Why is ILogger not logging to Azure app insights?

Question

I am testing out the code directly out of here for a console app: https://learn.microsoft.com/en-us/azure/azure-monitor/app/ilogger#

I basically copied the code and pointed it to a new azure app insights instance. However, none of the logs are showing up in app insights. Am I missing anything?

 static void Main(string[] args)
        {
            // Create DI container.
            IServiceCollection services = new ServiceCollection();

            // Add the logging pipelines to use. We are using Application Insights only here.
            services.AddLogging(loggingBuilder =>
            {
                // Optional: Apply filters to configure LogLevel Trace or above is sent to ApplicationInsights for all
                // categories.
                loggingBuilder.AddFilter<ApplicationInsightsLoggerProvider>("", LogLevel.Trace);
                loggingBuilder.AddApplicationInsights(******);
            });

            // Build ServiceProvider.
            IServiceProvider serviceProvider = services.BuildServiceProvider();

            ILogger<Program> logger = serviceProvider.GetRequiredService<ILogger<Program>>();


            logger.LogCritical("critical message working");
            // Begin a new scope. This is optional. Epecially in case of AspNetCore request info is already
            // present in scope.
            using (logger.BeginScope(new Dictionary<string, object> { { "Method", nameof(Main) } }))
            {
                logger.LogWarning("Logger is working - warning"); // this will be captured by Application Insights.

            }
        }

Answer 1

The code is correct, but you are hitting a known issue with ApplicationInsights and Console apps - the app is dying before ApplicationInsights can send the data to the backend. (data is not sent immediately, but batched and sent at intervals.)

Adding a sleep of ~30 secs should help your case. Thread.Sleep(31000);

In regular console apps, docs suggest doing an explicit flush. https://learn.microsoft.com/en-us/azure/azure-monitor/app/console#full-example

But in the ILogger case, you don't control the TelemetryClient instance. So your best alternative is to control the channel, and call flush on the channel followed by a small sleep. Modified code is given below.

class Program
    {
        static void Main(string[] args)
        {
            // Create DI container.
            IServiceCollection services = new ServiceCollection();

            var channel = new InMemoryChannel();

            services.Configure<TelemetryConfiguration>(
              (config) =>
                {
                    config.TelemetryChannel = channel;                    
                }
           );

            // Add the logging pipelines to use. We are using Application Insights only here.
            services.AddLogging(loggingBuilder =>
            {
                // Optional: Apply filters to configure LogLevel Trace or above is sent to ApplicationInsights for all
                // categories.
                loggingBuilder.AddFilter<ApplicationInsightsLoggerProvider>("", LogLevel.Trace);
                loggingBuilder.AddApplicationInsights("***");
            });

            // Build ServiceProvider.
            IServiceProvider serviceProvider = services.BuildServiceProvider();

            ILogger<Program> logger = serviceProvider.GetRequiredService<ILogger<Program>>();


            logger.LogCritical("critical message working");
            // Begin a new scope. This is optional. Epecially in case of AspNetCore request info is already
            // present in scope.
            using (logger.BeginScope(new Dictionary<string, object> { { "Method", nameof(Main) } }))
            {
                logger.LogWarning("Logger is working - warning"); // this will be captured by Application Insights.

            }

            channel.Flush();
            Thread.Sleep(1000);            
        }
    }