fix: adds topology discovery for mongos

lib/core/uri_parser.js

@@ -687,15 +687,6 @@ function parseConnectionString(uri, options, callback) {
     return callback(new MongoParseError('directConnection option requires exactly one host'));
   }
 
-  // NOTE: this behavior will go away in v4.0, we will always auto discover there
-  if (
-    parsedOptions.directConnection == null &&
-    hosts.length === 1 &&
-    parsedOptions.replicaSet == null
-  ) {
-    parsedOptions.directConnection = true;
-  }
-
   const result = {
     hosts: hosts,
     auth: auth.db || auth.username ? auth : null,

test/functional/sharding_connection.test.js

@@ -1,13 +1,29 @@
 'use strict';
 
+const withClient = require('./shared').withClient;
 const setupDatabase = require('./shared').setupDatabase;
 const expect = require('chai').expect;
+const TopologyType = require('../../lib/core/sdam/common').TopologyType;
 
 describe('Sharding (Connection)', function() {
   before(function() {
     return setupDatabase(this.configuration);
   });
 
+  it('Should use sharded topology', {
+    metadata: { requires: { topology: 'sharded' } },
+    test: function() {
+      const client = this.configuration.newClient({}, { useUnifiedTopology: true });
+      return withClient(client, (client, done) => {
+        expect(client).to.exist;
+        expect(client)
+          .nested.property('topology.description.type')
+          .to.equal(TopologyType.Sharded);
+        return done();
+      })();
+    }
+  });
+
   /**
    * @ignore
    */

test/spec/server-discovery-and-monitoring/integration/isMaster-command-error.yml

@@ -27,7 +27,7 @@ tests:
       appname: commandErrorHandshakeTest
     operations:
       # The command error on the initial handshake should mark the server
-      # Unknown and clear the pool.
+      # Unknown (emitting a ServerDescriptionChangedEvent) and clear the pool.
       - name: waitForEvent
         object: testRunner
         arguments:

test/spec/server-discovery-and-monitoring/integration/isMaster-network-error.yml

@@ -26,7 +26,7 @@ tests:
       appname: networkErrorHandshakeTest
     operations:
       # The network error on the initial handshake should mark the server
-      # Unknown and clear the pool.
+      # Unknown (emitting a ServerDescriptionChangedEvent) and clear the pool.
       - name: waitForEvent
         object: testRunner
         arguments:

test/spec/server-discovery-and-monitoring/integration/isMaster-timeout.yml

@@ -27,7 +27,7 @@ tests:
       appname: timeoutMonitorHandshakeTest
     operations:
       # The network error on the initial handshake should mark the server
-      # Unknown and clear the pool.
+      # Unknown (emitting a ServerDescriptionChangedEvent) and clear the pool.
       - name: waitForEvent
         object: testRunner
         arguments:
@@ -101,6 +101,9 @@ tests:
                 failCommands: ["isMaster"]
                 appName: timeoutMonitorCheckTest
                 blockConnection: true
+                # blockTimeMS is evaluated after the waiting for heartbeatFrequencyMS server-side, so this value only
+                # needs to be greater than connectTimeoutMS. The driver will wait for (500+750)ms and the server will
+                # respond after (500+1000)ms.
                 blockTimeMS: 1000
       # The network error on the next check should mark the server Unknown and
       # clear the pool.

test/spec/server-discovery-and-monitoring/monitoring/discovered_standalone.json

@@ -0,0 +1,104 @@
+{
+  "description": "Monitoring a discovered standalone connection",
+  "uri": "mongodb://a:27017/?directConnection=false",
+  "phases": [
+    {
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "minWireVersion": 0,
+            "maxWireVersion": 4
+          }
+        ]
+      ],
+      "outcome": {
+        "events": [
+          {
+            "topology_opening_event": {
+              "topologyId": "42"
+            }
+          },
+          {
+            "topology_description_changed_event": {
+              "topologyId": "42",
+              "previousDescription": {
+                "topologyType": "Unknown",
+                "servers": []
+              },
+              "newDescription": {
+                "topologyType": "Unknown",
+                "servers": [
+                  {
+                    "address": "a:27017",
+                    "arbiters": [],
+                    "hosts": [],
+                    "passives": [],
+                    "type": "Unknown"
+                  }
+                ]
+              }
+            }
+          },
+          {
+            "server_opening_event": {
+              "topologyId": "42",
+              "address": "a:27017"
+            }
+          },
+          {
+            "server_description_changed_event": {
+              "topologyId": "42",
+              "address": "a:27017",
+              "previousDescription": {
+                "address": "a:27017",
+                "arbiters": [],
+                "hosts": [],
+                "passives": [],
+                "type": "Unknown"
+              },
+              "newDescription": {
+                "address": "a:27017",
+                "arbiters": [],
+                "hosts": [],
+                "passives": [],
+                "type": "Standalone"
+              }
+            }
+          },
+          {
+            "topology_description_changed_event": {
+              "topologyId": "42",
+              "previousDescription": {
+                "topologyType": "Unknown",
+                "servers": [
+                  {
+                    "address": "a:27017",
+                    "arbiters": [],
+                    "hosts": [],
+                    "passives": [],
+                    "type": "Unknown"
+                  }
+                ]
+              },
+              "newDescription": {
+                "topologyType": "Single",
+                "servers": [
+                  {
+                    "address": "a:27017",
+                    "arbiters": [],
+                    "hosts": [],
+                    "passives": [],
+                    "type": "Standalone"
+                  }
+                ]
+              }
+            }
+          }
+        ]
+      }
+    }
+  ]
+}

