feat: adopt shared ZB.MOM.WW.Health probes; add /healthz; canonical writer

src/ZB.MOM.WW.ScadaBridge.Host/Health/ActiveNodeHealthCheck.cs

@@ -1,45 +0,0 @@
-using Akka.Cluster;
-using Microsoft.Extensions.Diagnostics.HealthChecks;
-using ZB.MOM.WW.ScadaBridge.Host.Actors;
-
-namespace ZB.MOM.WW.ScadaBridge.Host.Health;
-
-/// <summary>
-/// Health check that returns healthy only if this node is the active (leader) node
-/// in the Akka.NET cluster. Used by Traefik to route traffic to the active node.
-/// </summary>
-public class ActiveNodeHealthCheck : IHealthCheck
-{
-    private readonly AkkaHostedService _akkaService;
-
-    /// <summary>Initializes a new <see cref="ActiveNodeHealthCheck"/> with the given Akka hosted service.</summary>
-    /// <param name="akkaService">The Akka hosted service providing access to the actor system and cluster state.</param>
-    public ActiveNodeHealthCheck(AkkaHostedService akkaService)
-    {
-        _akkaService = akkaService;
-    }
-
-    /// <summary>Returns healthy if this node is the cluster leader (active node); otherwise returns unhealthy.</summary>
-    /// <param name="context">Health check context providing registration details.</param>
-    /// <param name="cancellationToken">Cancellation token.</param>
-    public Task<HealthCheckResult> CheckHealthAsync(
-        HealthCheckContext context,
-        CancellationToken cancellationToken = default)
-    {
-        var system = _akkaService.ActorSystem;
-        if (system == null)
-            return Task.FromResult(HealthCheckResult.Unhealthy("ActorSystem not yet available."));
-
-        var cluster = Cluster.Get(system);
-        var self = cluster.SelfMember;
-
-        if (self.Status != MemberStatus.Up)
-            return Task.FromResult(HealthCheckResult.Unhealthy($"Node not Up (status: {self.Status})."));
-
-        var leader = cluster.State.Leader;
-        if (leader != null && leader == self.Address)
-            return Task.FromResult(HealthCheckResult.Healthy("Active node (cluster leader)."));
-
-        return Task.FromResult(HealthCheckResult.Unhealthy("Standby node (not cluster leader)."));
-    }
-}

src/ZB.MOM.WW.ScadaBridge.Host/Health/AkkaClusterHealthCheck.cs

@@ -1,52 +0,0 @@
-using Akka.Cluster;
-using Microsoft.Extensions.Diagnostics.HealthChecks;
-using ZB.MOM.WW.ScadaBridge.Host.Actors;
-
-namespace ZB.MOM.WW.ScadaBridge.Host.Health;
-
-/// <summary>
-/// Health check that verifies this node is an active member of the Akka.NET cluster.
-/// Returns healthy only if the node's self-member status is Up or Joining.
-/// </summary>
-public class AkkaClusterHealthCheck : IHealthCheck
-{
-    private readonly AkkaHostedService _akkaService;
-
-    /// <summary>
-    /// Initializes the health check with the Akka hosted service.
-    /// </summary>
-    /// <param name="akkaService">The hosted service providing access to the Akka actor system.</param>
-    public AkkaClusterHealthCheck(AkkaHostedService akkaService)
-    {
-        _akkaService = akkaService;
-    }
-
-    /// <summary>
-    /// Checks that this node is an active member of the Akka.NET cluster.
-    /// </summary>
-    /// <param name="context">Health check context.</param>
-    /// <param name="cancellationToken">Cancellation token.</param>
-    public Task<HealthCheckResult> CheckHealthAsync(
-        HealthCheckContext context,
-        CancellationToken cancellationToken = default)
-    {
-        var system = _akkaService.ActorSystem;
-        if (system == null)
-            return Task.FromResult(HealthCheckResult.Degraded("ActorSystem not yet available."));
-
-        var cluster = Cluster.Get(system);
-        var status = cluster.SelfMember.Status;
-
-        var result = status switch
-        {
-            MemberStatus.Up or MemberStatus.Joining =>
-                HealthCheckResult.Healthy($"Akka cluster member status: {status}"),
-            MemberStatus.Leaving or MemberStatus.Exiting =>
-                HealthCheckResult.Degraded($"Akka cluster member status: {status}"),
-            _ =>
-                HealthCheckResult.Unhealthy($"Akka cluster member status: {status}")
-        };
-
-        return Task.FromResult(result);
-    }
-}

