From 1dab5e0bbd9cbffa71b6cd800551ba89e3a7f29e Mon Sep 17 00:00:00 2001
From: Karen Chen <karen.chen@improving.com>
Date: Tue, 11 Mar 2025 10:20:24 -0700
Subject: [PATCH] fix: verify connection is not a stale writer in the monitor

---
 .../monitoring/ClusterTopologyMonitorImpl.java       | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/wrapper/src/main/java/software/amazon/jdbc/hostlistprovider/monitoring/ClusterTopologyMonitorImpl.java b/wrapper/src/main/java/software/amazon/jdbc/hostlistprovider/monitoring/ClusterTopologyMonitorImpl.java
index 80a586249..055e6c38d 100644
--- a/wrapper/src/main/java/software/amazon/jdbc/hostlistprovider/monitoring/ClusterTopologyMonitorImpl.java
+++ b/wrapper/src/main/java/software/amazon/jdbc/hostlistprovider/monitoring/ClusterTopologyMonitorImpl.java
@@ -818,6 +818,18 @@ public void run() {
               connection = null;
             }
 
+            if (!StringUtils.isNullOrEmpty(writerId)) {
+              try {
+                if (this.monitor.pluginService.getHostRole(connection) != HostRole.WRITER) {
+                  // The first connection after failover may be stale.
+                  writerId = null;
+                }
+              } catch (SQLException e) {
+                // Invalid connection, retry.
+                continue;
+              }
+            }
+
             if (!StringUtils.isNullOrEmpty(writerId)) {
               // this prevents closing connection in finally block
               if (!this.monitor.nodeThreadsWriterConnection.compareAndSet(null, connection)) {