Add status classes and tests

NuGet.Server.Common.sln

@@ -62,6 +62,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NuGet.Services.Sql", "src\N
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NuGet.Services.Sql.Tests", "tests\NuGet.Services.Sql.Tests\NuGet.Services.Sql.Tests.csproj", "{FA2B3447-7242-495F-A8E1-D94181C0C9A5}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NuGet.Services.Status", "src\NuGet.Services.Status\NuGet.Services.Status.csproj", "{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NuGet.Services.Status.Tests", "tests\NuGet.Services.Status.Tests\NuGet.Services.Status.Tests.csproj", "{EA54BC71-F9AD-4863-8DC6-8CC41776C881}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -168,6 +172,14 @@ Global
 		{FA2B3447-7242-495F-A8E1-D94181C0C9A5}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{FA2B3447-7242-495F-A8E1-D94181C0C9A5}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{FA2B3447-7242-495F-A8E1-D94181C0C9A5}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056}.Release|Any CPU.Build.0 = Release|Any CPU
+		{EA54BC71-F9AD-4863-8DC6-8CC41776C881}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EA54BC71-F9AD-4863-8DC6-8CC41776C881}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EA54BC71-F9AD-4863-8DC6-8CC41776C881}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EA54BC71-F9AD-4863-8DC6-8CC41776C881}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -198,6 +210,8 @@ Global
 		{E29F54DF-DFB8-4E27-940D-21ECCB9B6FC1} = {7783A106-0F4C-4055-9AB4-413FB2C7B8F0}
 		{F5121B0A-669F-48BD-86DC-27C546D1A825} = {8415FED7-1BED-4227-8B4F-BB7C24E041CD}
 		{FA2B3447-7242-495F-A8E1-D94181C0C9A5} = {7783A106-0F4C-4055-9AB4-413FB2C7B8F0}
+		{D3AB8DBD-EF83-41A5-AF25-0A7E7FACC056} = {8415FED7-1BED-4227-8B4F-BB7C24E041CD}
+		{EA54BC71-F9AD-4863-8DC6-8CC41776C881} = {7783A106-0F4C-4055-9AB4-413FB2C7B8F0}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {AA413DB0-5475-4B5D-A3AF-6323DA8D538B}

build.ps1

@@ -72,7 +72,8 @@ Invoke-BuildStep 'Set version metadata in AssemblyInfo.cs' { `
             "$PSScriptRoot\src\NuGet.Services.ServiceBus\Properties\AssemblyInfo.g.cs", `
             "$PSScriptRoot\src\NuGet.Services.Validation\Properties\AssemblyInfo.g.cs", `
             "$PSScriptRoot\src\NuGet.Services.Validation.Issues\Properties\AssemblyInfo.g.cs", `
-            "$PSScriptRoot\src\NuGet.Services.Sql\Properties\AssemblyInfo.g.cs"
+            "$PSScriptRoot\src\NuGet.Services.Sql\Properties\AssemblyInfo.g.cs", `
+            "$PSScriptRoot\src\NuGet.Services.Status\Properties\AssemblyInfo.g.cs"
 
         $versionMetadata | ForEach-Object {
             Set-VersionInfo -Path $_ -Version $SimpleVersion -Branch $Branch -Commit $CommitSHA
@@ -105,7 +106,8 @@ Invoke-BuildStep 'Creating artifacts' { `
             "src\NuGet.Services.ServiceBus\NuGet.Services.ServiceBus.csproj", `
             "src\NuGet.Services.Validation\NuGet.Services.Validation.csproj", `
             "src\NuGet.Services.Validation.Issues\NuGet.Services.Validation.Issues.csproj", `
-            "src\NuGet.Services.Sql\NuGet.Services.Sql.csproj"
+            "src\NuGet.Services.Sql\NuGet.Services.Sql.csproj", `
+            "src\NuGet.Services.Status\NuGet.Services.Status.csproj"
 
