From 1ac273cc48a1c93120a20356c654e7d1cf2631a4 Mon Sep 17 00:00:00 2001
From: Jorge Duarte Rodriguez <jduarte@roadstr.io>
Date: Sat, 5 Oct 2019 04:58:34 +0200
Subject: [PATCH 1/3] NODE-2147: Proper server topology management.

---
 lib/sdam/server.js       | 10 ++++++----
 lib/sdam/topology.js     |  8 +++++++-
 lib/topologies/server.js |  2 +-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/lib/sdam/server.js b/lib/sdam/server.js
index bb0d1bb3f..5a33d7cf8 100644
--- a/lib/sdam/server.js
+++ b/lib/sdam/server.js
@@ -126,10 +126,12 @@ class Server extends EventEmitter {
     this.s.pool.on('error', errorEventHandler(this));
     this.s.pool.on('parseError', parseErrorEventHandler(this));
 
-    // it is unclear whether consumers should even know about these events
-    // this.s.pool.on('timeout', timeoutEventHandler(this));
-    // this.s.pool.on('reconnect', reconnectEventHandler(this));
-    // this.s.pool.on('reconnectFailed', errorEventHandler(this));
+    // relay events to ensure consistent topology reconnection/connection status consistency.
+    // for more details, check: NODE-2147: Unexpected behaviours using useUnifiedTopology: true
+ 
+    this.s.pool.on('timeout', timeoutEventHandler(this));
+    this.s.pool.on('reconnect', reconnectEventHandler(this));
+    this.s.pool.on('reconnectFailed', errorEventHandler(this));
 
     // relay all command monitoring events
     relayEvents(this.s.pool, this, ['commandStarted', 'commandSucceeded', 'commandFailed']);
diff --git a/lib/sdam/topology.js b/lib/sdam/topology.js
index 5083b61ba..46dda2e09 100644
--- a/lib/sdam/topology.js
+++ b/lib/sdam/topology.js
@@ -54,7 +54,8 @@ const LOCAL_SERVER_EVENTS = SERVER_RELAY_EVENTS.concat([
   'connect',
   'descriptionReceived',
   'close',
-  'ended'
+  'ended',
+  'reconnectFailed'
 ]);
 
 /**
@@ -843,6 +844,11 @@ function updateServers(topology, incomingServerDescription) {
 
 function serverConnectEventHandler(server, topology) {
   return function(/* isMaster, err */) {
+    // close topology on reconnectFailed.
+    server.s.pool.on('reconnectFailed', () => {
+      topology.close();
+    });
+    
     server.monitor({
       initial: true,
       heartbeatFrequencyMS: topology.description.heartbeatFrequencyMS
diff --git a/lib/topologies/server.js b/lib/topologies/server.js
index 2144e750f..5606880e3 100644
--- a/lib/topologies/server.js
+++ b/lib/topologies/server.js
@@ -382,7 +382,7 @@ var eventHandler = function(self, event) {
       event === 'timeout' ||
       event === 'reconnect' ||
       event === 'attemptReconnect' ||
-      'reconnectFailed'
+      event === 'reconnectFailed'
     ) {
       // Remove server instance from accounting
       if (

From 3077b2eba6c1f345247d70d7c7d7022ae4112ca1 Mon Sep 17 00:00:00 2001
From: Jorge Duarte Rodriguez <jduarte@roadstr.io>
Date: Mon, 7 Oct 2019 02:15:14 +0200
Subject: [PATCH 2/3] Add missing functions and fix indenting.

---
 lib/sdam/server.js   | 18 ++++++++++++++++--
 lib/sdam/topology.js |  2 +-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/lib/sdam/server.js b/lib/sdam/server.js
index 5a33d7cf8..29ce5b877 100644
--- a/lib/sdam/server.js
+++ b/lib/sdam/server.js
@@ -126,9 +126,8 @@ class Server extends EventEmitter {
     this.s.pool.on('error', errorEventHandler(this));
     this.s.pool.on('parseError', parseErrorEventHandler(this));
 
-    // relay events to ensure consistent topology reconnection/connection status consistency.
+    // relay events to ensure topology reconnection/connection status consistency.
     // for more details, check: NODE-2147: Unexpected behaviours using useUnifiedTopology: true
- 
     this.s.pool.on('timeout', timeoutEventHandler(this));
     this.s.pool.on('reconnect', reconnectEventHandler(this));
     this.s.pool.on('reconnectFailed', errorEventHandler(this));
@@ -391,4 +390,19 @@ function parseErrorEventHandler(server) {
   };
 }
 
+function timeoutEventHandler(server) {
+  return function() {
+    server.s.state = STATE_DISCONNECTED;
+    server.emit('error', new MongoNetworkError('Pool timeout event triggered.'));
+    server.emit('close');
+  };    
+}
+
+function reconnectEventHandler(server) {
+  return function() {
+    server.s.state = STATE_CONNECTING;
+    server.emit('reconnect');
+  };
+} 
+
 module.exports = Server;
diff --git a/lib/sdam/topology.js b/lib/sdam/topology.js
index 46dda2e09..eeaeb08ad 100644
--- a/lib/sdam/topology.js
+++ b/lib/sdam/topology.js
@@ -848,7 +848,7 @@ function serverConnectEventHandler(server, topology) {
     server.s.pool.on('reconnectFailed', () => {
       topology.close();
     });
-    
+
     server.monitor({
       initial: true,
       heartbeatFrequencyMS: topology.description.heartbeatFrequencyMS

From dd0ccd544756a389417f19ab3dd65fd9d97dc50c Mon Sep 17 00:00:00 2001
From: Jorge Duarte Rodriguez <jduarte@roadstr.io>
Date: Mon, 7 Oct 2019 02:31:15 +0200
Subject: [PATCH 3/3] Fix linting.

---
 lib/sdam/server.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/sdam/server.js b/lib/sdam/server.js
index 29ce5b877..d82808f02 100644
--- a/lib/sdam/server.js
+++ b/lib/sdam/server.js
@@ -395,7 +395,7 @@ function timeoutEventHandler(server) {
     server.s.state = STATE_DISCONNECTED;
     server.emit('error', new MongoNetworkError('Pool timeout event triggered.'));
     server.emit('close');
-  };    
+  };
 }
 
 function reconnectEventHandler(server) {
@@ -403,6 +403,6 @@ function reconnectEventHandler(server) {
     server.s.state = STATE_CONNECTING;
     server.emit('reconnect');
   };
-} 
+}
 
 module.exports = Server;