7. ASP .Net core - Fundamentals - Logs

 This series is a collection of knowledge about ASP .NET Core. It just is my notes.

Part 1: Startup file.

Part 2: DI.

Part 3: Middleware.

Part 4: Host and Servers.

Part 5: Configurations.

Part 6: Environment.

Part 8: Error Handling.

Part 9: Routing.

Part 10: Make an HTTP Request.

Part 11: Static files.

Part 12: Authentication and Authorization.

Part 13: CORS.

The log is one of the approaches to troubleshoot the application. So, Don't forget to implement the logs for your application.

Which kind of log provider is best: built-in or third party???

If your app integrates with Azure or deploys on Azure => use Application Insight

If your app deploys on-premise => use a structured log third party, for example, NLog

1. Log level

LogLevel	Value	Method	Description
Trace	0	LogTrace	Contain the most detailed messages. These messages may contain sensitive app data. These messages are disabled by default and should not be enabled in production.
Debug	1	LogDebug	For debugging and development. Use caution in production due to the high volume.
Information	2	LogInformation	Tracks the general flow of the app. May have long-term value.
Warning	3	LogWarning	For abnormal or unexpected events. Typically includes errors or conditions that don't cause the app to fail.
Error	4	LogError	For errors and exceptions that cannot be handled. These messages indicate a failure in the current operation or request, not an app-wide failure.
Critical	5	LogCritical	For failures that require immediate attention. Examples: data loss scenarios, out of disk space.
None	6		Specifies that a logging category should not write any messages.

2. Built-in logging provider
• Refer Azure Application Insight
  

3. Third-party logging provider
• NLog
• Serilog

4. How to use AppInsight and Telemetry

a. step 1: Enable .net core API use AppInsight

• Create an AppInsight resource via Azure Portal.
• Get the information of instrumentation key or connection string

b. step 2: Configure something of AppInsight in .net core API

• Add Nuget package
• Microsoft.ApplicationInsights.AspNetCore
• ConfigureService

public void ConfigureServices(IServiceCollection services)

{

...

services.AddApplicationInsightsTelemetry(Configuration["ApplicationInsights:ConnectionString"]);

}

• Important: some Azure region requires a connection string instead of  Instrumentation key
• Note: You can also configure AppInsight following these recommendations

It's best practice to have an extension method to do the configuration, see:

public static IServiceCollection AddTelemetry(this IServiceCollection services, IConfiguration configuration)

{

services.AddApplicationInsightsTelemetry(options =>

{

var appSettings =configuration.GetAppSettings();

options.InstrumentationKey = appSettings.AIKey;

//we want to know when the worker stops

options.EnableHeartbeat = true;

options.EnableAdaptiveSampling = false;

});

services.AddTelemetryService(configuration.GetAppSettings());

return services;

}

c. step 3 raise custom metric in AppInsight

• Use TelemetryClient

TelemetryClient _telemetryClient;

...

[HttpGet]

public string Get()

{

_telemetryClient.TrackMetric("CustomMetricExample22", 1, new Dictionary<string, string> { { "Value", "22" } });

...

}

• The best practice is to create a wrapper class for TelemetryClient

References:

[Microsoft Learn] - Logging