[HealthChecks] Register health check services & checks

src/WebJobs.Script.WebHost/WebHostServiceCollectionExtensions.cs

@@ -13,6 +13,7 @@
 using Microsoft.Azure.WebJobs.Script.Config;
 using Microsoft.Azure.WebJobs.Script.Configuration;
 using Microsoft.Azure.WebJobs.Script.Diagnostics;
+using Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks;
 using Microsoft.Azure.WebJobs.Script.Grpc;
 using Microsoft.Azure.WebJobs.Script.Metrics;
 using Microsoft.Azure.WebJobs.Script.Middleware;
@@ -236,6 +237,9 @@ public static void AddWebJobsScriptHost(this IServiceCollection services, IConfi
 
             // Add AzureBlobStorageProvider to WebHost (also needed for ScriptHost) and AzureTableStorageProvider
             services.AddAzureStorageProviders();
+
+            // Add health checks
+            services.AddHealthChecks().AddWebJobsScriptHealthChecks();
         }
 
         internal static void AddHostingConfigOptions(this IServiceCollection services, IConfiguration configuration)

src/WebJobs.Script/Diagnostics/HealthChecks/HealthCheckExtensions.cs

@@ -0,0 +1,59 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks
+{
+    /// <summary>
+    /// Health check related extension methods.
+    /// </summary>
+    internal static class HealthCheckExtensions
+    {
+        /// <summary>
+        /// Registers all health check services required for the functions host. Should be called
+        /// on the WebHost.
+        /// </summary>
+        /// <param name="builder">The builder to register health checks with.</param>
+        /// <returns>The original builder, for call chaining.</returns>
+        public static IHealthChecksBuilder AddWebJobsScriptHealthChecks(this IHealthChecksBuilder builder)
+        {
+            ArgumentNullException.ThrowIfNull(builder);
+            builder
+                .AddWebHostHealthCheck()
+                .AddScriptHostHealthCheck();
+
+            return builder;
+        }
+
+        /// <summary>
+        /// Adds a health check for the web host lifecycle.
+        /// </summary>
+        /// <param name="builder">The builder to register health checks with.</param>
+        /// <returns>The original builder, for call chaining.</returns>
+        public static IHealthChecksBuilder AddWebHostHealthCheck(this IHealthChecksBuilder builder)
+        {
+            ArgumentNullException.ThrowIfNull(builder);
+            builder.AddCheck<WebHostHealthCheck>(
+                HealthCheckNames.WebHostLifeCycle, tags: [HealthCheckTags.Liveness]);
+            return builder;
+        }
+
+        /// <summary>
+        /// Adds a health check for the script host lifecycle.
+        /// </summary>
+        /// <param name="builder">The builder to register health checks with.</param>
+        /// <returns>The original builder, for call chaining.</returns>
+        public static IHealthChecksBuilder AddScriptHostHealthCheck(this IHealthChecksBuilder builder)
+        {
+            ArgumentNullException.ThrowIfNull(builder);
+            builder.AddCheck<ScriptHostHealthCheck>(
+                HealthCheckNames.ScriptHostLifeCycle, tags: [HealthCheckTags.Readiness]);
+            return builder;
+        }
+    }
+}

src/WebJobs.Script/Diagnostics/HealthChecks/HealthCheckNames.cs

@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+namespace Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks
+{
+    /// <summary>
+    /// Contains names used for health checks in the Azure Functions host.
+    /// </summary>
+    internal static class HealthCheckNames
+    {
+        private const string Prefix = "az.functions.";
+
+        /// <summary>
+        /// The 'az.functions.web_host.lifecycle' check monitors the lifecycle of the web host.
+        /// </summary>
+        public const string WebHostLifeCycle = Prefix + "web_host.lifecycle";
+
+        /// <summary>
+        /// The 'az.functions.script_host.lifecycle' check monitors the lifecycle of the script host.
+        /// </summary>
+        public const string ScriptHostLifeCycle = Prefix + "script_host.lifecycle";
+    }
+}

src/WebJobs.Script/Diagnostics/HealthChecks/HealthCheckTags.cs

@@ -0,0 +1,37 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+namespace Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks
+{
+    /// <summary>
+    /// Contains tags used for health checks in the Azure Functions host.
+    /// </summary>
+    internal static class HealthCheckTags
+    {
+        private const string Prefix = "az.functions.";
+
+        /// <summary>
+        /// The 'az.functions.liveness' tag is used for liveness checks in the Azure Functions host.
+        /// </summary>
+        /// <remarks>
+        /// Liveness checks are used to determine if the host is alive and responsive.
+        /// </remarks>
+        public const string Liveness = Prefix + "liveness";
+
+        /// <summary>
+        /// The 'az.functions.readiness' tag is used for readiness checks in the Azure Functions host.
+        /// </summary>
+        /// <remarks>
+        /// Readiness checks are used to determine if the host is ready to process requests.
+        /// </remarks>
+        public const string Readiness = Prefix + "readiness";
+
+        /// <summary>
+        /// The 'az.functions.configuration' tag is used for configuration-related health checks in the Azure Functions host.
+        /// </summary>
+        /// <remarks>
+        /// These are typically customer configuration related, such as configuring AzureWebJobsStorage access.
+        /// </remarks>
+        public const string Configuration = Prefix + "configuration";
+    }
+}

