feat: directConnection adds unify behavior for replica set discovery

lib/connection_string.js

@@ -37,6 +37,10 @@ function matchesParentDomain(srvAddress, parentDomain) {
 function parseSrvConnectionString(uri, options, callback) {
   const result = URL.parse(uri, true);
 
+  if (options.directConnection || options.directconnection) {
+    return callback(new MongoParseError('directConnection not supported with SRV URI'));
+  }
+
   if (result.hostname.split('.').length < 3) {
     return callback(new MongoParseError('URI does not have hostname, domain name and tld'));
   }
@@ -217,7 +221,8 @@ const CASE_TRANSLATION = {
   tlscertificatekeyfile: 'tlsCertificateKeyFile',
   tlscertificatekeyfilepassword: 'tlsCertificateKeyFilePassword',
   wtimeout: 'wTimeoutMS',
-  j: 'journal'
+  j: 'journal',
+  directconnection: 'directConnection'
 };
 
 /**
@@ -594,10 +599,6 @@ function parseConnectionString(uri, options, callback) {
     return callback(new MongoParseError('Invalid protocol provided'));
   }
 
-  if (protocol === PROTOCOL_MONGODB_SRV) {
-    return parseSrvConnectionString(uri, options, callback);
-  }
-
   const dbAndQuery = cap[4].split('?');
   const db = dbAndQuery.length > 0 ? dbAndQuery[0] : null;
   const query = dbAndQuery.length > 1 ? dbAndQuery[1] : null;
@@ -613,6 +614,12 @@ function parseConnectionString(uri, options, callback) {
     return callback(parseError);
   }
 
+  parsedOptions = Object.assign({}, parsedOptions, options);
+
+  if (protocol === PROTOCOL_MONGODB_SRV) {
+    return parseSrvConnectionString(uri, parsedOptions, callback);
+  }
+
   const auth = { username: null, password: null, db: db && db !== '' ? qs.unescape(db) : null };
   if (parsedOptions.auth) {
     // maintain support for legacy options passed into `MongoClient`
@@ -706,6 +713,22 @@ function parseConnectionString(uri, options, callback) {
     return callback(new MongoParseError('No hostname or hostnames provided in connection string'));
   }
 
+  const directConnection = !!parsedOptions.directConnection;
+  if (directConnection && hosts.length !== 1) {
+    // If the option is set to true, the driver MUST validate that there is exactly one host given
+    // in the host list in the URI, and fail client creation otherwise.
+    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,

lib/mongo_client.js

@@ -143,6 +143,7 @@ const { connect, validOptions } = require('./operations/connect');
  * @param {boolean} [options.useNewUrlParser=true] Determines whether or not to use the new url parser. Enables the new, spec-compliant, url parser shipped in the core driver. This url parser fixes a number of problems with the original parser, and aims to outright replace that parser in the near future. Defaults to true, and must be explicitly set to false to use the legacy url parser.
  * @param {DriverInfoOptions} [options.driverInfo] Allows a wrapping driver to amend the client metadata generated by the driver to include information about the wrapping driver
  * @param {AutoEncrypter~AutoEncryptionOptions} [options.autoEncryption] Optionally enable client side auto encryption
+ * @param {boolean} [options.directConnection=false] Enable directConnection
  * @returns {MongoClient} a MongoClient instance
  */
 function MongoClient(url, options) {
@@ -388,6 +389,7 @@ MongoClient.prototype.isConnected = function(options) {
  * @param {number} [options.numberOfRetries=5] The number of retries for a tailable cursor
  * @param {boolean} [options.auto_reconnect=true] Enable auto reconnecting for single server instances
  * @param {number} [options.minSize] If present, the connection pool will be initialized with minSize connections, and will never dip below minSize connections
+ * @param {boolean} [options.directConnection=false] Enable directConnection
  * @param {MongoClient~connectCallback} [callback] The command result callback
  * @returns {Promise<MongoClient>} returns Promise if no callback passed
  */

