SERVER-50508 Rename ConnectionType::MASTER to ConnectionType::kStandalone

35 files changed, 223 insertions, 178 deletions

diff --git a/src/mongo/client/connection_string.cpp b/src/mongo/client/connection_string.cpp
index f3dd2fd192c..df126ba4a22 100644
--- a/src/mongo/client/connection_string.cpp
+++ b/src/mongo/client/connection_string.cpp
@@ -38,30 +38,32 @@
 
 namespace mongo {
 
-ConnectionString::ConnectionString(const HostAndPort& server) : _type(MASTER) {
+ConnectionString::ConnectionString(const HostAndPort& server) : _type(ConnectionType::kStandalone) {
     _servers.push_back(server);
     _finishInit();
 }
 
-ConnectionString::ConnectionString(StringData setName, std::vector<HostAndPort> servers)
-    : _type(SET), _servers(std::move(servers)), _setName(setName.toString()) {
+ConnectionString::ConnectionString(StringData replicaSetName, std::vector<HostAndPort> servers)
+    : _type(ConnectionType::kReplicaSet),
+      _servers(std::move(servers)),
+      _replicaSetName(replicaSetName.toString()) {
     _finishInit();
 }
 
 // TODO: unify c-tors
 ConnectionString::ConnectionString(ConnectionType type,
                                    const std::string& s,
-                                   const std::string& setName) {
+                                   const std::string& replicaSetName) {
     _type = type;
-    _setName = setName;
+    _replicaSetName = replicaSetName;
     _fillServers(s);
     _finishInit();
 }
 
 ConnectionString::ConnectionString(ConnectionType type,
                                    std::vector<HostAndPort> servers,
-                                   const std::string& setName)
-    : _type(type), _servers(std::move(servers)), _setName(setName) {
+                                   const std::string& replicaSetName)
+    : _type(type), _servers(std::move(servers)), _replicaSetName(replicaSetName) {
     _finishInit();
 }
 
@@ -72,16 +74,20 @@ ConnectionString::ConnectionString(const std::string& s, ConnectionType connType
 }
 
 ConnectionString::ConnectionString(ConnectionType connType) : _type(connType), _string("<local>") {
-    invariant(_type == LOCAL);
+    invariant(_type == ConnectionType::kLocal);
 }
 
-ConnectionString ConnectionString::forReplicaSet(StringData setName,
+ConnectionString ConnectionString::forReplicaSet(StringData replicaSetName,
                                                  std::vector<HostAndPort> servers) {
-    return ConnectionString(setName, std::move(servers));
+    return ConnectionString(replicaSetName, std::move(servers));
+}
+
+ConnectionString ConnectionString::forStandalones(std::vector<HostAndPort> servers) {
+    return ConnectionString(ConnectionType::kStandalone, std::move(servers), "");
 }
 
 ConnectionString ConnectionString::forLocal() {
-    return ConnectionString(LOCAL);
+    return ConnectionString(ConnectionType::kLocal);
 }
 
 // TODO: rewrite parsing  make it more reliable
@@ -93,15 +99,15 @@ void ConnectionString::_fillServers(std::string s) {
     //
 
     if (s.find('$') == 0) {
-        _type = CUSTOM;
+        _type = ConnectionType::kCustom;
     }
 
     std::string::size_type idx = s.find('/');
     if (idx != std::string::npos) {
-        _setName = s.substr(0, idx);
+        _replicaSetName = s.substr(0, idx);
         s = s.substr(idx + 1);
-        if (_type != CUSTOM)
-            _type = SET;
+        if (_type != ConnectionType::kCustom)
+            _type = ConnectionType::kReplicaSet;
     }
 
     while ((idx = s.find(',')) != std::string::npos) {
@@ -111,22 +117,22 @@ void ConnectionString::_fillServers(std::string s) {
 
     _servers.push_back(HostAndPort(s));
 
