How do you use health checks in .NET Core?

In .NET Core, you can use health checks to monitor the health of your application's dependencies and components, such as databases, external services, and disk space. Health checks can help you quickly identify issues and troubleshoot problems before they cause downtime.

To use health checks in .NET Core, you can add the Microsoft.Extensions.Diagnostics.HealthChecks NuGet package to your project. Then, you can define your health checks by creating classes that implement the IHealthCheck interface. The IHealthCheck interface has a single CheckHealthAsync method that returns a Task<HealthCheckResult>.

Here's an example of a custom health check that checks the status of a database:

public class DatabaseHealthCheck : IHealthCheck
{
    private readonly IDbConnection _dbConnection;

    public DatabaseHealthCheck(IDbConnection dbConnection)
    {
        _dbConnection = dbConnection;
    }

    public async Task<HealthCheckResult> CheckHealthAsync(
        HealthCheckContext context,
        CancellationToken cancellationToken = default(CancellationToken))
    {
        try
        {
            await _dbConnection.OpenAsync(cancellationToken);
        }
        catch (Exception ex)
        {
            return HealthCheckResult.Unhealthy("Database connection failed", ex);
        }

        return HealthCheckResult.Healthy();
    }
}


Once you have defined your health checks, you can register them with the IHealthChecksBuilder in the ConfigureServices method of your Startup class:

public void ConfigureServices(IServiceCollection services)
{
    services.AddHealthChecks()
        .AddCheck<DatabaseHealthCheck>("database");
}


This registers the DatabaseHealthCheck as a health check named "database". You can then use the UseHealthChecks method in your app.UseEndpoints configuration to map the health check endpoint to a specific URL:

app.UseEndpoints(endpoints =>
{
    endpoints.MapHealthChecks("/health");
});


This maps the health check endpoint to /health. You can then make requests to /health to get a JSON response that indicates the status of your application's health checks.