General questions on configuring logs

[auslavs]

Is your question related to a specific version? If so, please specify:

Function Runtime 4, .NET 8 Isolated

What language does your question apply to? (e.g. C#, JavaScript, Java, All)

F#

Question

I'm finding the process of configuring logs increasing frustrating and confusing. I've spent a week trying to reduce our logs to a sensible amount to reduce the thousands of dollars will are billed month for Application Insights.
To me, the logs and docs are not totally clear on which logs should be configured in code, or via the host.json, and furthermore we are seeing different results from deploying the same app with the same settings to different environments.

We currently have the logging section

    "logLevel": {
      "default": "Information",
      "Microsoft": "Warning",
      "Function.HealthCheck-GET": "Warning"
    }

In code, we have removed the Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider rule and added the following filters:

options.AddFilter("Microsoft.AspNetCore", LogLevel.Warning) |> ignore
options.AddFilter("System.Net.Http.HttpClient", LogLevel.Warning) |> ignore

In one environment we have successfully removed all the health check logs, however they still persist in another.
I have manually downloaded the deployed zip (we run from package) and confirmed that the same host.json file is in both.

I have also tried adding "Host.Results": "Warning", to the host.json however this removes all "Requests" from the app insights logs.

In summary my questions are:

1. What is the correct way to remove all information messages for a HTTP trigger, including messages from the app and the host?
2. Is setting Host.Results to Warning expected to remove all Requests logs from App Insights?
3. Is there anything I could check other than host.json and filters I have set up in Program.fs that could affect logging? (Note: I have turned off sampling for both environments).
4. Can we please have some clearer documentation on logging, especially when it comes to Isolated Workers.

Thanks

[auslavs]

I have checked that both environments are using Runtime Version 4.1041.200.25360.
But the one without the HealthCheck logs is running on a consumption plan, but the one with the extra logs that should be omitted is on a premium plan.

[jviau]

@auslavs if you are using dotnet isolated (aka "out of proc"), then there are two processes you need to configure log filters for independently. (1) The host via host.json and (2) the worker (your app) via whatever method you want (in code, a config json file you load -- but don't load host.json in your process).

[lasyan3]

@jviau you answer is, from my point of view, irrelevant as you only give generic answer to the very specific questions of @auslavs . We expect better answers than just the one we can found by ourself in the [really messy] documentation.

[auslavs]

Thanks @lasyan3 for your support and I agree that the answer was not that helpful.
However I did raise another issue around the same time that did get another answer that might provide some insight.

11243

From what I can gather there looks to be little to no effort put into the current logging arrangement because the focus seems to be on the new Open Telemetry packages.

Hopefully we see some improvement when they come into GA, because things have been a bit of a mess ever since isolated workers came in.

[lasyan3]

@auslavs I finally found a configuration which removes all logs but the one we want!

• The function must be using isolated model (.NET 8 currently but may be compatible with others versions).
• The only packages referenced for logging are (be sure to update to latest version!):

  Microsoft.ApplicationInsights.WorkerService (2.23.0)
  Microsoft.Azure.Functions.Worker.ApplicationInsights (2.50.0)

• Program.cs looks like (IHostApplicationBuilder model as described .NET Generic Host:

using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Builder;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var builder = FunctionsApplication.CreateBuilder(args);

builder.ConfigureFunctionsWebApplication();

builder.Services
    .AddApplicationInsightsTelemetryWorkerService(options =>
    {
        // Disable DEPENDENCY logs
        options.EnableDependencyTrackingTelemetryModule = false;
        //options.EnableHeartbeat = false;
        //options.EnableDiagnosticsTelemetryModule = false;
        //options.EnablePerformanceCounterCollectionModule = false;
        //options.EnableEventCounterCollectionModule = false;
        //options.EnableAppServicesHeartbeatTelemetryModule = false;
        //options.EnableAzureInstanceMetadataTelemetryModule = false;
    })
    .ConfigureFunctionsApplicationInsights();

builder.Logging.Services.Configure<LoggerFilterOptions>(options =>
{
    // The Application Insights SDK adds a default logging filter that instructs ILogger to capture only Warning and more severe logs. Application Insights requires an explicit override.
    // Log levels can also be configured using appsettings.json. For more information, see https://learn.microsoft.com/azure/azure-monitor/app/worker-service#ilogger-logs
    LoggerFilterRule defaultRule = options.Rules.FirstOrDefault(rule => rule.ProviderName
        == "Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider");
    if (defaultRule is not null)
    {
        options.Rules.Remove(defaultRule);
    }
});

builder.Build().Run();

• host.json (logging section only):

"logLevel": {
    "default": "Error",
    "Function": "Error"
}

• appsettings.json (replaces logging section from local.settings.json):

{
  "Logging": {
    "LogLevel": {
      "Default": "Error",
      "Host": "Error",
      "Function": "Error",
      "Microsoft": "Error",
      "<FunctionNamespace>": "Information"
    }
  }
}

After you added appsettings.json into your project, be sure to check the behavior for running CopyToOutputDirectory and for publishing CopyToPublishDirectory or else it will never be detected by the application.
The key is to use appsettings.json instead of local.settings.json for logging configuration, try for your own and you'll see the behavior is different (don't know exactly why).
Hope this will help!
I didn't try the new OpenTelemetry SDK as it's still in preview right now.
Thanks for @jviau for his help and sorry for my previous comment I overreacted a bit.
For reference: NET 8 - Isolated - Logging issues when namespace change

[lasyan3]

Side note: be sure to update the NuGet packages to have the latest versions of the Microsoft.Azure.Functions.Worker.* (especially v2!) or you'll experience like me logs filter rules not working 😅