-    if (_servers.size() == 1 && _type == INVALID) {
-        _type = MASTER;
+    if (_servers.size() == 1 && _type == ConnectionType::kInvalid) {
+        _type = ConnectionType::kStandalone;
     }
 }
 
 void ConnectionString::_finishInit() {
     switch (_type) {
-        case MASTER:
+        case ConnectionType::kStandalone:
             uassert(ErrorCodes::FailedToParse,
-                    "Cannot specify a replica set name for a ConnectionString of type MASTER",
-                    _setName.empty());
+                    "Cannot specify a replica set name for a standalone ConnectionString",
+                    _replicaSetName.empty());
             break;
-        case SET:
+        case ConnectionType::kReplicaSet:
             uassert(ErrorCodes::FailedToParse,
                     "Must specify set name for replica set ConnectionStrings",
-                    !_setName.empty());
+                    !_replicaSetName.empty());
             uassert(ErrorCodes::FailedToParse,
                     "Replica set ConnectionStrings must have at least one server specified",
                     _servers.size() >= 1);
@@ -139,16 +145,16 @@ void ConnectionString::_finishInit() {
 
     // Needed here as well b/c the parsing logic isn't used in all constructors
     // TODO: Refactor so that the parsing logic *is* used in all constructors
-    if (_type == MASTER && _servers.size() > 0) {
+    if (_type == ConnectionType::kStandalone && _servers.size() > 0) {
         if (_servers[0].host().find('$') == 0) {
-            _type = CUSTOM;
+            _type = ConnectionType::kCustom;
         }
     }
 
     std::stringstream ss;
 
-    if (_type == SET) {
-        ss << _setName << "/";
+    if (_type == ConnectionType::kReplicaSet) {
+        ss << _replicaSetName << "/";
     }
 
     for (unsigned i = 0; i < _servers.size(); i++) {
@@ -177,15 +183,15 @@ bool ConnectionString::operator==(const ConnectionString& other) const {
     }
 
     switch (_type) {
-        case INVALID:
+        case ConnectionType::kInvalid:
             return true;
-        case MASTER:
+        case ConnectionType::kStandalone:
             return _servers[0] == other._servers[0];
-        case SET:
-            return _setName == other._setName && _servers == other._servers;
-        case CUSTOM:
+        case ConnectionType::kReplicaSet:
+            return _replicaSetName == other._replicaSetName && _servers == other._servers;
+        case ConnectionType::kCustom:
             return _string == other._string;
-        case LOCAL:
+        case ConnectionType::kLocal:
             return true;
     }
 
@@ -201,7 +207,7 @@ StatusWith<ConnectionString> ConnectionString::parse(const std::string& url) {
 
     // Replica set
     if (i != std::string::npos && i != 0) {
-        return ConnectionString(SET, url.substr(i + 1), url.substr(0, i));
+        return ConnectionString(ConnectionType::kReplicaSet, url.substr(i + 1), url.substr(0, i));
     }
 
     const int numCommas = str::count(url, ',');
@@ -233,15 +239,15 @@ ConnectionString ConnectionString::deserialize(StringData url) {
 
 std::string ConnectionString::typeToString(ConnectionType type) {
     switch (type) {
-        case INVALID:
+        case ConnectionType::kInvalid:
             return "invalid";
-        case MASTER:
-            return "master";
-        case SET:
-            return "set";
-        case CUSTOM:
+        case ConnectionType::kStandalone:
+            return "standalone";
+        case ConnectionType::kReplicaSet:
+            return "replicaSet";
+        case ConnectionType::kCustom:
             return "custom";
-        case LOCAL:
+        case ConnectionType::kLocal:
             return "local";
     }
 
diff --git a/src/mongo/client/connection_string.h b/src/mongo/client/connection_string.h
index 98b66bef986..77f5f73a277 100644
--- a/src/mongo/client/connection_string.h
+++ b/src/mongo/client/connection_string.h
@@ -52,7 +52,7 @@ class MongoURI;
  * samples:
  *    server
  *    server:port
- *    foo/server:port,server:port   SET
+ *    foo/server:port,server:port   kReplicaSet
  *
  * Typical use:
  *
@@ -62,14 +62,20 @@ class MongoURI;
  */
 class ConnectionString {
 public:
-    enum ConnectionType { INVALID, MASTER, SET, CUSTOM, LOCAL };
+    enum class ConnectionType { kInvalid = 0, kStandalone, kReplicaSet, kCustom, kLocal };
 
     ConnectionString() = default;
 
     /**
      * Constructs a connection string representing a replica set.
      */
-    static ConnectionString forReplicaSet(StringData setName, std::vector<HostAndPort> servers);
+    static ConnectionString forReplicaSet(StringData replicaSetName,
+                                          std::vector<HostAndPort> servers);
+
+    /**
+     * Constructs a connection string representing a list of standalone servers.
+     */
+    static ConnectionString forStandalones(std::vector<HostAndPort> servers);
 