lib/operations/connect.js

@@ -111,7 +111,8 @@ const validOptionNames = [
   'tlsCertificateKeyFilePassword',
   'minHeartbeatFrequencyMS',
   'heartbeatFrequencyMS',
-  'waitQueueTimeoutMS'
+  'waitQueueTimeoutMS',
+  'directConnection'
 ];
 
 const ignoreOptionNames = ['native_parser'];

lib/sdam/topology.js

@@ -798,10 +798,16 @@ function parseStringSeedlist(seedlist) {
 }
 
 function topologyTypeFromSeedlist(seedlist, options) {
+  if (options.directConnection) {
+    return TopologyType.Single;
+  }
+
   const replicaSet = options.replicaSet || options.setName || options.rs_name;
-  if (seedlist.length === 1 && !replicaSet) return TopologyType.Single;
-  if (replicaSet) return TopologyType.ReplicaSetNoPrimary;
-  return TopologyType.Unknown;
+  if (replicaSet == null) {
+    return TopologyType.Unknown;
+  }
+
+  return TopologyType.ReplicaSetNoPrimary;
 }
 
 function randomSelection(array) {

lib/sdam/topology_description.js

@@ -163,7 +163,7 @@ class TopologyDescription {
     }
 
     if (topologyType === TopologyType.Unknown) {
-      if (serverType === ServerType.Standalone) {
+      if (serverType === ServerType.Standalone && this.servers.size !== 1) {
         serverDescriptions.delete(address);
       } else {
         topologyType = topologyTypeForServerType(serverType);
@@ -277,8 +277,22 @@ class TopologyDescription {
 }
 
 function topologyTypeForServerType(serverType) {
-  if (serverType === ServerType.Mongos) return TopologyType.Sharded;
-  if (serverType === ServerType.RSPrimary) return TopologyType.ReplicaSetWithPrimary;
+  if (serverType === ServerType.Standalone) {
+    return TopologyType.Single;
+  }
+
+  if (serverType === ServerType.Mongos) {
+    return TopologyType.Sharded;
+  }
+
+  if (serverType === ServerType.RSPrimary) {
+    return TopologyType.ReplicaSetWithPrimary;
+  }
+
+  if (serverType === ServerType.RSGhost || serverType === ServerType.Unknown) {
+    return TopologyType.Unknown;
+  }
+
   return TopologyType.ReplicaSetNoPrimary;
 }
 

test/spec/initial-dns-seedlist-discovery/direct-connection-false.json

@@ -0,0 +1,14 @@
+{
+  "uri": "mongodb+srv://test3.test.build.10gen.cc/?directConnection=false",
+  "seeds": [
+    "localhost.test.build.10gen.cc:27017"
+  ],
+  "hosts": [
+    "localhost:27017",
+    "localhost:27018",
+    "localhost:27019"
+  ],
+  "options": {
+    "ssl": true
+  }
+}

test/spec/initial-dns-seedlist-discovery/direct-connection-false.yml

@@ -0,0 +1,9 @@
+uri: "mongodb+srv://test3.test.build.10gen.cc/?directConnection=false"
+seeds:
+    - localhost.test.build.10gen.cc:27017
+hosts:
+    - localhost:27017
+    - localhost:27018
+    - localhost:27019
+options:
+    ssl: true

test/spec/initial-dns-seedlist-discovery/direct-connection-true.json

@@ -0,0 +1,7 @@
+{
+  "uri": "mongodb+srv://test3.test.build.10gen.cc/?directConnection=true",
+  "seeds": [],
+  "hosts": [],
+  "error": true,
+  "comment": "Should fail because directConnection=true is incompatible with SRV URIs."
+}

test/spec/initial-dns-seedlist-discovery/direct-connection-true.yml

@@ -0,0 +1,5 @@
+uri: "mongodb+srv://test3.test.build.10gen.cc/?directConnection=true"
+seeds: []
+hosts: []
+error: true
+comment: Should fail because directConnection=true is incompatible with SRV URIs.