src/ZB.MOM.WW.ScadaBridge.Host/Health/DatabaseHealthCheck.cs

@@ -1,43 +0,0 @@
-using Microsoft.Extensions.Diagnostics.HealthChecks;
-using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase;
-
-namespace ZB.MOM.WW.ScadaBridge.Host.Health;
-
-/// <summary>
-/// Health check that verifies database connectivity for Central nodes.
-/// </summary>
-public class DatabaseHealthCheck : IHealthCheck
-{
-    private readonly ScadaBridgeDbContext _dbContext;
-
-    /// <summary>
-    /// Initializes a new <see cref="DatabaseHealthCheck"/>.
-    /// </summary>
-    /// <param name="dbContext">The EF Core database context used to test connectivity.</param>
-    public DatabaseHealthCheck(ScadaBridgeDbContext dbContext)
-    {
-        _dbContext = dbContext;
-    }
-
-    /// <summary>
-    /// Checks database connectivity by attempting to open a connection.
-    /// </summary>
-    /// <param name="context">Health check context providing failure status information.</param>
-    /// <param name="cancellationToken">Cancellation token for the check.</param>
-    public async Task<HealthCheckResult> CheckHealthAsync(
-        HealthCheckContext context,
-        CancellationToken cancellationToken = default)
-    {
-        try
-        {
-            var canConnect = await _dbContext.Database.CanConnectAsync(cancellationToken);
-            return canConnect
-                ? HealthCheckResult.Healthy("Database connection is available.")
-                : HealthCheckResult.Unhealthy("Database connection failed.");
-        }
-        catch (Exception ex)
-        {
-            return HealthCheckResult.Unhealthy("Database connection failed.", ex);
-        }
-    }
-}

src/ZB.MOM.WW.ScadaBridge.Host/Program.cs

@@ -1,5 +1,6 @@
-using HealthChecks.UI.Client;
+using ZB.MOM.WW.Health;
-using Microsoft.AspNetCore.Diagnostics.HealthChecks;
+using ZB.MOM.WW.Health.Akka;
+using ZB.MOM.WW.Health.EntityFrameworkCore;
 using ZB.MOM.WW.ScadaBridge.AuditLog;
 using ZB.MOM.WW.ScadaBridge.CentralUI;
 using ZB.MOM.WW.ScadaBridge.ClusterInfrastructure;
@@ -110,11 +111,25 @@ try
             ?? throw new InvalidOperationException("ScadaBridge:Database:ConfigurationDb connection string is required for Central role.");
         builder.Services.AddConfigurationDatabase(configDbConnectionString);
 
-        // WP-12: Health checks for readiness gating
+        // WP-12: Health checks for readiness gating — shared ZB.MOM.WW.Health probes.
+        // Check names and the ready/active tier split are preserved: database + akka-cluster
+        // carry the Ready tag (/health/ready), active-node carries the Active tag (/health/active).
+        // The Akka checks resolve ActorSystem from DI via the transient bridge registered below;
+        // the DatabaseHealthCheck<TContext> resolves a scoped ScadaBridgeDbContext (no factory).
         builder.Services.AddHealthChecks()
-            .AddCheck<DatabaseHealthCheck>("database")
+            .AddTypeActivatedCheck<DatabaseHealthCheck<ScadaBridgeDbContext>>(
-            .AddCheck<AkkaClusterHealthCheck>("akka-cluster")
+                "database",
-            .AddCheck<ActiveNodeHealthCheck>("active-node");
+                failureStatus: null,
+                tags: new[] { ZbHealthTags.Ready })
+            .AddTypeActivatedCheck<AkkaClusterHealthCheck>(
+                "akka-cluster",
+                failureStatus: null,
+                tags: new[] { ZbHealthTags.Ready },
+                args: AkkaClusterStatusPolicy.Default)
+            .AddTypeActivatedCheck<ActiveNodeHealthCheck>(
+                "active-node",
+                failureStatus: null,
+                tags: new[] { ZbHealthTags.Active });
 
         // WP-13: Akka.NET bootstrap via hosted service
         builder.Services.AddSingleton<AkkaHostedService>();
@@ -221,23 +236,17 @@ try
                 && HttpMethods.IsPost(ctx.Request.Method),
             branch => branch.UseAuditWriteMiddleware());
 