         $projects | ForEach-Object {
             New-Package (Join-Path $PSScriptRoot $_) -Configuration $Configuration -Symbols -IncludeReferencedProjects -MSBuildVersion "15"

src/NuGet.Services.Status/Component.cs

@@ -0,0 +1,36 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NuGet.Services.Status
+{
+    /// <summary>
+    /// Default implementation of <see cref="IComponent"/>.
+    /// </summary>
+    public abstract class Component : ReadOnlyComponent, IComponent
+    {
+        public new abstract ComponentStatus Status { get; set; }
+        public new IEnumerable<IComponent> SubComponents { get; }
+
+        public Component(
+            string name,
+            string description)
+            : base(name, description)
+        {
+            SubComponents = Enumerable.Empty<IComponent>();
+        }
+
+        public Component(
+            string name,
+            string description,
+            IEnumerable<IComponent> subComponents)
+            : base(name, description, subComponents)
+        {
+            SubComponents = subComponents?.Select(s => new ComponentWrapper(s, this)).ToList()
+                ?? throw new ArgumentNullException(nameof(subComponents));
+        }
+    }
+}

src/NuGet.Services.Status/ComponentStatus.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace NuGet.Services.Status
+{
+    /// <summary>
+    /// Describes whether or not a <see cref="IReadOnlyComponent"/> is performing as expected.
+    /// </summary>
+    public enum ComponentStatus
+    {
+        /// <summary>
+        /// The <see cref="IReadOnlyComponent"/> is performing as expected.
+        /// </summary>
+        Up,
+
+        /// <summary>
+        /// Some portion of the <see cref="IReadOnlyComponent"/> is not performing as expected.
+        /// </summary>
+        Degraded,
+
+        /// <summary>
+        /// The <see cref="IReadOnlyComponent"/> is completely unfunctional.
+        /// </summary>
+        Down
+    }
+}

src/NuGet.Services.Status/ComponentUtility.cs

@@ -0,0 +1,86 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NuGet.Services.Status
+{
+    public static class ComponentUtility
+    {
+        /// <summary>
+        /// Concatenates a set of <see cref="IReadOnlyComponent.Name"/>s into a <see cref="IReadOnlyComponent.Path"/>.
+        /// </summary>
+        public static string GetPath(params string[] componentNames)
+        {
+            componentNames = componentNames ?? throw new ArgumentNullException(nameof(componentNames));
+
+            return string.Join(Constants.ComponentPathDivider.ToString(), componentNames);
+        }
+
+        /// <summary>
+        /// Gets the subcomponent of <paramref name="component"/> with <see cref="IReadOnlyComponent.Path"/> <paramref name="path"/>.
+        /// If none exists, returns <c>null</c>.
+        /// </summary>
+        public static TComponent GetByPath<TComponent>(this TComponent component, string path)
+            where TComponent : class, IReadOnlyComponent, IComponentRoot<TComponent>
+        {
+            if (path == null)
+            {
+                return null;
+            }
+
+            var componentNames = path.Split(Constants.ComponentPathDivider);
+            return component.GetByNames(componentNames);
+        }
+
+        /// <summary>
+        /// Gets the subcomponent of <paramref name="component"/> by iterating its subcomponents in the order of <paramref name="componentNames"/>.
+        /// If none exists, returns <c>null</c>.
+        /// </summary>
+        public static TComponent GetByNames<TComponent>(this TComponent component, params string[] componentNames)
+            where TComponent : class, IReadOnlyComponent, IComponentRoot<TComponent>
+        {
+            if (component == null)
+            {
+                return null;
+            }
+
+            if (componentNames == null)
+            {
+                return null;
+            }
+
+            TComponent currentComponent = null;
+            IComponentRoot<TComponent> currentRoot = new GetByNamesHelper<TComponent>(component);
+            foreach (var componentName in componentNames)
+            {
+                currentComponent = currentRoot.SubComponents.FirstOrDefault(c => c.Name == componentName);
+
+                if (currentComponent == null)
+                {
+                    break;
+                }
+
+                currentRoot = currentComponent;
+            }
+
+            return currentComponent;
+        }
+
+        /// <remarks>
+        /// Dummy implementation of <see cref="IComponentRoot{TComponent}"/> used by <see cref="GetByNames{TComponent}(TComponent, string[])"/>.
+        /// </remarks>
+        private class GetByNamesHelper<TComponent> : IComponentRoot<TComponent>
+            where TComponent : IReadOnlyComponent
+        {
+            public IEnumerable<TComponent> SubComponents { get; }
+
+            public GetByNamesHelper(TComponent root)
+            {
+                SubComponents = new[] { root };
+            }
+        }
+    }
+}

