fix(connection): propagate changes to _lastHeartbeatAt to useDb() child connections

Fix #15635

Author: vkarpov15

lib/drivers/node-mongodb-native/connection.js

@@ -118,7 +118,7 @@ NativeConnection.prototype.useDb = function(name, options) {
 
   newConn.name = name;
 
-  // push onto the otherDbs stack, this is used when state changes
+  // push onto the otherDbs stack, this is used when state changes and when heartbeat is received
   if (options.noListener !== true) {
     this.otherDbs.push(newConn);
   }
@@ -501,6 +501,9 @@ function _setClient(conn, client, options, dbName) {
 
   client.on('serverHeartbeatSucceeded', () => {
     conn._lastHeartbeatAt = Date.now();
+    for (const otherDb of conn.otherDbs) {
+      otherDb._lastHeartbeatAt = conn._lastHeartbeatAt;
+    }
   });
 
   if (options.monitorCommands) {

test/connection.test.js

@@ -870,6 +870,22 @@ describe('connections:', function() {
 
       await db.close();
     });
+
+    it('updates child dbs lastHeartbeatAt (gh-15635)', async function () {
+      const db = await mongoose.createConnection(start.uri).asPromise();
+
+      const schema = mongoose.Schema({ name: String }, { autoCreate: false, autoIndex: false });
+      const Test = db.model('Test', schema);
+      await Test.deleteMany({});
+      await Test.create({ name: 'gh-11821' });
+
+      const db2 = db.useDb(start.databases[1]);
+
+      const now = Date.now();
+      db.client.emit('serverHeartbeatSucceeded');
+      assert.ok(db._lastHeartbeatAt >= now);
+      assert.ok(db2._lastHeartbeatAt >= now);
+    });
   });
 
   describe('shouldAuthenticate()', function() {