From 1147ebff9fd6d978e72408b6b50510b323f8418f Mon Sep 17 00:00:00 2001
From: Matt Broadstone <mbroadst@mongodb.com>
Date: Thu, 24 Oct 2019 20:02:10 -0400
Subject: [PATCH] fix(sdam): don't remove unknown servers in topology updates

NODE-2214
---
 lib/core/sdam/topology_description.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/core/sdam/topology_description.js b/lib/core/sdam/topology_description.js
index 7fef2bc643..c2a1bd6191 100644
--- a/lib/core/sdam/topology_description.js
+++ b/lib/core/sdam/topology_description.js
@@ -191,7 +191,7 @@ class TopologyDescription {
     }
 
     if (topologyType === TopologyType.ReplicaSetNoPrimary) {
-      if ([ServerType.Mongos, ServerType.Unknown].indexOf(serverType) >= 0) {
+      if ([ServerType.Standalone, ServerType.Mongos].indexOf(serverType) >= 0) {
         serverDescriptions.delete(address);
       }