WaitFor for MongoDB (health checks)

playground/mongo/Mongo.AppHost/Program.cs

@@ -9,7 +9,7 @@
 
 builder.AddProject<Projects.Mongo_ApiService>("api")
        .WithExternalHttpEndpoints()
-       .WithReference(db);
+       .WithReference(db).WaitFor(db);
 
 #if !SKIP_DASHBOARD_REFERENCE
 // This project is only added in playground projects to support development/debugging

src/Aspire.Hosting.MongoDB/Aspire.Hosting.MongoDB.csproj

@@ -6,6 +6,7 @@
     <PackageTags>aspire integration hosting MongoDB</PackageTags>
     <PackageIconFullPath>$(SharedDir)MongoDB_300px.png</PackageIconFullPath>
     <Description>MongoDB support for .NET Aspire.</Description>
+    <NoWarn>$(NoWarn);CS8002</NoWarn> <!-- MongoDB.Driver.Core.Extensions.DiagnosticSources and AspNetCore.HealthChecks.MongoDb packages are not signed -->
   </PropertyGroup>
 
   <PropertyGroup>
@@ -20,4 +21,8 @@
   <ItemGroup>
     <ProjectReference Include="..\Aspire.Hosting\Aspire.Hosting.csproj" />
   </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="AspNetCore.HealthChecks.MongoDb" />
+  </ItemGroup>
 </Project>

src/Aspire.Hosting.MongoDB/MongoDBBuilderExtensions.cs

@@ -4,6 +4,7 @@
 using Aspire.Hosting.ApplicationModel;
 using Aspire.Hosting.MongoDB;
 using Aspire.Hosting.Utils;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace Aspire.Hosting;
 
@@ -29,11 +30,27 @@ public static IResourceBuilder<MongoDBServerResource> AddMongoDB(this IDistribut
 
         var mongoDBContainer = new MongoDBServerResource(name);
 
+        string? connectionString = null;
+
+        builder.Eventing.Subscribe<ConnectionStringAvailableEvent>(mongoDBContainer, async (@event, ct) =>
+        {
+            connectionString = await mongoDBContainer.ConnectionStringExpression.GetValueAsync(ct).ConfigureAwait(false);
+
+            if (connectionString == null)
+            {
+                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{mongoDBContainer.Name}' resource but the connection string was null.");
+            }
+        });
+
+        var healthCheckKey = $"{name}_check";
+        builder.Services.AddHealthChecks().AddMongoDb(sp => connectionString ?? throw new InvalidOperationException("Connection string is unavailable"), name: healthCheckKey);
+
         return builder
             .AddResource(mongoDBContainer)
             .WithEndpoint(port: port, targetPort: DefaultContainerPort, name: MongoDBServerResource.PrimaryEndpointName)
             .WithImage(MongoDBContainerImageTags.Image, MongoDBContainerImageTags.Tag)
-            .WithImageRegistry(MongoDBContainerImageTags.Registry);
+            .WithImageRegistry(MongoDBContainerImageTags.Registry)
+            .WithHealthCheck(healthCheckKey);
     }
 
     /// <summary>

src/Aspire.Hosting.PostgreSQL/PostgresBuilderExtensions.cs

@@ -56,7 +56,7 @@ public static IResourceBuilder<PostgresServerResource> AddPostgres(this IDistrib
 
             if (connectionString == null)
             {
-                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{postgresServer}' resource but the connection string was null.");
+                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{postgresServer.Name}' resource but the connection string was null.");
             }
 
             var lookup = builder.Resources.OfType<PostgresDatabaseResource>().ToDictionary(d => d.Name);

src/Aspire.Hosting.Redis/RedisBuilderExtensions.cs

@@ -47,7 +47,7 @@ public static IResourceBuilder<RedisResource> AddRedis(this IDistributedApplicat
 
             if (connectionString == null)
             {
-                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{redis}' resource but the connection string was null.");
+                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{redis.Name}' resource but the connection string was null.");
             }
         });
 

src/Aspire.Hosting.SqlServer/SqlServerBuilderExtensions.cs

@@ -38,7 +38,7 @@ public static IResourceBuilder<SqlServerServerResource> AddSqlServer(this IDistr
 
             if (connectionString == null)
             {
-                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{sqlServer}' resource but the connection string was null.");
+                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{sqlServer.Name}' resource but the connection string was null.");
             }
 
             var lookup = builder.Resources.OfType<SqlServerDatabaseResource>().ToDictionary(d => d.Name);

tests/Aspire.Hosting.MongoDB.Tests/MongoDbFunctionalTests.cs

@@ -11,6 +11,8 @@
 using Xunit;
 using Xunit.Abstractions;
 using Polly;
+using Aspire.Hosting.ApplicationModel;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
 
 namespace Aspire.Hosting.MongoDB.Tests;
 
@@ -26,6 +28,45 @@ public class MongoDbFunctionalTests(ITestOutputHelper testOutputHelper)
             new() { Name = "Schindler's List"},
         ];
 
+    [Fact]
+    [RequiresDocker]
+    public async Task VerifyWaitForOnMongoBlocksDependentResources()
+    {
+        var cts = new CancellationTokenSource(TimeSpan.FromMinutes(3));
+        using var builder = TestDistributedApplicationBuilder.CreateWithTestContainerRegistry(testOutputHelper);
+
+        var healthCheckTcs = new TaskCompletionSource<HealthCheckResult>();
+        builder.Services.AddHealthChecks().AddAsyncCheck("blocking_check", () =>
+        {
+            return healthCheckTcs.Task;
+        });
+
+        var resource = builder.AddMongoDB("resource")
+                           .WithHealthCheck("blocking_check");
+
+        var dependentResource = builder.AddMongoDB("dependentresource")
+                                       .WaitFor(resource);
+
+        using var app = builder.Build();
+
+        var pendingStart = app.StartAsync(cts.Token);
+
+        var rns = app.Services.GetRequiredService<ResourceNotificationService>();
+
+        await rns.WaitForResourceAsync(resource.Resource.Name, KnownResourceStates.Running, cts.Token);
+
+        await rns.WaitForResourceAsync(dependentResource.Resource.Name, KnownResourceStates.Waiting, cts.Token);
+
+        healthCheckTcs.SetResult(HealthCheckResult.Healthy());
+
+        await rns.WaitForResourceAsync(resource.Resource.Name, (re => re.Snapshot.HealthStatus == HealthStatus.Healthy), cts.Token);
+
+        await rns.WaitForResourceAsync(dependentResource.Resource.Name, KnownResourceStates.Running, cts.Token);
+
+        await pendingStart;
+        await app.StopAsync();
+    }
+
     [Fact]
     [RequiresDocker]
     public async Task VerifyMongoDBResource()