     /**
      * Constructs a local connection string.
@@ -77,34 +83,42 @@ public:
     static ConnectionString forLocal();
 
     /**
-     * Creates a MASTER connection string with the specified server.
+     * Creates a standalone connection string with the specified server.
      */
     explicit ConnectionString(const HostAndPort& server);
 
     /**
-     * Creates a connection string from an unparsed list of servers, type, and setName.
+     * Creates a connection string from an unparsed list of servers, type, and replicaSetName.
      */
-    ConnectionString(ConnectionType type, const std::string& s, const std::string& setName);
+    ConnectionString(ConnectionType type, const std::string& s, const std::string& replicaSetName);
 
     /**
-     * Creates a connection string from a pre-parsed list of servers, type, and setName.
+     * Creates a connection string from a pre-parsed list of servers, type, and replicaSetName.
      */
     ConnectionString(ConnectionType type,
                      std::vector<HostAndPort> servers,
-                     const std::string& setName);
+                     const std::string& replicaSetName);
 
     ConnectionString(const std::string& s, ConnectionType connType);
 
     bool isValid() const {
-        return _type != INVALID;
+        return _type != ConnectionType::kInvalid;
+    }
+
+    explicit operator bool() const {
+        return isValid();
     }
 
     const std::string& toString() const {
         return _string;
     }
 
+    const std::string& getReplicaSetName() const {
+        return _replicaSetName;
+    }
+
     const std::string& getSetName() const {
-        return _setName;
+        return getReplicaSetName();
     }
 
     const std::vector<HostAndPort>& getServers() const {
@@ -187,22 +201,25 @@ public:
 
 private:
     /**
-     * Creates a SET connection string with the specified set name and servers.
+     * Creates a replica set connection string with the specified name and servers.
      */
-    ConnectionString(StringData setName, std::vector<HostAndPort> servers);
+    ConnectionString(StringData replicaSetName, std::vector<HostAndPort> servers);
 
     /**
-     * Creates a connection string with the specified type. Used for creating LOCAL strings.
+     * Creates a connection string with the specified type.
+     *
+     * This ctor is mostly used to create ConnectionStrings to the current node with
+     * ConnectionType::kLocal.
      */
     explicit ConnectionString(ConnectionType connType);
 
     void _fillServers(std::string s);
     void _finishInit();
 
-    ConnectionType _type{INVALID};
+    ConnectionType _type{ConnectionType::kInvalid};
     std::vector<HostAndPort> _servers;
     std::string _string;
-    std::string _setName;
+    std::string _replicaSetName;
 
     static Mutex _connectHookMutex;
     static ConnectionHook* _connectHook;
@@ -218,4 +235,14 @@ inline StringBuilder& operator<<(StringBuilder& sb, const ConnectionString& cs)
     return sb;
 }
 
+inline std::ostream& operator<<(std::ostream& ss, const ConnectionString::ConnectionType& ct) {
+    ss << ConnectionString::typeToString(ct);
+    return ss;
+}
+
+inline StringBuilder& operator<<(StringBuilder& sb, const ConnectionString::ConnectionType& ct) {
+    sb << ConnectionString::typeToString(ct);
+    return sb;
+}
+
 }  // namespace mongo
diff --git a/src/mongo/client/connection_string_connect.cpp b/src/mongo/client/connection_string_connect.cpp
index 735fc47d2af..ae4bf55d6fd 100644
--- a/src/mongo/client/connection_string_connect.cpp
+++ b/src/mongo/client/connection_string_connect.cpp
@@ -58,7 +58,7 @@ std::unique_ptr<DBClientBase> ConnectionString::connect(
     }
 
     switch (_type) {
-        case MASTER: {
+        case ConnectionType::kStandalone: {
             for (const auto& server : _servers) {
                 auto c = std::make_unique<DBClientConnection>(
                     true, 0, newURI, DBClientConnection::HandshakeValidationHook(), apiParameters);
@@ -78,8 +78,8 @@ std::unique_ptr<DBClientBase> ConnectionString::connect(
             return nullptr;
         }
 
-        case SET: {
-            auto set = std::make_unique<DBClientReplicaSet>(_setName,
+        case ConnectionType::kReplicaSet: {
+            auto set = std::make_unique<DBClientReplicaSet>(_replicaSetName,
                                                             _servers,
                                                             applicationName,
                                                             socketTimeout,
@@ -93,7 +93,7 @@ std::unique_ptr<DBClientBase> ConnectionString::connect(
             return std::move(set);
         }
 
