Add file health check similar to folder health check (#2027)

src/HealthChecks.System/DependencyInjection/SystemHealthCheckBuilderExtensions.cs

@@ -16,6 +16,7 @@ public static class SystemHealthCheckBuilderExtensions
     private const string PROCESS_ALLOCATED_MEMORY = "process_allocated_memory";
     private const string WINDOWS_SERVICE_NAME = "windowsservice";
     private const string FOLDER_NAME = "folder";
+    private const string FILE_NAME = "file";
 
     /// <summary>
     /// Add a health check for disk storage.
@@ -248,7 +249,7 @@ public static IHealthChecksBuilder AddWindowsServiceHealthCheck(
     /// Add a healthcheck that allows to check for the existence of one or more folders.
     /// </summary>
     /// <param name="builder">The <see cref="IHealthChecksBuilder"/>.</param>
-    /// <param name="setup">The action method to configure the health check parameters.</param>
+    /// <param name="setup">Delegate for configuring the health check. Optional.</param>
     /// <param name="name">The health check name. Optional. If <c>null</c> the type name 'folder' will be used for the name.</param>
     /// <param name="failureStatus">
     /// The <see cref="HealthStatus"/> that should be reported when the health check fails. Optional. If <c>null</c> then
@@ -275,4 +276,62 @@ public static IHealthChecksBuilder AddFolder(
             tags,
             timeout));
     }
+
+    /// <summary>
+    /// Add a healthcheck that allows to check for the existence of one or more files.
+    /// </summary>
+    /// <param name="builder">The <see cref="IHealthChecksBuilder"/>.</param>
+    /// <param name="setup">Delegate for configuring the health check. Optional.</param>
+    /// <param name="name">The health check name. Optional. If <c>null</c> the type name 'file' will be used for the name.</param>
+    /// <param name="failureStatus">
+    /// The <see cref="HealthStatus"/> that should be reported when the health check fails. Optional. If <c>null</c> then
+    /// the default status of <see cref="HealthStatus.Unhealthy"/> will be reported.
+    /// </param>
+    /// <param name="tags">A list of tags that can be used to filter sets of health checks. Optional.</param>
+    /// <param name="timeout">An optional <see cref="TimeSpan"/> representing the timeout of the check.</param>
+    /// <returns>The specified <paramref name="builder"/>.</returns>
+    public static IHealthChecksBuilder AddFile(
+        this IHealthChecksBuilder builder,
+        Action<FileHealthCheckOptions>? setup,
+        string? name = default,
+        HealthStatus? failureStatus = default,
+        IEnumerable<string>? tags = default,
+        TimeSpan? timeout = default)
+    {
+        return AddFile(builder, (_, options) => setup?.Invoke(options), name, failureStatus, tags, timeout);
+    }
+
+    /// <summary>
+    /// Add a healthcheck that allows to check for the existence of one or more files.
+    /// </summary>
+    /// <param name="builder">The <see cref="IHealthChecksBuilder"/>.</param>
+    /// <param name="setup">The action method to configure the health check parameters.</param>
+    /// <param name="name">The health check name. Optional. If <c>null</c> the type name 'file' will be used for the name.</param>
+    /// <param name="failureStatus">
+    /// The <see cref="HealthStatus"/> that should be reported when the health check fails. Optional. If <c>null</c> then
+    /// the default status of <see cref="HealthStatus.Unhealthy"/> will be reported.
+    /// </param>
+    /// <param name="tags">A list of tags that can be used to filter sets of health checks. Optional.</param>
+    /// <param name="timeout">An optional <see cref="TimeSpan"/> representing the timeout of the check.</param>
+    /// <returns>The specified <paramref name="builder"/>.</returns>
+    public static IHealthChecksBuilder AddFile(
+        this IHealthChecksBuilder builder,
+        Action<IServiceProvider, FileHealthCheckOptions>? setup,
+        string? name = default,
+        HealthStatus? failureStatus = default,
+        IEnumerable<string>? tags = default,
+        TimeSpan? timeout = default)
+    {
+        return builder.Add(new HealthCheckRegistration(
+            name ?? FILE_NAME,
+            sp =>
+            {
+                var options = new FileHealthCheckOptions();
+                setup?.Invoke(sp, options);
+                return new FileHealthCheck(options);
+            },
+            failureStatus,
+            tags,
+            timeout));
+    }
 }

src/HealthChecks.System/FileHealthCheck.cs

@@ -0,0 +1,41 @@
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace HealthChecks.System;
+
+public class FileHealthCheck : IHealthCheck
+{
+    private readonly FileHealthCheckOptions _fileOptions;
+
+    public FileHealthCheck(FileHealthCheckOptions fileOptions)
+    {
+        _fileOptions = fileOptions;
+    }
+
+    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            List<string> errorList = new();
+            foreach (string file in _fileOptions.Files)
+            {
+                if (!string.IsNullOrEmpty(file))
+                {
+                    if (!File.Exists(file))
+                    {
+                        errorList.Add($"File {file} does not exist.");
+                        if (!_fileOptions.CheckAllFiles)
+                        {
+                            break;
+                        }
+                    }
+                }
+            }
+
+            return Task.FromResult(errorList.GetHealthState(context));
+        }
+        catch (Exception ex)
+        {
+            return Task.FromResult(new HealthCheckResult(context.Registration.FailureStatus, exception: ex));
+        }
+    }
+}