src/NuGet.Services.Status/ComponentWrapper.cs

@@ -0,0 +1,29 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NuGet.Services.Status
+{
+    /// <summary>
+    /// Wrapper class for <see cref="IComponent"/> that sets <see cref="IReadOnlyComponent.Path"/> as expected.
+    /// </summary>
+    internal class ComponentWrapper : ReadOnlyComponentWrapper, IComponent
+    {
+        private readonly IComponent _component;
+        private readonly IComponent _parent;
+
+        public new ComponentStatus Status { get { return _component.Status; } set { _component.Status = value; } }
+        public new IEnumerable<IComponent> SubComponents { get; }
+
+        public ComponentWrapper(IComponent component, IComponent parent)
+            : base(component, parent)
+        {
+            _component = component;
+            _parent = parent;
+            SubComponents = _component.SubComponents?.Select(s => new ComponentWrapper(s, this)).ToList()
+                ?? Enumerable.Empty<IComponent>();
+        }
+    }
+}

src/NuGet.Services.Status/Constants.cs

@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace NuGet.Services.Status
+{
+    public static class Constants
+    {
+        /// <summary>
+        /// Used to construct <see cref="IReadOnlyComponent.Path"/>.
+        /// </summary>
+        /// <example>
+        /// Suppose C is a subcomponent of B which is a subcomponent of A.
+        /// The path of C is <code>"A" + ComponentPathDivider + "B" + ComponentPathDivider + "C"</code>.
+        /// </example>
+        public static char ComponentPathDivider = '/';
+    }
+}

src/NuGet.Services.Status/Event.cs

@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace NuGet.Services.Status
+{
+    public class Event : IEvent
+    {
+        public string AffectedComponentPath { get; }
+        public ComponentStatus AffectedComponentStatus { get; }
+        public DateTime StartTime { get; }
+        public DateTime? EndTime { get; }
+        public IEnumerable<IMessage> Messages { get; }
+
+        public Event(
+            string affectedComponentPath,
+            ComponentStatus affectedComponentStatus,
+            DateTime startTime,
+            DateTime? endTime,
+            IEnumerable<IMessage> messages)
+        {
+            AffectedComponentPath = affectedComponentPath;
+            AffectedComponentStatus = affectedComponentStatus;
+            StartTime = startTime;
+            EndTime = endTime;
+            Messages = messages;
+        }
+
+        [JsonConstructor]
+        public Event(
+            string affectedComponentPath,
+            ComponentStatus affectedComponentStatus, 
+            DateTime startTime, 
+            DateTime? endTime, 
+            IEnumerable<Message> messages)
+            : this(
+                  affectedComponentPath, 
+                  affectedComponentStatus, 
+                  startTime, 
+                  endTime, 
+                  (IEnumerable<IMessage>)messages)
+        {
+        }
+    }
+}

src/NuGet.Services.Status/IComponent.cs

@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace NuGet.Services.Status
+{
+    /// <summary>
+    /// A writable <see cref="IReadOnlyComponent"/> that allows setting its status.
+    /// </summary>
+    public interface IComponent : IReadOnlyComponent, IComponentRoot<IComponent>
+    {
+        /// <summary>
+        /// The status of this part of the service.
+        /// </summary>
+        new ComponentStatus Status { get; set; }
+
+        /// <summary>
+        /// A list of writable subcomponents that make up this part of the service.
+        /// </summary>
+        new IEnumerable<IComponent> SubComponents { get; }
+    }
+}

src/NuGet.Services.Status/IComponentRoot.cs

@@ -0,0 +1,13 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace NuGet.Services.Status
+{
+    public interface IComponentRoot<out TComponent> 
+        where TComponent : IReadOnlyComponent
+    {
+        IEnumerable<TComponent> SubComponents { get; }
+    }
+}

src/NuGet.Services.Status/IEvent.cs

@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+
+namespace NuGet.Services.Status
+{
+    /// <summary>
+    /// Represents an event affecting a <see cref="IReadOnlyComponent"/>.
+    /// </summary>
+    public interface IEvent
+    {
+        /// <summary>
+        /// The <see cref="IReadOnlyComponent.Path"/> of the <see cref="IReadOnlyComponent"/> affected.
+        /// </summary>
+        string AffectedComponentPath { get; }
+
+        /// <summary>
+        /// The <see cref="IReadOnlyComponent.Status"/> of the <see cref="IReadOnlyComponent"/> affected.
+        /// </summary>
+        ComponentStatus AffectedComponentStatus { get; }
+
+        /// <summary>
+        /// When the event began.
+        /// </summary>
+        DateTime StartTime { get; }
+
+        /// <summary>
+        /// When the event ended, or <c>null</c> if the event is still active.
+        /// </summary>
+        DateTime? EndTime { get; }
+
+        /// <summary>
+        /// A set of <see cref="IMessage"/>s related to this event.
+        /// </summary>
+        IEnumerable<IMessage> Messages { get; }
+    }
+}