-        case CUSTOM: {
+        case ConnectionType::kCustom: {
             // Lock in case other things are modifying this at the same time
             stdx::lock_guard<Latch> lk(_connectHookMutex);
 
@@ -118,8 +118,8 @@ std::unique_ptr<DBClientBase> ConnectionString::connect(
             return replacementConn;
         }
 
-        case LOCAL:
-        case INVALID:
+        case ConnectionType::kLocal:
+        case ConnectionType::kInvalid:
             MONGO_UNREACHABLE;
     }
 
diff --git a/src/mongo/client/connection_string_test.cpp b/src/mongo/client/connection_string_test.cpp
index fe09c3912de..355a62c0910 100644
--- a/src/mongo/client/connection_string_test.cpp
+++ b/src/mongo/client/connection_string_test.cpp
@@ -38,7 +38,7 @@ namespace {
 
 using unittest::assertGet;
 
-TEST(ConnectionString, EqualityOperatorMaster) {
+TEST(ConnectionString, EqualityOperatorStandalone) {
     const auto cs = assertGet(ConnectionString::parse("TestHostA:12345"));
     ASSERT(cs == assertGet(ConnectionString::parse("TestHostA:12345")));
     ASSERT_FALSE(cs != assertGet(ConnectionString::parse("TestHostA:12345")));
diff --git a/src/mongo/client/connpool.cpp b/src/mongo/client/connpool.cpp
index 6adf8c75645..f742a8dcef8 100644
--- a/src/mongo/client/connpool.cpp
+++ b/src/mongo/client/connpool.cpp
@@ -80,7 +80,7 @@ using std::vector;
 PoolForHost::PoolForHost()
     : _created(0),
       _minValidCreationTimeMicroSec(0),
-      _type(ConnectionString::INVALID),
+      _type(ConnectionString::ConnectionType::kInvalid),
       _maxPoolSize(kPoolSizeUnlimited),
       _maxInUse(kDefaultMaxInUse),
       _checkedOut(0),
@@ -701,7 +701,7 @@ void ScopedDbConnection::_setSocketTimeout() {
     if (!_conn)
         return;
 
-    if (_conn->type() == ConnectionString::MASTER)
+    if (_conn->type() == ConnectionString::ConnectionType::kStandalone)
         static_cast<DBClientConnection*>(_conn)->setSoTimeout(_socketTimeoutSecs);
 }
 
diff --git a/src/mongo/client/dbclient_connection.h b/src/mongo/client/dbclient_connection.h
index cff4082d09e..3d80c9c371b 100644
--- a/src/mongo/client/dbclient_connection.h
+++ b/src/mongo/client/dbclient_connection.h
@@ -244,7 +244,7 @@ public:
               bool assertOk,
               std::string* actualServer) override;
     ConnectionString::ConnectionType type() const override {
-        return ConnectionString::MASTER;
+        return ConnectionString::ConnectionType::kStandalone;
     }
     void setSoTimeout(double timeout);
     double getSoTimeout() const override {
diff --git a/src/mongo/client/dbclient_cursor.cpp b/src/mongo/client/dbclient_cursor.cpp
index 34fa4f0f272..8031febcffa 100644
--- a/src/mongo/client/dbclient_cursor.cpp
+++ b/src/mongo/client/dbclient_cursor.cpp
@@ -503,7 +503,7 @@ void DBClientCursor::attach(AScopedConnection* conn) {
     verify(conn);
     verify(conn->get());
 
-    if (conn->get()->type() == ConnectionString::SET) {
+    if (conn->get()->type() == ConnectionString::ConnectionType::kReplicaSet) {
         if (_lazyHost.size() > 0)
             _scopedHost = _lazyHost;
         else if (_client)
diff --git a/src/mongo/client/dbclient_rs.h b/src/mongo/client/dbclient_rs.h
index 64a9ddffb03..733eddb0dc3 100644
--- a/src/mongo/client/dbclient_rs.h
+++ b/src/mongo/client/dbclient_rs.h
@@ -203,7 +203,7 @@ public:
     std::string getServerAddress() const override;
 
