From e1ee37e508b7a1a845212edfd9b175e67ed61e9e Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Tue, 16 Jun 2026 07:02:26 -0400
Subject: [PATCH] fix(siteeventlog): gate EventLogPurge to active node via
 IClusterNodeProvider.SelfIsPrimary (#29, M2.15)

---
 .../SiteServiceRegistration.cs                      | 13 +++++++++++++
 .../CompositionRootTests.cs                         |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/src/ZB.MOM.WW.ScadaBridge.Host/SiteServiceRegistration.cs b/src/ZB.MOM.WW.ScadaBridge.Host/SiteServiceRegistration.cs
index 70cfec10..367a55ca 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Host/SiteServiceRegistration.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Host/SiteServiceRegistration.cs
@@ -96,6 +96,19 @@ public static class SiteServiceRegistration
             return new AkkaClusterNodeProvider(akkaService, siteRole);
         });
 
+        // SiteEventLogging-019 / #29 (M2.15): the EventLogPurgeService runs on every
+        // site host node but consults this optional gate each tick and early-exits on
+        // the standby. Register it to delegate to IClusterNodeProvider.SelfIsPrimary
+        // (the canonical "this node is Up AND cluster leader" check) so purge runs ONLY
+        // on the active node — no duplicated cluster logic. Non-clustered test hosts that
+        // never call SiteServiceRegistration leave it unregistered, so the purge defaults
+        // to always-run (the pre-fix behaviour, preserved).
+        services.AddSingleton<SiteEventLogActiveNodeCheck>(sp =>
+        {
+            var nodeProvider = sp.GetRequiredService<IClusterNodeProvider>();
+            return () => nodeProvider.SelfIsPrimary;
+        });
+
         // Options binding
         BindSharedOptions(services, config);
         services.Configure<SiteRuntimeOptions>(config.GetSection("ScadaBridge:SiteRuntime"));
diff --git a/tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CompositionRootTests.cs b/tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CompositionRootTests.cs
index 15750328..ba94e831 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CompositionRootTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CompositionRootTests.cs
@@ -405,6 +405,9 @@ public class SiteCompositionRootTests : IDisposable
         new object[] { typeof(IEventLogQueryService) },
         new object[] { typeof(ISiteIdentityProvider) },
         new object[] { typeof(IHealthReportTransport) },
+        // M2.15 (#29): the active-node purge gate must be registered on site nodes
+        // so EventLogPurge only runs on the active node.
+        new object[] { typeof(SiteEventLogActiveNodeCheck) },
     };
 
     // --- Scoped services ---