Warning logs are written to eventlog.xml file by default

[soninaren]

For dotnet-isolated app, All the warning log statements are written to C:\home\LogFiles\eventlog.xml. The issue can be reproduced by creating a dotnet-isolated app on windows with consumption plan and adding a warning statement like the one below to an httpTrigger function.

We should not be warning logs to eventlog.xml file by default.

Sample Host.json

{
    "version": "2.0",
    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    }
}

Sample httpTrigger

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace FunctionApp1
{
    public class HttpTrigger1
    {
        private readonly ILogger<HttpTrigger1> _logger;

        public HttpTrigger1(ILogger<HttpTrigger1> logger)
        {
            _logger = logger;
        }

        [Function("HttpTrigger1")]
        public IActionResult Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req)
        {
            _logger.LogInformation("C# HTTP trigger function processed a request.");
            _logger.LogWarning("Warning: C# HTTP trigger function processed a request.");
            return new OkObjectResult("Welcome to Azure Functions!");
        }
    }
}

EventLog.xml

<Event>
        <System>
            <Provider Name=".NET Runtime"/>
            <EventID>1000</EventID>
            <Level>2</Level>
            <Task>0</Task>
            <Keywords>Keywords</Keywords>
            <TimeCreated SystemTime="2025-01-06T23:29:45Z"/>
            <EventRecordID>215192484</EventRecordID>
            <Channel>Application</Channel>
            <Computer>10-30-0-213</Computer>
            <Security/>
        </System>
        <EventData>
            <Data>Category: Company.Function.HttpTrigger1
EventId: 0
SpanId: 7bc6584d3be812b1
TraceId: 320e172a69ac9a7823693d63e127194a
ParentId: 0000000000000000
AzureFunctions_InvocationId: 1b651c08-5a7d-4eab-bb27-268e60698613
AzureFunctions_FunctionName: HttpTrigger1

Warning: C# HTTP trigger function processed a request.
</Data>
        </EventData>
    </Event>
</Events>