fix: avoid heartbeat check on LoadBalanced topologies, dont treat connection as heartbeat to avoid other cases where there is no heartbeat

Author: vkarpov15

lib/connection.js

@@ -106,6 +106,18 @@ Object.setPrototypeOf(Connection.prototype, EventEmitter.prototype);
 
 Object.defineProperty(Connection.prototype, 'readyState', {
   get: function() {
+    // If connection thinks it is connected, but we haven't received a heartbeat in 2 heartbeat intervals,
+    // that likely means the connection is stale (potentially due to frozen AWS Lambda container)
+    if (
+      this._readyState === STATES.connected &&
+      this._lastHeartbeatAt != null &&
+      // LoadBalanced topology (behind haproxy, including Atlas serverless instances) don't use heartbeats,
+      // so we can't use this check in that case.
+      this.client?.topology?.s?.description?.type !== 'LoadBalanced' &&
+      typeof this.client?.topology?.s?.description?.heartbeatFrequencyMS === 'number' &&
+      Date.now() - this._lastHeartbeatAt >= this.client.topology.s.description.heartbeatFrequencyMS * 2) {
+      return STATES.disconnected;
+    }
     return this._readyState;
   },
   set: function(val) {

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

@@ -426,9 +426,6 @@ function _setClient(conn, client, options, dbName) {
   }
 
   conn.onOpen();
-  if (client.topology?.s?.state === 'connected') {
-    conn._lastHeartbeatAt = Date.now();
-  }
 
   for (const i in conn.collections) {
     if (utils.object.hasOwnProperty(conn.collections, i)) {