-        // WP-12: Map readiness endpoint — returns 503 until ready, 200 when ready.
+        // WP-12: Map the canonical three-tier health endpoints in one call:
-        // REQ-HOST-4a defines readiness as cluster membership + DB connectivity,
+        //   /health/ready  — Ready-tagged checks (database + akka-cluster). REQ-HOST-4a defines
-        // explicitly NOT cluster leadership. The leader-only "active-node" check is
+        //                    readiness as cluster membership + DB connectivity, explicitly NOT
-        // excluded here so a fully operational standby central node reports ready;
+        //                    cluster leadership, so the leader-only active-node check is excluded
-        // leadership is reported separately on /health/active.
+        //                    (a fully operational standby central node still reports ready).
-        app.MapHealthChecks("/health/ready", new HealthCheckOptions
+        //   /health/active — Active-tagged check (active-node); returns 200 only on the cluster
-        {
+        //                    leader; used by Traefik for routing.
-            Predicate = check => check.Name != "active-node",
+        //   /healthz       — bare process liveness; runs no checks (always 200 while the process
-            ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
+        //                    is up). New tier added by adopting the shared library.
-        });
+        // All three are anonymous and use the canonical ZbHealthWriter JSON output.
-
+        app.MapZbHealth();
-        // Active node endpoint — returns 200 only on the cluster leader; used by Traefik for routing
-        app.MapHealthChecks("/health/active", new HealthCheckOptions
-        {
-            Predicate = check => check.Name == "active-node",
-            ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
-        });
 
         app.MapStaticAssets();
         app.MapCentralUI<ZB.MOM.WW.ScadaBridge.Host.Components.App>();

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/HealthCheckTests.cs

@@ -1,11 +1,20 @@
+using System.Linq;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.Extensions.Configuration;
-using ZB.MOM.WW.ScadaBridge.Host.Health;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Options;
+using ZB.MOM.WW.Health;
 
 namespace ZB.MOM.WW.ScadaBridge.Host.Tests;
 
 /// <summary>
-/// WP-12: Tests for /health/ready and /health/active endpoints.
+/// WP-12: Tests for the three-tier health endpoints after adopting the shared
+/// ZB.MOM.WW.Health probes. Verifies that /health/ready, /health/active and the new
+/// /healthz tier are mapped, and that the readiness/active tier split is now carried by
+/// the canonical <see cref="ZbHealthTags"/> (Ready for database + akka-cluster, Active for
+/// active-node) rather than by check-name predicates. These are pure route/tag assertions
+/// — they require no database, LDAP, or formed Akka cluster.
 /// </summary>
 public class HealthCheckTests : IDisposable
 {
@@ -25,41 +34,49 @@ public class HealthCheckTests : IDisposable
         }
     }
 
+    private WebApplicationFactory<Program> CreateCentralFactory()
+    {
+        var factory = new WebApplicationFactory<Program>()
+            .WithWebHostBuilder(builder =>
+            {
+                builder.ConfigureAppConfiguration((context, config) =>
+                {
+                    config.AddInMemoryCollection(new Dictionary<string, string?>
+                    {
+                        ["ScadaBridge:Node:NodeHostname"] = "localhost",
+                        ["ScadaBridge:Node:RemotingPort"] = "0",
+                        ["ScadaBridge:Cluster:SeedNodes:0"] = "akka.tcp://scadabridge@localhost:2551",
+                        ["ScadaBridge:Cluster:SeedNodes:1"] = "akka.tcp://scadabridge@localhost:2552",
+                        ["ScadaBridge:Database:SkipMigrations"] = "true",
+                    });
+                });
+                builder.UseSetting("ScadaBridge:Node:Role", "Central");
+                builder.UseSetting("ScadaBridge:Database:SkipMigrations", "true");
+            });
+        _disposables.Add(factory);
+        return factory;
+    }
+
+    private static IEnumerable<HealthCheckRegistration> Registrations(WebApplicationFactory<Program> factory) =>
+        factory.Services.GetRequiredService<IOptions<HealthCheckServiceOptions>>().Value.Registrations;
+
     [Fact]
-    public async Task HealthReady_Endpoint_ReturnsResponse()
+    public async Task HealthReady_Endpoint_IsMapped()
     {
         var previousEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
         try
         {
             Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Central");
-
+            var factory = CreateCentralFactory();
-            var factory = new WebApplicationFactory<Program>()
-                .WithWebHostBuilder(builder =>
-                {
-                    builder.ConfigureAppConfiguration((context, config) =>
-                    {
-                        config.AddInMemoryCollection(new Dictionary<string, string?>
-                        {
-                            ["ScadaBridge:Node:NodeHostname"] = "localhost",
-                            ["ScadaBridge:Node:RemotingPort"] = "0",
-                            ["ScadaBridge:Cluster:SeedNodes:0"] = "akka.tcp://scadabridge@localhost:2551",
-                            ["ScadaBridge:Cluster:SeedNodes:1"] = "akka.tcp://scadabridge@localhost:2552",
-                            ["ScadaBridge:Database:SkipMigrations"] = "true",
-                        });
-                    });
-                    builder.UseSetting("ScadaBridge:Node:Role", "Central");
-                    builder.UseSetting("ScadaBridge:Database:SkipMigrations", "true");
-                });
-            _disposables.Add(factory);
-
             var client = factory.CreateClient();
             _disposables.Add(client);
 
             var response = await client.GetAsync("/health/ready");
 