src/WebJobs.Script/Diagnostics/HealthChecks/ScriptHostHealthCheck.cs

@@ -8,6 +8,10 @@
 
 namespace Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks
 {
+    /// <summary>
+    /// A health check that reports the status of the script host lifecycle.
+    /// </summary>
+    /// <param name="manager">The script host manager.</param>
     internal class ScriptHostHealthCheck(IScriptHostManager manager) : IHealthCheck
     {
         private readonly IScriptHostManager _manager = manager ?? throw new ArgumentNullException(nameof(manager));
@@ -33,6 +37,7 @@ internal class ScriptHostHealthCheck(IScriptHostManager manager) : IHealthCheck
         private static readonly Task<HealthCheckResult> _unhealthyUnknown =
             Task.FromResult(HealthCheckResult.Unhealthy("Script host in unknown state"));
 
+        /// <inheritdoc />
         public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
             => _manager.State switch
             {

src/WebJobs.Script/Diagnostics/HealthChecks/WebHostHealthCheck.cs

@@ -8,13 +8,18 @@
 
 namespace Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks
 {
+    /// <summary>
+    /// A health check that reports the status of the web host lifecycle.
+    /// </summary>
+    /// <param name="lifetime">The application lifetime.</param>
     internal class WebHostHealthCheck(IHostApplicationLifetime lifetime) : IHealthCheck
     {
         private static readonly Task<HealthCheckResult> _healthy = Task.FromResult(HealthCheckResult.Healthy());
         private static readonly Task<HealthCheckResult> _unhealthyNotStarted = Task.FromResult(HealthCheckResult.Unhealthy("Not Started"));
         private static readonly Task<HealthCheckResult> _unhealthyStopping = Task.FromResult(HealthCheckResult.Unhealthy("Stopping"));
         private static readonly Task<HealthCheckResult> _unhealthyStopped = Task.FromResult(HealthCheckResult.Unhealthy("Stopped"));
 
+        /// <inheritdoc />
         public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
         {
             bool isStopped = lifetime.ApplicationStopped.IsCancellationRequested;

