LogOtter.SimpleHealthChecks

SimpleHealthChecks

A library to expose health checks over HTTP for use in worker services without using the Microsoft.NET.Sdk.Web SDK.

Usage

1. Register Microsoft.Extensions.Diagnostics.HealthChecks as normal

services
    .AddHealthChecks()
    .AddCheck<MyCustomCheck>("CustomCheck")

2. Register the SimpleHealthChecks and expose an endpoint

services
    .AddSimpleHealthChecks()
    .AddEndpoint("/health")

Options

By default, the health checks we be exposed on port 80 on all IP addresses. To configure, set the SimpleHealthCheckHostOptions

services
    .AddSimpleHealthChecks(options => {
        options.Host = "127.0.0.1";
        options.Port = 8080;
    });

Customize

Healthcheck endpoints can be filter checks and customize their response in the same way as the Microsoft.Extensions.Diagnostics.HealthChecks can.

Example: Filter checks for different endpoints

services
    .AddSimpleHealthChecks()
    .AddEndpoint("/health/ready", new SimpleHealthCheckOptions()
    {
        Predicate = check => check.Tags.Contains("ready"),
    })
    .AddEndpoints("/health/live", new SimpleHealthCheckOptions());

Example: Custom response

services
    .AddSimpleHealthChecks()
    .AddEndpoint("/health", new SimpleHealthCheckOptions
    {
        ResponseWriter = WriteResponse
    });

private static Task WriteResponse(HttpListenerContext context, HealthReport healthReport)
{
    context.Response.Headers[HttpRequestHeader.ContentType] = "application/json; charset=utf-8";

    var options = new JsonWriterOptions { Indented = true };

    using var memoryStream = new MemoryStream();
    using (var jsonWriter = new Utf8JsonWriter(memoryStream, options))
    {
        jsonWriter.WriteStartObject();
        jsonWriter.WriteString("status", healthReport.Status.ToString());
        jsonWriter.WriteStartObject("results");

        foreach (var healthReportEntry in healthReport.Entries)
        {
            jsonWriter.WriteStartObject(healthReportEntry.Key);
            jsonWriter.WriteString("status", healthReportEntry.Value.Status.ToString());
            jsonWriter.WriteString("description", healthReportEntry.Value.Description);
            jsonWriter.WriteStartObject("data");

            foreach (var item in healthReportEntry.Value.Data)
            {
                jsonWriter.WritePropertyName(item.Key);

                JsonSerializer.Serialize(jsonWriter, item.Value, item.Value?.GetType() ?? typeof(object));
            }

            jsonWriter.WriteEndObject();
            jsonWriter.WriteEndObject();
        }

        jsonWriter.WriteEndObject();
        jsonWriter.WriteEndObject();
    }

    return context.Response.OutputStream.WriteAsync(memoryStream.ToArray().AsMemory()).AsTask();
}

Running locally

In order to run locally, you'll either need to run with Admin permissions or run netsh as an administrator first:

# Run as Administrator
# Note: change port 80 if required
netsh http add urlacl url=http://+:80/ user=$env:USERDOMAIN\$env:USERNAME