-            // The endpoint exists and returns a status code.
+            // The endpoint exists and returns a status code. With test infrastructure
-            // With test infrastructure (no real DB), the database check may fail,
+            // (no real DB / cluster) the readiness checks may report Unhealthy, so we
-            // so we accept either 200 (Healthy) or 503 (Unhealthy).
+            // accept either 200 (Healthy/Degraded) or 503 (Unhealthy) — never 404.
+            Assert.NotEqual(System.Net.HttpStatusCode.NotFound, response.StatusCode);
             Assert.True(
                 response.StatusCode == System.Net.HttpStatusCode.OK ||
                 response.StatusCode == System.Net.HttpStatusCode.ServiceUnavailable,
@@ -72,39 +89,19 @@ public class HealthCheckTests : IDisposable
     }
 
     [Fact]
-    public async Task HealthActive_Endpoint_ReturnsResponse()
+    public async Task HealthActive_Endpoint_IsMapped()
     {
         var previousEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
         try
         {
             Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Central");
-
+            var factory = CreateCentralFactory();
-            var factory = new WebApplicationFactory<Program>()
-                .WithWebHostBuilder(builder =>
-                {
-                    builder.ConfigureAppConfiguration((context, config) =>
-                    {
-                        config.AddInMemoryCollection(new Dictionary<string, string?>
-                        {
-                            ["ScadaBridge:Node:NodeHostname"] = "localhost",
-                            ["ScadaBridge:Node:RemotingPort"] = "0",
-                            ["ScadaBridge:Cluster:SeedNodes:0"] = "akka.tcp://scadabridge@localhost:2551",
-                            ["ScadaBridge:Cluster:SeedNodes:1"] = "akka.tcp://scadabridge@localhost:2552",
-                            ["ScadaBridge:Database:SkipMigrations"] = "true",
-                        });
-                    });
-                    builder.UseSetting("ScadaBridge:Node:Role", "Central");
-                    builder.UseSetting("ScadaBridge:Database:SkipMigrations", "true");
-                });
-            _disposables.Add(factory);
-
             var client = factory.CreateClient();
             _disposables.Add(client);
 
             var response = await client.GetAsync("/health/active");
 
-            // In test mode, the ActorSystem may not be fully available,
+            Assert.NotEqual(System.Net.HttpStatusCode.NotFound, response.StatusCode);
-            // so the active-node check returns 503 (Unhealthy).
             Assert.True(
                 response.StatusCode == System.Net.HttpStatusCode.OK ||
                 response.StatusCode == System.Net.HttpStatusCode.ServiceUnavailable,
@@ -117,46 +114,21 @@ public class HealthCheckTests : IDisposable
     }
 
     [Fact]
-    public async Task HealthReady_Endpoint_ExcludesActiveNodeCheck()
+    public async Task Healthz_LivenessEndpoint_IsMappedAndReturns200()
     {
-        // Host-001 regression: /health/ready must reflect cluster membership + DB
+        // New tier added by adopting the shared library: /healthz runs no checks, so it
-        // connectivity only (REQ-HOST-4a), NOT cluster leadership. The leader-only
+        // returns 200 as long as the process is up — independent of DB / cluster state.
-        // "active-node" check belongs solely to /health/active. If /health/ready
-        // included "active-node", a fully operational standby central node would
-        // permanently report 503, breaking load-balancer failover readiness.
         var previousEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
         try
         {
             Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Central");
-
+            var factory = CreateCentralFactory();
-            var factory = new WebApplicationFactory<Program>()
-                .WithWebHostBuilder(builder =>
-                {
-                    builder.ConfigureAppConfiguration((context, config) =>
-                    {
-                        config.AddInMemoryCollection(new Dictionary<string, string?>
-                        {
-                            ["ScadaBridge:Node:NodeHostname"] = "localhost",
-                            ["ScadaBridge:Node:RemotingPort"] = "0",
-                            ["ScadaBridge:Cluster:SeedNodes:0"] = "akka.tcp://scadabridge@localhost:2551",
-                            ["ScadaBridge:Cluster:SeedNodes:1"] = "akka.tcp://scadabridge@localhost:2552",
-                            ["ScadaBridge:Database:SkipMigrations"] = "true",
-                        });
-                    });
-                    builder.UseSetting("ScadaBridge:Node:Role", "Central");
-                    builder.UseSetting("ScadaBridge:Database:SkipMigrations", "true");
-                });
-            _disposables.Add(factory);
-
             var client = factory.CreateClient();
             _disposables.Add(client);
 
