Merge Add health check endpoint #45

src/DbUpdateService.cs

@@ -14,12 +14,14 @@ public class DbUpdateService : BackgroundService
     private readonly ILogger<DbUpdateService> logger;
     private readonly IConfiguration configuration;
     private readonly TimeOnly preferredTime;
+    private readonly DbUpdateServiceHealthCheck healthCheck;
 
-    public DbUpdateService(IServiceScopeFactory scopeFactory, ILogger<DbUpdateService> logger, IConfiguration configuration)
+    public DbUpdateService(IServiceScopeFactory scopeFactory, ILogger<DbUpdateService> logger, IConfiguration configuration, DbUpdateServiceHealthCheck healthCheck)
     {
         this.scopeFactory = scopeFactory;
         this.logger = logger;
         this.configuration = configuration;
+        this.healthCheck = healthCheck;
 
         preferredTime = new TimeOnly(1, 0);
     }
@@ -62,10 +64,13 @@ private async Task UpdateModelRepoDatabase()
                     logger.LogError("Updating ModelRepoDatabase aborted. Crawler could not parse any repository.");
                 }
             }
+
+            healthCheck.LastDbUpdateSuccessful = true;
         }
         catch (DbUpdateException ex)
         {
             logger.LogError(ex, "Unable to update ModelRepoDatabase");
+            healthCheck.LastDbUpdateSuccessful = false;
         }
     }
 

src/DbUpdateServiceHealthCheck.cs

@@ -0,0 +1,30 @@
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace ModelRepoBrowser;
+
+/// <summary>
+/// HealthCheck for <see cref="DbUpdateService"/>.
+/// Reports a degraded health if the last model repository database update exited with an exception.
+/// </summary>
+public class DbUpdateServiceHealthCheck : IHealthCheck
+{
+    private volatile bool lastDbUpdateSuccessful;
+
+    public bool LastDbUpdateSuccessful
+    {
+        get { return lastDbUpdateSuccessful; }
+        set { lastDbUpdateSuccessful = value; }
+    }
+
+    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
+    {
+        if (lastDbUpdateSuccessful)
+        {
+            return Task.FromResult(HealthCheckResult.Healthy());
+        }
+        else
+        {
+            return Task.FromResult(HealthCheckResult.Degraded());
+        }
+    }
+}

src/Program.cs

@@ -18,6 +18,12 @@
 
 builder.Services.AddTransient<IRepositoryCrawler, RepositoryCrawler>().AddHttpClient();
 builder.Services.AddHostedService<DbUpdateService>();
+builder.Services.AddSingleton<DbUpdateServiceHealthCheck>();
+
+builder.Services.AddHealthChecks()
+    .AddCheck<RepoBrowserDbHealthCheck>("RepoBrowserDbHealthCheck")
+    .AddCheck<DbUpdateServiceHealthCheck>("DbUpdateServiceHealthCheck");
+
 var app = builder.Build();
 
 if (!app.Environment.IsDevelopment())
@@ -29,6 +35,8 @@
 app.UseStaticFiles();
 app.UseRouting();
 
+app.MapHealthChecks("/health");
+
 app.MapControllerRoute(
     name: "default",
     pattern: "{controller}/{action=Index}/{id?}");

src/RepoBrowserDbHealthCheck.cs

@@ -0,0 +1,36 @@
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace ModelRepoBrowser;
+
+/// <summary>
+/// Health check for model repository database. Checks whether the database is accessible and contains data.
+/// </summary>
+public class RepoBrowserDbHealthCheck : IHealthCheck
+{
+    private readonly RepoBrowserContext repoBrowserContext;
+
+    public RepoBrowserDbHealthCheck(RepoBrowserContext context)
+    {
+        repoBrowserContext = context;
+    }
+
+    public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default(CancellationToken))
+    {
+        var canConnectToDb = await repoBrowserContext.Database.CanConnectAsync(cancellationToken).ConfigureAwait(false);
+        var dbContainsData = false;
+
+        if (canConnectToDb)
+        {
+            dbContainsData = repoBrowserContext.Models.Any() && repoBrowserContext.Repositories.Any() && repoBrowserContext.Catalogs.Any();
+        }
+
+        if (canConnectToDb && dbContainsData)
+        {
+            return HealthCheckResult.Healthy();
+        }
+        else
+        {
+            return HealthCheckResult.Unhealthy();
+        }
+    }
+}