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

@@ -1,5 +1,7 @@
 description: "Replica set member with large maxWireVersion"
+
 uri: "mongodb://a,b/?replicaSet=rs"
+
 phases: [
     {
         responses: [

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

@@ -1,5 +1,7 @@
 description: "Replica set member and an unknown server"
+
 uri: "mongodb://a,b/?replicaSet=rs"
+
 phases: [
     {
         responses: [

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

@@ -1,6 +1,6 @@
 {
-  "description": "Discover arbiters",
-  "uri": "mongodb://a/?replicaSet=rs",
+  "description": "Discover arbiters with directConnection URI option",
+  "uri": "mongodb://a/?directConnection=false",
   "phases": [
     {
       "responses": [

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

@@ -1,6 +1,6 @@
-description: "Discover arbiters"
+description: "Discover arbiters with directConnection URI option"
 
-uri: "mongodb://a/?replicaSet=rs"
+uri: "mongodb://a/?directConnection=false"
 
 phases: [
 

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

@@ -0,0 +1,41 @@
+{
+  "description": "Discover arbiters with replicaSet URI option",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "arbiters": [
+              "b:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 6
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs"
+          },
+          "b:27017": {
+            "type": "Unknown",
+            "setName": null
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}

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

@@ -0,0 +1,43 @@
+description: "Discover arbiters with replicaSet URI option"
+
+uri: "mongodb://a/?replicaSet=rs"
+
+phases: [
+
+    {
+        responses: [
+
+                ["a:27017", {
+
+                    ok: 1,
+                    ismaster: true,
+                    hosts: ["a:27017"],
+                    arbiters: ["b:27017"],
+                    setName: "rs",
+                    minWireVersion: 0,
+                    maxWireVersion: 6
+                }]
+        ],
+
+        outcome: {
+
+            servers: {
+
+                "a:27017": {
+
+                    type: "RSPrimary",
+                    setName: "rs"
+                },
+
+                "b:27017": {
+
+                    type: "Unknown",
+                    setName:
+                }
+            },
+            topologyType: "ReplicaSetWithPrimary",
+            logicalSessionTimeoutMinutes: null,
+            setName: "rs"
+        }
+    }
+]

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

@@ -0,0 +1,31 @@
+{
+  "description": "Discover ghost with directConnection URI option",
+  "uri": "mongodb://b/?directConnection=false",
+  "phases": [
+    {
+      "responses": [
+        [
+          "b:27017",
+          {
+            "ok": 1,
+            "ismaster": false,
+            "isreplicaset": true,
+            "minWireVersion": 0,
+            "maxWireVersion": 6
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "b:27017": {
+            "type": "RSGhost",
+            "setName": null
+          }
+        },
+        "topologyType": "Unknown",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": null
+      }
+    }
+  ]
+}

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

@@ -0,0 +1,35 @@
+description: "Discover ghost with directConnection URI option"
+
+uri: "mongodb://b/?directConnection=false"
+
+phases: [
+
+    {
+        responses: [
+
+                ["b:27017", {
+
+                    ok: 1,
+                    ismaster: false,
+                    isreplicaset: true,
+                    minWireVersion: 0,
+                    maxWireVersion: 6
+                }]
+        ],
+
+        outcome: {
+
+            servers: {
+
+                "b:27017": {
+
+                    type: "RSGhost",
+                    setName:
+                }
+            },
+            topologyType: "Unknown",
+            logicalSessionTimeoutMinutes: null,
+            setName:
+        }
+    }
+]

test/spec/server-discovery-and-monitoring/rs/ghost_discovered.json → test/spec/server-discovery-and-monitoring/rs/discover_ghost_replicaset.json

@@ -1,5 +1,5 @@
 {
-  "description": "Ghost discovered",
+  "description": "Discover ghost with replicaSet URI option",
   "uri": "mongodb://a,b/?replicaSet=rs",
   "phases": [
     {

test/spec/server-discovery-and-monitoring/rs/ghost_discovered.yml → test/spec/server-discovery-and-monitoring/rs/discover_ghost_replicaset.yml

@@ -1,4 +1,4 @@
-description: "Ghost discovered"
+description: "Discover ghost with replicaSet URI option"
 
 uri: "mongodb://a,b/?replicaSet=rs"