CustomHealthCheck.md

sidebar_position	11
sidebar_label	Create custom health checks

How to create custom health checks

To create a custom health check, either implement the IHealthCheck interface or inherit from the SingleResultHealthCheck abstract class.

For custom health checks that generate a single result, inherit from SingleResultHealthCheck, override the CheckAsync method, and optionally specify parameters for the base constructor.

public class MyHealthCheck : SingleResultHealthCheck
{
    public MyHealthCheck()
      : base(componentName: "my", measurementName: "healthCheck",
        componentType: "example", componentId: "2d458535-c9a8-45be-91c2-dfd30b7a093e")
    {
    }

    protected override Task CheckAsync(HealthCheckResult result, CancellationToken cancellationToken)
    {
        // TODO: Perform the actual health check, setting the Status property accordingly.
        result.Status = HealthStatus.Pass;
        return Task.CompletedTask;
    }
}

---

For custom health checks that generate multiple results, implement the IHealthCheck interface directly.

public class AnotherHealthCheck : IHealthCheck
{
    public AnotherHealthCheck(string componentName = "another", string measurementName = "healthCheck",
        string componentType = "example", string componentId = "224ee0cd-e838-4ea9-95af-2bd31dc42850")
    {
        ComponentName = componentName;
        MeasurementName = measurementName;
        ComponentType = componentType;
        ComponentId = componentId;
    }

    public string ComponentName { get; }
    public string MeasurementName { get; }
    public string ComponentType { get; }
    public string ComponentId { get; }

    public async Task<IReadOnlyList<HealthCheckResult>> CheckAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        var results = new List<HealthCheckResult>();

        var result1 = this.CreateHealthCheckResult();
        result1.Status = HealthStatus.Pass;
        results.Add(result1);

        var result2 = this.CreateHealthCheckResult();
        result2.Status = HealthStatus.Warn;
        result2.Output = "This message should describe why the status is Warn.";
        results.Add(result2);

        return results;
    }
}

.NET Framework 3.5 and 4.0

In .NET Framework 4.0 and below, there is no support for async methods, so the IHealthCheck interface and SingleResultHealthCheck abstract class have synchronous methods instead. Here is the signatures of the synchronous methods:

public interface IHealthCheck
{
    IList<HealthCheckResult> Check();
}

public abstract class SingleResultHealthCheck : IHealthCheck
{
    protected abstract void Check(HealthCheckResult result);
}