From 27cefad180684ed668ab1096a95db1bc0b4cc30b Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Wed, 16 Oct 2019 13:51:26 -0400
Subject: [PATCH] fix(connection): ensure repeated `close` events from
 useUnifiedTopology don't disconnect Mongoose from replica set

Fix #8224
Re: NODE-2251
---
 lib/connection.js | 44 ++++++++++++++++++++++++++++----------------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/lib/connection.js b/lib/connection.js
index 43e4028510b..d3fde9d4c15 100644
--- a/lib/connection.js
+++ b/lib/connection.js
@@ -639,18 +639,28 @@ Connection.prototype.openUri = function(uri, options, callback) {
       _this.db = db;
 
       // `useUnifiedTopology` events
-      if (options.useUnifiedTopology &&
-          get(db, 's.topology.s.description.type') === 'Single') {
-        const server = Array.from(db.s.topology.s.servers.values())[0];
-        server.s.pool.on('reconnect', () => {
-          _handleReconnect();
-        });
-        server.s.pool.on('reconnectFailed', () => {
-          _this.emit('reconnectFailed');
-        });
-        server.s.pool.on('timeout', () => {
-          _this.emit('timeout');
-        });
+      const type = get(db, 's.topology.s.description.type', '');
+      if (options.useUnifiedTopology) {
+        if (type === 'Single') {
+          const server = Array.from(db.s.topology.s.servers.values())[0];
+          server.s.pool.on('reconnect', () => {
+            _handleReconnect();
+          });
+          server.s.pool.on('reconnectFailed', () => {
+            _this.emit('reconnectFailed');
+          });
+          server.s.pool.on('timeout', () => {
+            _this.emit('timeout');
+          });
+        } else if (type.startsWith('ReplicaSet')) {
+          db.on('close', function() {
+            const type = get(db, 's.topology.s.description.type', '');
+            if (type !== 'ReplicaSetWithPrimary') {
+              // Implicitly emits 'disconnected'
+              _this.readyState = STATES.disconnected;
+            }
+          });
+        }
       }
 
       // Backwards compat for mongoose 4.x
@@ -674,10 +684,12 @@ Connection.prototype.openUri = function(uri, options, callback) {
           _this.emit('attemptReconnect');
         });
       }
-      db.on('close', function() {
-        // Implicitly emits 'disconnected'
-        _this.readyState = STATES.disconnected;
-      });
+      if (!options.useUnifiedTopology || !type.startsWith('ReplicaSet')) {
+        db.on('close', function() {
+          // Implicitly emits 'disconnected'
+          _this.readyState = STATES.disconnected;
+        });
+      }
       client.on('left', function() {
         if (_this.readyState === STATES.connected &&
             get(db, 's.topology.s.coreTopology.s.replicaSetState.topologyType') === 'ReplicaSetNoPrimary') {