     ConnectionString::ConnectionType type() const override {
-        return ConnectionString::SET;
+        return ConnectionString::ConnectionType::kReplicaSet;
     }
     bool lazySupported() const override {
         return true;
diff --git a/src/mongo/client/mongo_uri.cpp b/src/mongo/client/mongo_uri.cpp
index 08454c6b3f7..e2b0af43b7c 100644
--- a/src/mongo/client/mongo_uri.cpp
+++ b/src/mongo/client/mongo_uri.cpp
@@ -456,12 +456,12 @@ MongoURI MongoURI::parseImpl(StringData url) {
     auto options =
         addTXTOptions(parseOptions(connectionOptions, url), canonicalHost, url, isSeedlist);
 
-    // If a replica set option was specified, store it in the 'setName' field.
+    // If a replica set option was specified, store it in the 'replicaSetName' field.
     auto optIter = options.find("replicaSet");
-    std::string setName;
+    std::string replicaSetName;
     if (optIter != end(options)) {
-        setName = optIter->second;
-        invariant(!setName.empty());
+        replicaSetName = optIter->second;
+        invariant(!replicaSetName.empty());
     }
 
     // If an appName option was specified, validate that is 128 bytes or less.
@@ -500,8 +500,9 @@ MongoURI MongoURI::parseImpl(StringData url) {
         }
     }
 
-    ConnectionString cs(
-        setName.empty() ? ConnectionString::MASTER : ConnectionString::SET, servers, setName);
+    auto cs = replicaSetName.empty()
+        ? ConnectionString::forStandalones(std::move(servers))
+        : ConnectionString::forReplicaSet(replicaSetName, std::move(servers));
     return MongoURI(std::move(cs),
                     username,
                     password,
diff --git a/src/mongo/client/mongo_uri.h b/src/mongo/client/mongo_uri.h
index 26546ed7af5..4a7ca89126a 100644
--- a/src/mongo/client/mongo_uri.h
+++ b/src/mongo/client/mongo_uri.h
@@ -208,6 +208,10 @@ public:
         return _connectString.isValid();
     }
 
+    explicit operator bool() const {
+        return isValid();
+    }
+
     const ConnectionString& connectionString() const {
         return _connectString;
     }
@@ -216,10 +220,14 @@ public:
         return _connectString.toString();
     }
 
-    const std::string& getSetName() const {
+    const std::string& getReplicaSetName() const {
         return _connectString.getSetName();
     }
 
+    const std::string& getSetName() const {
+        return getReplicaSetName();
+    }
+
     const std::vector<HostAndPort>& getServers() const {
         return _connectString.getServers();
     }
@@ -240,7 +248,7 @@ public:
 
     // If you are trying to clone a URI (including its options/auth information) for a single
     // server (say a member of a replica-set), you can pass in its HostAndPort information to
-    // get a new URI with the same info, except type() will be MASTER and getServers() will
+    // get a new URI with the same info, except type() will be kStandalone and getServers() will
     // be the single host you pass in.
     MongoURI cloneURIForServer(HostAndPort hostAndPort, StringData applicationName) const {
         auto out = *this;
diff --git a/src/mongo/client/mongo_uri_test.cpp b/src/mongo/client/mongo_uri_test.cpp
index b7f1df41482..f8c3027fb20 100644
--- a/src/mongo/client/mongo_uri_test.cpp
+++ b/src/mongo/client/mongo_uri_test.cpp
@@ -105,8 +105,8 @@ void compareOptions(size_t lineNumber,
                                                       << " data on line: " << lineNumber << uri;
 }
 
-const ConnectionString::ConnectionType kMaster = ConnectionString::MASTER;
-const ConnectionString::ConnectionType kSet = ConnectionString::SET;
+const ConnectionString::ConnectionType kMaster = ConnectionString::ConnectionType::kStandalone;
+const ConnectionString::ConnectionType kReplicaSet = ConnectionString::ConnectionType::kReplicaSet;
 