-            var response = await client.GetAsync("/health/ready");
+            var response = await client.GetAsync("/healthz");
-            var body = await response.Content.ReadAsStringAsync();
 
-            // The readiness body lists each executed check by name in its entries map.
+            Assert.Equal(System.Net.HttpStatusCode.OK, response.StatusCode);
-            // The leader-only "active-node" check must not be among them.
-            Assert.DoesNotContain("active-node", body);
         }
         finally
         {
@@ -165,43 +137,54 @@ public class HealthCheckTests : IDisposable
     }
 
     [Fact]
-    public async Task ActiveNodeHealthCheck_SystemNotStarted_ReturnsUnhealthy()
+    public void ReadyTier_Carries_Database_And_AkkaCluster()
     {
-        // AkkaHostedService before StartAsync has ActorSystem == null.
+        // Host-001 regression guard: readiness reflects cluster membership + DB connectivity
-        // The integration test (HealthActive_Endpoint_ReturnsResponse) validates the full
+        // only (REQ-HOST-4a), NOT cluster leadership. The split is now carried by the Ready tag
-        // endpoint wiring. This test validates the null-system path via WebApplicationFactory
+        // rather than a check-name predicate: database + akka-cluster are Ready-tagged, and the
-        // where the ActorSystem may not be available.
+        // leader-only active-node check is NOT — so a fully operational standby central node
+        // still reports ready on /health/ready.
         var previousEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
         try
         {
             Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Central");
-            var factory = new WebApplicationFactory<Program>()
+            var factory = CreateCentralFactory();
-                .WithWebHostBuilder(builder =>
-                {
-                    builder.ConfigureAppConfiguration((context, config) =>
-                    {
-                        config.AddInMemoryCollection(new Dictionary<string, string?>
-                        {
-                            ["ScadaBridge:Node:NodeHostname"] = "localhost",
-                            ["ScadaBridge:Node:RemotingPort"] = "0",
-                            ["ScadaBridge:Cluster:SeedNodes:0"] = "akka.tcp://scadabridge@localhost:2551",
-                            ["ScadaBridge:Database:SkipMigrations"] = "true",
-                        });
-                    });
-                    builder.UseSetting("ScadaBridge:Node:Role", "Central");
-                    builder.UseSetting("ScadaBridge:Database:SkipMigrations", "true");
-                });
-            _disposables.Add(factory);
 
-            var client = factory.CreateClient();
+            var registrations = Registrations(factory).ToDictionary(r => r.Name);
-            _disposables.Add(client);
 
-            var response = await client.GetAsync("/health/active");
+            Assert.True(registrations.ContainsKey("database"), "Expected a 'database' health check.");
-            var body = await response.Content.ReadAsStringAsync();
+            Assert.True(registrations.ContainsKey("akka-cluster"), "Expected an 'akka-cluster' health check.");
 
-            // Active-node check returns 503 when ActorSystem is not yet available or not leader
+            Assert.Contains(ZbHealthTags.Ready, registrations["database"].Tags);
-            Assert.Equal(System.Net.HttpStatusCode.ServiceUnavailable, response.StatusCode);
+            Assert.Contains(ZbHealthTags.Ready, registrations["akka-cluster"].Tags);
-            Assert.Contains("active-node", body);
+
+            // The leader-only active-node check must NOT be on the readiness tier.
+            Assert.DoesNotContain(ZbHealthTags.Ready, registrations["active-node"].Tags);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", previousEnv);
+        }
+    }
+
+    [Fact]
+    public void ActiveTier_Carries_Only_ActiveNode()
+    {
+        // The active-node leader check carries the Active tag (→ /health/active); the readiness
+        // checks do not, so /health/active reports leadership alone.
+        var previousEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
+        try
+        {
+            Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Central");
+            var factory = CreateCentralFactory();
+
+            var registrations = Registrations(factory).ToDictionary(r => r.Name);
+
+            Assert.True(registrations.ContainsKey("active-node"), "Expected an 'active-node' health check.");
+            Assert.Contains(ZbHealthTags.Active, registrations["active-node"].Tags);
+
+            Assert.DoesNotContain(ZbHealthTags.Active, registrations["database"].Tags);
+            Assert.DoesNotContain(ZbHealthTags.Active, registrations["akka-cluster"].Tags);
         }
         finally
         {