From 5303656a694f137a66a5ad60681b48a33f54d837 Mon Sep 17 00:00:00 2001
From: Naoya Yoshizawa <azihsoyn@gmail.com>
Date: Thu, 5 Mar 2026 15:28:31 +0900
Subject: [PATCH] fix(pg): prevent process crash during Aurora failover

Two issues cause Node.js process to crash when an Aurora failover occurs:

1. AwsPgInternalPoolClient creates a pg.Pool without an 'error' event
   handler. During failover, idle connections are terminated by the
   server, emitting 'error' events on the pool. Without a handler,
   Node.js throws an uncaught exception and the process exits.

2. AwsPGPooledConnection.release() unconditionally calls
   this.targetClient.client.release(), but after failover the new
   client may not have a release() method (e.g., a direct connection
   rather than a pooled connection), causing a TypeError.

Fix 1: Attach a no-op 'error' handler to the internal pg.Pool so idle
connection errors are swallowed. The failover plugin handles
reconnection.

Fix 2: Check if release() exists on the underlying client before
calling it.
---
 pg/lib/client.ts                      | 6 +++++-
 pg/lib/icp/pg_internal_pool_client.ts | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/pg/lib/client.ts b/pg/lib/client.ts
index 4517e1659..264143b18 100644
--- a/pg/lib/client.ts
+++ b/pg/lib/client.ts
@@ -358,7 +358,11 @@ class AwsPGPooledConnection extends BaseAwsPgClient {
           throw new UndefinedClientError();
         }
         this.pluginService.removeErrorListener(this.targetClient);
-        return await this.targetClient.client.release();
+        // After failover, the new target client may not have a release() method
+        // (e.g., a direct connection instead of a pooled connection).
+        if (typeof this.targetClient.client?.release === "function") {
+          return await this.targetClient.client.release();
+        }
       },
       null
     );
diff --git a/pg/lib/icp/pg_internal_pool_client.ts b/pg/lib/icp/pg_internal_pool_client.ts
index ed0324db1..e7d6c6128 100644
--- a/pg/lib/icp/pg_internal_pool_client.ts
+++ b/pg/lib/icp/pg_internal_pool_client.ts
@@ -25,6 +25,12 @@ export class AwsPgInternalPoolClient implements AwsInternalPoolClient {
 
   constructor(props: pkgPg.PoolConfig) {
     this.targetPool = new pkgPg.Pool(props);
+    // Handle idle client errors to prevent process crash during Aurora failover.
+    // When a failover occurs, idle connections in the pool are terminated by the server,
+    // which emits 'error' events. Without this handler, Node.js throws an uncaught exception.
+    this.targetPool.on("error", () => {
+      // Intentionally swallowed. The failover plugin will handle reconnection.
+    });
   }
 
   async end(): Promise<any> {