test/spec/server-discovery-and-monitoring/monitoring/discovered_standalone.yml

@@ -0,0 +1,70 @@
+description: "Monitoring a discovered standalone connection"
+uri: "mongodb://a:27017/?directConnection=false"
+phases:
+  -
+    responses:
+      -
+        - "a:27017"
+        - { ok: 1, ismaster: true, minWireVersion: 0, maxWireVersion: 4 }
+
+    outcome:
+      events:
+        -
+          topology_opening_event:
+            topologyId: "42"
+        -
+          topology_description_changed_event:
+            topologyId: "42"
+            previousDescription:
+              topologyType: "Unknown"
+              servers: []
+            newDescription:
+              topologyType: "Unknown"
+              servers:
+                -
+                  address: "a:27017"
+                  arbiters: []
+                  hosts: []
+                  passives: []
+                  type: "Unknown"
+        -
+          server_opening_event:
+            topologyId: "42"
+            address: "a:27017"
+        -
+          server_description_changed_event:
+            topologyId: "42"
+            address: "a:27017"
+            previousDescription:
+              address: "a:27017"
+              arbiters: []
+              hosts: []
+              passives: []
+              type: "Unknown"
+            newDescription:
+              address: "a:27017"
+              arbiters: []
+              hosts: []
+              passives: []
+              type: "Standalone"
+        -
+          topology_description_changed_event:
+            topologyId: "42"
+            previousDescription:
+              topologyType: "Unknown"
+              servers:
+                -
+                  address: "a:27017"
+                  arbiters: []
+                  hosts: []
+                  passives: []
+                  type: "Unknown"
+            newDescription:
+              topologyType: "Single"
+              servers:
+                -
+                  address: "a:27017"
+                  arbiters: []
+                  hosts: []
+                  passives: []
+                  type: "Standalone"

test/spec/server-discovery-and-monitoring/monitoring/standalone.json

@@ -1,6 +1,6 @@
 {
-  "description": "Monitoring a standalone connection",
-  "uri": "mongodb://a:27017",
+  "description": "Monitoring a direct connection",
+  "uri": "mongodb://a:27017/?directConnection=true",
   "phases": [
     {
       "responses": [

test/spec/server-discovery-and-monitoring/monitoring/standalone.yml

@@ -1,5 +1,5 @@
-description: "Monitoring a standalone connection"
-uri: "mongodb://a:27017"
+description: "Monitoring a direct connection"
+uri: "mongodb://a:27017/?directConnection=true"
 phases:
   -
     responses:

test/spec/server-discovery-and-monitoring/monitoring/standalone_suppress_equal_description_changes.json

@@ -1,6 +1,6 @@
 {
-  "description": "Monitoring a standalone connection - suppress update events for equal server descriptions",
-  "uri": "mongodb://a:27017",
+  "description": "Monitoring a direct connection - suppress update events for equal server descriptions",
+  "uri": "mongodb://a:27017/?directConnection=true",
   "phases": [
     {
       "responses": [

test/spec/server-discovery-and-monitoring/monitoring/standalone_suppress_equal_description_changes.yml

@@ -1,5 +1,5 @@
-description: "Monitoring a standalone connection - suppress update events for equal server descriptions"
-uri: "mongodb://a:27017"
+description: "Monitoring a direct connection - suppress update events for equal server descriptions"
+uri: "mongodb://a:27017/?directConnection=true"
 phases:
   -
     responses:

test/spec/server-discovery-and-monitoring/rs/topology_version_greater.json

@@ -157,8 +157,7 @@
             ],
             "setName": "rs",
             "minWireVersion": 0,
-            "maxWireVersion": 9,
-            "topologyVersion": null
+            "maxWireVersion": 9
           }
         ]
       ],

test/spec/server-discovery-and-monitoring/rs/topology_version_greater.yml

@@ -107,8 +107,7 @@ phases: [
                 hosts: ["a:27017", "d:27017"],
                 setName: "rs",
                 minWireVersion: 0,
-                maxWireVersion: 9,
-                topologyVersion: null
+                maxWireVersion: 9
             }]
         ],