refactor: don't authenticate monitoring connections

Author: mbroadst

lib/core/sdam/monitor.js

@@ -61,27 +61,29 @@ class Monitor extends EventEmitter {
 
     // TODO: refactor this to pull it directly from the pool, requires new ConnectionPool integration
     const addressParts = server.description.address.split(':');
-    this.connectOptions = Object.freeze(
-      Object.assign(
-        {
-          id: '<monitor>',
-          host: addressParts[0],
-          port: parseInt(addressParts[1], 10),
-          bson: server.s.bson,
-          connectionType: Connection
-        },
-        server.s.options,
-        this.options,
-
-        // force BSON serialization options
-        {
-          raw: false,
-          promoteLongs: true,
-          promoteValues: true,
-          promoteBuffers: true
-        }
-      )
+    const connectOptions = Object.assign(
+      {
+        id: '<monitor>',
+        host: addressParts[0],
+        port: parseInt(addressParts[1], 10),
+        bson: server.s.bson,
+        connectionType: Connection
+      },
+      server.s.options,
+      this.options,
+
+      // force BSON serialization options
+      {
+        raw: false,
+        promoteLongs: true,
+        promoteValues: true,
+        promoteBuffers: true
+      }
     );
+
+    // ensure no authentication is used for monitoring
+    delete connectOptions.credentials;
+    this.connectOptions = Object.freeze(connectOptions);
   }
 
   connect() {

lib/core/sdam/topology.js

@@ -276,7 +276,7 @@ class Topology extends EventEmitter {
 
     translateReadPreference(options);
     const readPreference = options.readPreference || ReadPreference.primary;
-    this.selectServer(readPreferenceServerSelector(readPreference), options, err => {
+    const connectHandler = err => {
       if (err) {
         this.close();
 
@@ -294,7 +294,15 @@ class Topology extends EventEmitter {
       this.emit('connect', this);
 
       if (typeof callback === 'function') callback(err, this);
-    });
+    };
+
+    // TODO: NODE-2471
+    if (this.s.credentials) {
+      this.command('admin.$cmd', { ping: 1 }, { readPreference }, connectHandler);
+      return;
+    }
+
+    this.selectServer(readPreferenceServerSelector(readPreference), options, connectHandler);
   }
 
   /**