 const URITestCase validCases[] = {
 
@@ -155,7 +155,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@127.0.0.1,127.0.0.2/dbname?a=b&replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"a", "b"}, {"replicaSet", "replName"}},
@@ -166,7 +166,7 @@ const URITestCase validCases[] = {
      "dbname?a=b&replicaSet=replName",
      "needs encoding%#!<>",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"a", "b"}, {"replicaSet", "replName"}},
@@ -177,7 +177,7 @@ const URITestCase validCases[] = {
      "db@name?a=b&replicaSet=replName",
      "needs encoding%#!<>",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"a", "b"}, {"replicaSet", "replName"}},
@@ -188,7 +188,7 @@ const URITestCase validCases[] = {
      "dbname?a=b&replicaSet=replName",
      "user",
      "needs encoding%#!<>",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"a", "b"}, {"replicaSet", "replName"}},
@@ -198,7 +198,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@127.0.0.1,127.0.0.2/dbname?a=b&replicaSet=needs%20encoding%25%23!%3C%3E",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "needs encoding%#!<>",
      2,
      {{"a", "b"}, {"replicaSet", "needs encoding%#!<>"}},
@@ -208,7 +208,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@127.0.0.1,127.0.0.2/needsencoding%40hello?a=b&replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"a", "b"}, {"replicaSet", "replName"}},
@@ -218,7 +218,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@127.0.0.1,127.0.0.2/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -228,7 +228,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@127.0.0.1,127.0.0.2/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -238,7 +238,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@127.0.0.1,127.0.0.2/?replicaset=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -248,7 +248,7 @@ const URITestCase validCases[] = {
     {"mongodb://127.0.0.1,127.0.0.2/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -258,7 +258,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@127.0.0.1:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -268,7 +268,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@127.0.0.1:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -278,7 +278,7 @@ const URITestCase validCases[] = {
     {"mongodb://127.0.0.1:1234,127.0.0.1:1234/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -316,7 +316,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@[::1],127.0.0.2/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -326,7 +326,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@[::1],127.0.0.2/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -336,7 +336,7 @@ const URITestCase validCases[] = {
     {"mongodb://[::1],127.0.0.2/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -346,7 +346,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@[::1]:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -356,7 +356,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@[::1]:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -366,7 +366,7 @@ const URITestCase validCases[] = {
     {"mongodb://[::1]:1234,[::1]:1234/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -404,7 +404,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@[::1],127.0.0.2/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -414,7 +414,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@[::1],127.0.0.2/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -424,7 +424,7 @@ const URITestCase validCases[] = {
     {"mongodb://[::1],127.0.0.2/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -434,7 +434,7 @@ const URITestCase validCases[] = {
     {"mongodb://user:pwd@[::1]:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "pwd",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -444,7 +444,7 @@ const URITestCase validCases[] = {
     {"mongodb://user@[::1]:1234,127.0.0.2:1234/?replicaSet=replName",
      "user",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -454,7 +454,7 @@ const URITestCase validCases[] = {
     {"mongodb://[::1]:1234,[::1]:1234/dbName?foo=a&c=b&replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"foo", "a"}, {"c", "b"}, {"replicaSet", "replName"}},
@@ -486,7 +486,7 @@ const URITestCase validCases[] = {
     {"mongodb://%2Ftmp%2Fmongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock/?replicaSet=replName",
      "",
      "",
-     kSet,
+     kReplicaSet,
      "replName",
      2,
      {{"replicaSet", "replName"}},
@@ -609,7 +609,7 @@ void testValidURIFormat(URITestCase testCase) {
     ASSERT_EQ(testCase.uname, result.getUser());
     ASSERT_EQ(testCase.password, result.getPassword());
     ASSERT_EQ(testCase.type, result.type());
-    ASSERT_EQ(testCase.setname, result.getSetName());
+    ASSERT_EQ(testCase.setname, result.getReplicaSetName());
     ASSERT_EQ(testCase.numservers, result.getServers().size());
     compareOptions(0, testCase.URI, result.getOptions(), testCase.options);
     ASSERT_EQ(testCase.database, result.getDatabase());
@@ -657,8 +657,8 @@ TEST(MongoURI, CloneURIForServer) {
     ASSERT_OK(sw_uri.getStatus());
 
     auto uri = sw_uri.getValue();
-    ASSERT_EQ(uri.type(), kSet);
-    ASSERT_EQ(uri.getSetName(), "rs1");
+    ASSERT_EQ(uri.type(), kReplicaSet);
+    ASSERT_EQ(uri.getReplicaSetName(), "rs1");
     ASSERT_EQ(uri.getServers().size(), static_cast<std::size_t>(3));
 
     auto& uriOptions = uri.getOptions();
@@ -667,7 +667,7 @@ TEST(MongoURI, CloneURIForServer) {
     auto clonedURI = uri.cloneURIForServer(HostAndPort{"localhost:27020"}, StringData());
 
