Merge pull request #10004 from hillct/master

Fix Event Listeners to comply with (new v3 & v4) MongoDB Driver API changes

Author: vkarpov15

lib/connection.js

@@ -929,7 +929,7 @@ function _setClient(conn, client, options, dbName) {
         }
       });
 
-      db.on('close', function() {
+      client.on('close', function() {
         const type = get(db, 's.topology.s.description.type', '');
         if (type !== 'ReplicaSetWithPrimary') {
           // Implicitly emits 'disconnected'
@@ -945,7 +945,7 @@ function _setClient(conn, client, options, dbName) {
   });
 
   if (!options.useUnifiedTopology) {
-    db.on('reconnect', function() {
+    client.on('reconnect', function() {
       _handleReconnect();
     });
 
@@ -965,7 +965,7 @@ function _setClient(conn, client, options, dbName) {
     });
   }
   if (!options.useUnifiedTopology) {
-    db.on('close', function() {
+    client.on('close', function() {
       // Implicitly emits 'disconnected'
       conn.readyState = STATES.disconnected;
     });
@@ -984,7 +984,7 @@ function _setClient(conn, client, options, dbName) {
       }
     });
 
-    db.on('timeout', function() {
+    client.on('timeout', function() {
       conn.emit('timeout');
     });
   }