diagnostics tool ("Diagnose and solve problems") for Function Apps. This can often identify common configuration issues.

Instrumentation Key: Verify that the correct Application Insights instrumentation key is configured in your Function App's application settings. This key is essential for routing telemetry to the correct Application Insights resource. This is often the most common cause of missing data.

If you've checked all of that and it's still not working, further troubleshooting will be required. Hopefully, one of these steps will resolve the issue!

References:

Application Insights logs are missing or incorrect for Azure Functions apps

Analyze Azure Functions telemetry in Application Insights
ZZ 80 Reputation points

2025-01-27T18:09:27.2233333+00:00
Thanks for your reply.

Sampling - please can you tell me where to look for that parameter to set?

Log levels- I am confused. The default level is 'warning', but my function level is 'information' (Function": "Information") the fact that I can query for logs in application insights suggest the logs are properly captured. They don't appear in the log window and the invocations are not captured is a different matter, isn't it?

Function app version - again please can you tell me where to look for this? I am on Consumption Flex plan, and when I go to 'configuration', I can only see these information:

Network configuration: screenshot as below, not sure what I should look for...
Khadeer Ali 3,675 Reputation points Microsoft Vendor

2025-01-28T12:16:47.5166667+00:00
@ZZ ,

Thank you for providing the additional information.

To address your questions:

Sampling: The sampling settings in your host.json file are currently enabled, meaning not all telemetry data is sent to Application Insights. You can adjust these settings by modifying the maxTelemetryItemsPerSecond or disabling sampling by setting "isEnabled": false. This will help ensure more logs are captured and sent. Please refer to the documentation: Logs are missing or partial

Log Levels: Your log level configuration indicates that the default log level is Warning, but your function's log level is set to Information. This means logs at the Information level and above should be captured. If you can query logs in Application Insights, it suggests that logs are being captured, but they may not appear in the live streaming window due to other configuration issues.

Function App Version: The Consumption Flex plan generally runs on the latest stable version of the Azure Functions runtime. Therefore, you are likely on a recent version, which is beneficial for Application Insights compatibility.

Networking: If a function app is integrated with a virtual network, port 443 must be open for outgoing traffic in your server firewall to allow the Application Insights SDK. However, since there is no vNET integrated with the function app, this can be ignored. Please ensure the Instrumentation Key in your Function App's "Configuration" settings exactly matches the one in your Application Insights resource. Even a simple typo can cause issues!

Let me know what you find after checking these. If it's still not working, we'll need to investigate further
ZZ 80 Reputation points

2025-01-29T14:24:36.23+00:00
Thank you for your help. I have tried a number of things but they still don't work - the live 'logs' dashboard shows nothing even logs are captured by application insights - it is completely blank. And no records of invocations at all.

I changed "isEnabled" to false

I checked my Function App's Configuration but there is no 'Instrumentation Key', see a screenshot below.

I checked 'monitoring > application insights' of my function app and it is showing this - I guess it means my app is connected to the application insights properly:

I also checked 'Monitoring > Logs > Tables > traces' and can see that my logging levels are properly set and logs are there, notice in 'customDimensions' the fields 'loglevel', 'invocationid' are all there, but they just don't show up in the invocations lists, or the live log dashboard. Very frustrating....
Ryan Hill 29,681 Reputation points Microsoft Employee

2025-01-31T00:43:26.6866667+00:00

Hey @ZZ it could be configuration but I can't be sure. Let's take a step back; can you add a new a HTTP trigger to your function and see the invocations of that function?
ZZ 80 Reputation points

2025-01-31T13:58:03.52+00:00
Hi

So I have created a minimal function within my function app environment to test:

import logging import azure.functions as func def main(request: func.HttpRequest) -> func.HttpResponse: if request.method == 'GET': msg='received a GET request' logging.info(msg) return func.HttpResponse(msg, status_code=200) else: return func.HttpResponse("Method not allowed", status_code=405)

Logs are showing if I go 'function name > Logs' and then invoke the function by making a HTTP call. The logs are then printed in the Logs dashboard.

Logs do not show if I invoke the function first, then go to 'function name > Logs'

The list of invocations is still empty. This is like refreshing 20 minutes I made the calls

But again, if you check application insights, all logs are there:
Ryan Hill 29,681 Reputation points Microsoft Employee

2025-02-04T22:07:18.47+00:00

Hi @ZZ, apologies for the late reply. Double check your sample settings or disable it and see if you're start seeing the invocations.
ZZ 80 Reputation points

2025-02-05T19:38:15.96+00:00
Hi, as I said before, I disabled sampling. I don't know if I should open up a support ticket for someone to look at this for us, we are not getting anywhere...

"applicationInsights": { "samplingSettings": { "isEnabled": false, "excludedTypes": "" } },
Ryan Hill 29,681 Reputation points Microsoft Employee

2025-02-05T20:14:05.1733333+00:00

Thanks for responding @ZZ. Let's take the discussion offline via private message so we can gather additional information from you.

Accepted answer

Ryan Hill 29,681 Reputation points Microsoft Employee

2025-02-28T02:12:38.2366667+00:00

Hi @ZZ

Thanks for working offline with me investigating this issue. To benefit the broader community, your missing invocation log entries came down to the logging configuration in your host.json. The Invocation tab pulls records that are saved to the requests table from Host.Results; as documented on https://learn.microsoft.com/en-us/azure/azure-functions/configure-monitoring?tabs=v2#configure-categories. By default, only Warnings are logged for this for Hosts.Results, meaning anything that fails within the host operation, e.g. an unhandled exception or anything that's logged as a warning message.

In order to see everything, you just have to change the logLevel to a lower level, i.e. Information.
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