src/HealthChecks.System/FileHealthCheckOptions.cs

@@ -0,0 +1,19 @@
+namespace HealthChecks.System;
+
+public class FileHealthCheckOptions
+{
+    public List<string> Files { get; } = new();
+    public bool CheckAllFiles { get; set; }
+
+    public FileHealthCheckOptions AddFile(string file)
+    {
+        Files.Add(file);
+        return this;
+    }
+
+    public FileHealthCheckOptions WithCheckAllFiles()
+    {
+        CheckAllFiles = true;
+        return this;
+    }
+}

test/HealthChecks.System.Tests/Functional/FileHealthCheckTests.cs

@@ -0,0 +1,80 @@
+using System.Net;
+
+namespace HealthChecks.System.Tests.Functional;
+
+public class file_healthcheck_should
+{
+    [Fact]
+    public async Task be_healthy_if_file_is_available()
+    {
+        var webHostBuilder = new WebHostBuilder()
+           .ConfigureServices(services =>
+           {
+               services.AddHealthChecks()
+                   .AddFile(setup => setup.AddFile(Path.Combine(Directory.GetCurrentDirectory(), "HealthChecks.System.Tests.dll")), tags: new string[] { "file" });
+           })
+           .Configure(app =>
+           {
+               app.UseHealthChecks("/health", new HealthCheckOptions
+               {
+                   Predicate = r => r.Tags.Contains("file")
+               });
+           });
+
+        using var server = new TestServer(webHostBuilder);
+
+        using var response = await server.CreateRequest("/health").GetAsync().ConfigureAwait(false);
+
+        response.StatusCode.ShouldBe(HttpStatusCode.OK);
+    }
+
+    [Fact]
+    public async Task be_healthy_if_no_file_provided()
+    {
+        var webHostBuilder = new WebHostBuilder()
+           .ConfigureServices(services =>
+           {
+               services.AddHealthChecks()
+                   .AddFile(setup =>
+                   {
+                   }, tags: new string[] { "file" });
+           })
+           .Configure(app =>
+           {
+               app.UseHealthChecks("/health", new HealthCheckOptions
+               {
+                   Predicate = r => r.Tags.Contains("file")
+               });
+           });
+
+        using var server = new TestServer(webHostBuilder);
+
+        using var response = await server.CreateRequest("/health").GetAsync().ConfigureAwait(false);
+
+        response.StatusCode.ShouldBe(HttpStatusCode.OK);
+    }
+
+    [Fact]
+    public async Task be_unhealthy_if_file_is_not_available()
+    {
+        var webHostBuilder = new WebHostBuilder()
+            .ConfigureServices(services =>
+            {
+                services.AddHealthChecks()
+                    .AddFile(setup => setup.AddFile($"{Directory.GetCurrentDirectory()}/non-existing-file"), tags: new string[] { "file" });
+            })
+            .Configure(app =>
+            {
+                app.UseHealthChecks("/health", new HealthCheckOptions
+                {
+                    Predicate = r => r.Tags.Contains("file")
+                });
+            });
+
+        using var server = new TestServer(webHostBuilder);
+
+        using var response = await server.CreateRequest("/health").GetAsync().ConfigureAwait(false);
+
+        response.StatusCode.ShouldBe(HttpStatusCode.ServiceUnavailable);
+    }
+}

test/HealthChecks.System.Tests/HealthChecks.System.approved.txt

@@ -14,6 +14,19 @@ namespace HealthChecks.System
         public HealthChecks.System.DiskStorageOptions WithCheckAllDrives() { }
         public delegate string ErrorDescription(string driveName, long minimumFreeMegabytes, long? actualFreeMegabytes);
     }
+    public class FileHealthCheck : Microsoft.Extensions.Diagnostics.HealthChecks.IHealthCheck
+    {
+        public FileHealthCheck(HealthChecks.System.FileHealthCheckOptions fileOptions) { }
+        public System.Threading.Tasks.Task<Microsoft.Extensions.Diagnostics.HealthChecks.HealthCheckResult> CheckHealthAsync(Microsoft.Extensions.Diagnostics.HealthChecks.HealthCheckContext context, System.Threading.CancellationToken cancellationToken = default) { }
+    }
+    public class FileHealthCheckOptions
+    {
+        public FileHealthCheckOptions() { }
+        public bool CheckAllFiles { get; set; }
+        public System.Collections.Generic.List<string> Files { get; }
+        public HealthChecks.System.FileHealthCheckOptions AddFile(string file) { }
+        public HealthChecks.System.FileHealthCheckOptions WithCheckAllFiles() { }
+    }
     public class FolderHealthCheck : Microsoft.Extensions.Diagnostics.HealthChecks.IHealthCheck
     {
         public FolderHealthCheck(HealthChecks.System.FolderHealthCheckOptions folderOptions) { }
@@ -54,6 +67,8 @@ namespace Microsoft.Extensions.DependencyInjection
     public static class SystemHealthCheckBuilderExtensions
     {
         public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddDiskStorageHealthCheck(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, System.Action<HealthChecks.System.DiskStorageOptions>? setup, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }
+        public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddFile(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, System.Action<HealthChecks.System.FileHealthCheckOptions>? setup, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }
+        public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddFile(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, System.Action<System.IServiceProvider, HealthChecks.System.FileHealthCheckOptions>? setup, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }
         public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddFolder(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, System.Action<HealthChecks.System.FolderHealthCheckOptions>? setup, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }
         public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddPrivateMemoryHealthCheck(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, long maximumMemoryBytes, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }
         public static Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder AddProcessAllocatedMemoryHealthCheck(this Microsoft.Extensions.DependencyInjection.IHealthChecksBuilder builder, int maximumMegabytesAllocated, string? name = null, Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus? failureStatus = default, System.Collections.Generic.IEnumerable<string>? tags = null, System.TimeSpan? timeout = default) { }