test/WebJobs.Script.Tests/Diagnostics/HealthChecks/HealthCheckExtensionsTests.cs

@@ -0,0 +1,122 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.Reflection;
+using AwesomeAssertions;
+using Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Moq;
+using Xunit;
+
+namespace Microsoft.Azure.WebJobs.Script.Tests.Diagnostics.HealthChecks
+{
+    public class HealthCheckExtensionsTests
+    {
+        [Fact]
+        public void AddWebJobsScriptHealthChecks_ThrowsOnNullBuilder()
+        {
+            IHealthChecksBuilder builder = null;
+            Action act = () => HealthCheckExtensions.AddWebJobsScriptHealthChecks(builder);
+            act.Should().Throw<ArgumentNullException>().WithParameterName("builder");
+        }
+
+        [Fact]
+        public void AddWebHostHealthCheck_ThrowsOnNullBuilder()
+        {
+            IHealthChecksBuilder builder = null;
+            Action act = () => HealthCheckExtensions.AddWebHostHealthCheck(builder);
+            act.Should().Throw<ArgumentNullException>().WithParameterName("builder");
+        }
+
+        [Fact]
+        public void AddScriptHostHealthCheck_ThrowsOnNullBuilder()
+        {
+            IHealthChecksBuilder builder = null;
+            Action act = () => HealthCheckExtensions.AddScriptHostHealthCheck(builder);
+            act.Should().Throw<ArgumentNullException>().WithParameterName("builder");
+        }
+
+        [Fact]
+        public void AddWebJobsScriptHealthChecks_RegistersBothHealthChecks()
+        {
+            // arrange
+            Mock<IHealthChecksBuilder> builder = new(MockBehavior.Strict);
+            builder.Setup(b => b.Add(It.IsAny<HealthCheckRegistration>())).Returns(builder.Object);
+
+            // act
+            IHealthChecksBuilder returned = builder.Object.AddWebJobsScriptHealthChecks();
+
+            // assert
+            returned.Should().BeSameAs(builder.Object);
+            builder.Verify(b => b.Add(IsRegistration<WebHostHealthCheck>(
+                HealthCheckNames.WebHostLifeCycle, HealthCheckTags.Liveness)),
+                Times.Once);
+            builder.Verify(b => b.Add(IsRegistration<ScriptHostHealthCheck>(
+                HealthCheckNames.ScriptHostLifeCycle, HealthCheckTags.Readiness)),
+                Times.Once);
+            builder.VerifyNoOtherCalls();
+        }
+
+        [Fact]
+        public void AddWebHostHealthCheck_RegistersWebHostHealthCheck()
+        {
+            // arrange
+            Mock<IHealthChecksBuilder> builder = new(MockBehavior.Strict);
+            builder.Setup(b => b.Add(It.IsAny<HealthCheckRegistration>())).Returns(builder.Object)
+                .Callback((HealthCheckRegistration registration) =>
+                {
+                    Type r = registration.Factory.GetMethodInfo().ReturnType;
+                });
+
+            // act
+            IHealthChecksBuilder returned = builder.Object.AddWebHostHealthCheck();
+
+            // assert
+            returned.Should().BeSameAs(builder.Object);
+            builder.Verify(b => b.Add(IsRegistration<WebHostHealthCheck>(
+                HealthCheckNames.WebHostLifeCycle, HealthCheckTags.Liveness)),
+                Times.Once);
+            builder.VerifyNoOtherCalls();
+        }
+
+        [Fact]
+        public void AddScriptHostHealthCheck_RegistersScriptHostHealthCheck()
+        {
+            // arrange
+            Mock<IHealthChecksBuilder> builder = new(MockBehavior.Strict);
+            builder.Setup(b => b.Add(It.IsAny<HealthCheckRegistration>())).Returns(builder.Object);
+
+            // act
+            IHealthChecksBuilder returned = builder.Object.AddScriptHostHealthCheck();
+
+            // assert
+            returned.Should().BeSameAs(builder.Object);
+            builder.Verify(b => b.Add(IsRegistration<ScriptHostHealthCheck>(
+                HealthCheckNames.ScriptHostLifeCycle, HealthCheckTags.Readiness)),
+                Times.Once);
+            builder.VerifyNoOtherCalls();
+        }
+
+        private static HealthCheckRegistration IsRegistration<T>(string name, string tag)
+            where T : IHealthCheck
+        {
+            static bool IsType(HealthCheckRegistration registration)
+            {
+                if (registration.Factory is not { } factory)
+                {
+                    return false;
+                }
+
+                return factory.GetMethodInfo().ReturnType == typeof(T);
+            }
+
+            return Match.Create<HealthCheckRegistration>(r =>
+            {
+                return r.Name == name && r.Tags.Contains(tag) && IsType(r);
+            });
+        }
+    }
+}

test/WebJobs.Script.Tests/Diagnostics/HealthChecks/ScriptHostHealthCheckTests.cs

@@ -3,7 +3,7 @@
 
 using System;
 using System.Threading.Tasks;
-using FluentAssertions;
+using AwesomeAssertions;
 using Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks;
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using Moq;

test/WebJobs.Script.Tests/Diagnostics/HealthChecks/WebHostHealthCheckTests.cs

@@ -3,7 +3,7 @@
 
 using System.Threading;
 using System.Threading.Tasks;
-using FluentAssertions;
+using AwesomeAssertions;
 using Microsoft.Azure.WebJobs.Script.Diagnostics.HealthChecks;
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using Microsoft.Extensions.Hosting;

test/WebJobs.Script.Tests/Diagnostics/OpenTelemetry/OpenTelemetryConfigurationExtensionsTests.cs

@@ -6,9 +6,9 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
+using AwesomeAssertions;
 using Azure.Identity;
 using Azure.Monitor.OpenTelemetry.Exporter;
-using FluentAssertions;
 using Microsoft.ApplicationInsights;
 using Microsoft.ApplicationInsights.Extensibility;
 using Microsoft.Azure.WebJobs.Script.Configuration;

test/WebJobs.Script.Tests/Middleware/AppServiceHeaderFixupMiddlewareTests.cs

@@ -2,7 +2,7 @@
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
 using System.Threading.Tasks;
-using FluentAssertions;
+using AwesomeAssertions;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Azure.WebJobs.Script.WebHost.Middleware;
 using Microsoft.Extensions.Primitives;

test/WebJobs.Script.Tests/WebJobs.Script.Tests.csproj

@@ -21,13 +21,13 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="AwesomeAssertions" Version="9.1.0" />
     <PackageReference Include="Microsoft.ApplicationInsights" Version="2.22.0" />
     <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.22.0" />
     <PackageReference Include="Microsoft.ApplicationInsights.DependencyCollector" Version="2.22.0" />
     <PackageReference Include="Microsoft.ApplicationInsights.WindowsServer" Version="2.22.0" />
     <PackageReference Include="Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel" Version="2.22.0" />
     <PackageReference Include="appinsights.testlogger" Version="1.0.0" />
-    <PackageReference Include="FluentAssertions" Version="5.9.0" />
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Diagnostics.Testing" Version="8.1.0" />
     <PackageReference Include="Microsoft.Azure.Functions.PythonWorker" Version="4.38.0" />