fix(host): resolve Host-001 — exclude leader-only active-node check from /health/ready

code-reviews/Host/findings.md

@@ -8,7 +8,7 @@
 | Last reviewed | 2026-05-16 |
 | Reviewer | claude-agent |
 | Commit reviewed | `9c60592` |
-| Open findings | 11 |
+| Open findings | 10 |
 
 ## Summary
 
@@ -54,7 +54,7 @@ no safe workaround.
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.Host/Program.cs:135-145` |
 
 **Description**
@@ -81,7 +81,18 @@ checks and filter by tag). Add a regression test asserting a non-leader node ret
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`). Root cause confirmed against
+`Program.cs`: the `/health/ready` mapping had no `Predicate`, so it executed all
+three registered checks including the leader-only `active-node` check, while
+`ActiveNodeHealthCheck` returns `Unhealthy` on any non-leader node — making a fully
+operational standby central node permanently report `503`. Fix: added
+`Predicate = check => check.Name != "active-node"` to the `/health/ready`
+`HealthCheckOptions`, so readiness now reflects cluster membership + DB connectivity
+only (REQ-HOST-4a); leadership remains reported solely by `/health/active`.
+Regression test `HealthCheckTests.HealthReady_Endpoint_ExcludesActiveNodeCheck`
+asserts the `active-node` check name does not appear in the `/health/ready`
+response body; it failed before the fix and passes after. Full Host suite green
+(156 passed).
 
 ### Host-002 — Akka.Persistence required by REQ-HOST-6 is not configured and not used
 

src/ScadaLink.Host/Program.cs

@@ -131,9 +131,14 @@ try
         app.UseAuthorization();
         app.UseAntiforgery();
 
-        // WP-12: Map readiness endpoint — returns 503 until all checks pass, 200 when ready
+        // WP-12: Map readiness endpoint — returns 503 until ready, 200 when ready.
+        // REQ-HOST-4a defines readiness as cluster membership + DB connectivity,
+        // explicitly NOT cluster leadership. The leader-only "active-node" check is
+        // excluded here so a fully operational standby central node reports ready;
+        // leadership is reported separately on /health/active.
         app.MapHealthChecks("/health/ready", new HealthCheckOptions
         {
+            Predicate = check => check.Name != "active-node",
             ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
         });
 

tests/ScadaLink.Host.Tests/HealthCheckTests.cs

@@ -110,6 +110,54 @@ public class HealthCheckTests : IDisposable
         }
     }
 
+    [Fact]
+    public async Task HealthReady_Endpoint_ExcludesActiveNodeCheck()
+    {
+        // Host-001 regression: /health/ready must reflect cluster membership + DB
+        // connectivity only (REQ-HOST-4a), NOT cluster leadership. The leader-only
+        // "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 = new WebApplicationFactory<Program>()
+                .WithWebHostBuilder(builder =>
+                {
+                    builder.ConfigureAppConfiguration((context, config) =>
+                    {
+                        config.AddInMemoryCollection(new Dictionary<string, string?>
+                        {
+                            ["ScadaLink:Node:NodeHostname"] = "localhost",
+                            ["ScadaLink:Node:RemotingPort"] = "0",
+                            ["ScadaLink:Cluster:SeedNodes:0"] = "akka.tcp://scadalink@localhost:2551",
+                            ["ScadaLink:Cluster:SeedNodes:1"] = "akka.tcp://scadalink@localhost:2552",
+                            ["ScadaLink:Database:SkipMigrations"] = "true",
+                        });
+                    });
+                    builder.UseSetting("ScadaLink:Node:Role", "Central");
+                    builder.UseSetting("ScadaLink:Database:SkipMigrations", "true");
+                });
+            _disposables.Add(factory);
+
+            var client = factory.CreateClient();
+            _disposables.Add(client);
+
+            var response = await client.GetAsync("/health/ready");
+            var body = await response.Content.ReadAsStringAsync();
+
+            // The readiness body lists each executed check by name in its entries map.
+            // The leader-only "active-node" check must not be among them.
+            Assert.DoesNotContain("active-node", body);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", previousEnv);
+        }
+    }
+
     [Fact]
     public async Task ActiveNodeHealthCheck_SystemNotStarted_ReturnsUnhealthy()
     {