     ASSERT_EQ(clonedURI.type(), kMaster);
-    ASSERT_TRUE(clonedURI.getSetName().empty());
+    ASSERT_TRUE(clonedURI.getReplicaSetName().empty());
     ASSERT_EQ(clonedURI.getServers().size(), static_cast<std::size_t>(1));
     auto& clonedURIOptions = clonedURI.getOptions();
     ASSERT_EQ(clonedURIOptions.at("ssl"), "true");
@@ -754,7 +754,7 @@ TEST(MongoURI, specTests) {
                     if (!replsetElement.eoo()) {
                         ASSERT_EQ(replsetElement.type(), String);
                         setName = replsetElement.String();
-                        connectionType = kSet;
+                        connectionType = kReplicaSet;
                     }
 
                     for (auto&& field : optionsElement.Obj()) {
diff --git a/src/mongo/client/remote_command_targeter_factory_impl.cpp b/src/mongo/client/remote_command_targeter_factory_impl.cpp
index a0a1df7b6a7..c140a184a31 100644
--- a/src/mongo/client/remote_command_targeter_factory_impl.cpp
+++ b/src/mongo/client/remote_command_targeter_factory_impl.cpp
@@ -48,16 +48,16 @@ RemoteCommandTargeterFactoryImpl::~RemoteCommandTargeterFactoryImpl() = default;
 std::unique_ptr<RemoteCommandTargeter> RemoteCommandTargeterFactoryImpl::create(
     const ConnectionString& connStr) {
     switch (connStr.type()) {
-        case ConnectionString::MASTER:
-        case ConnectionString::CUSTOM:
+        case ConnectionString::ConnectionType::kStandalone:
+        case ConnectionString::ConnectionType::kCustom:
             invariant(connStr.getServers().size() == 1);
             return std::make_unique<RemoteCommandTargeterStandalone>(connStr.getServers().front());
-        case ConnectionString::SET:
+        case ConnectionString::ConnectionType::kReplicaSet:
             return std::make_unique<RemoteCommandTargeterRS>(connStr.getSetName(),
                                                              connStr.getServers());
         // These connections should never be seen
-        case ConnectionString::INVALID:
-        case ConnectionString::LOCAL:
+        case ConnectionString::ConnectionType::kInvalid:
+        case ConnectionString::ConnectionType::kLocal:
             MONGO_UNREACHABLE;
     }
     MONGO_UNREACHABLE;
diff --git a/src/mongo/client/remote_command_targeter_factory_impl.h b/src/mongo/client/remote_command_targeter_factory_impl.h
index df8494576db..235947402a7 100644
--- a/src/mongo/client/remote_command_targeter_factory_impl.h
+++ b/src/mongo/client/remote_command_targeter_factory_impl.h
@@ -35,9 +35,9 @@ namespace mongo {
 
 /**
  * Targeter factory that instantiates remote command targeters based on the type of the
- * connection. It will return RemoteCommandTargeterStandalone for a single node (MASTER) or
- * custom (CUSTOM) connection string and RemoteCommandTargeterRS for a SET connection string.
- * All other connection strings are not supported and will cause a failed invariant error.
+ * connection. It will return RemoteCommandTargeterStandalone for a single node (kStandalone) or
+ * custom (kCustom) connection string and RemoteCommandTargeterRS for a kReplicaSet connection
+ * string. All other connection strings are not supported and will cause a failed invariant error.
  */
 class RemoteCommandTargeterFactoryImpl final : public RemoteCommandTargeterFactory {
 public:
diff --git a/src/mongo/client/replica_set_monitor_manager.cpp b/src/mongo/client/replica_set_monitor_manager.cpp
index 0a1b1818215..732c8867b67 100644
--- a/src/mongo/client/replica_set_monitor_manager.cpp
+++ b/src/mongo/client/replica_set_monitor_manager.cpp
@@ -170,7 +170,7 @@ shared_ptr<ReplicaSetMonitor> ReplicaSetMonitorManager::getOrCreateMonitor(
 }
 
 shared_ptr<ReplicaSetMonitor> ReplicaSetMonitorManager::getOrCreateMonitor(const MongoURI& uri) {
-    invariant(uri.type() == ConnectionString::SET);
+    invariant(uri.type() == ConnectionString::ConnectionType::kReplicaSet);
     stdx::lock_guard<Latch> lk(_mutex);
     uassert(ErrorCodes::ShutdownInProgress,
             str::stream() << "Unable to get monitor for '" << uri << "' due to shutdown",
diff --git a/src/mongo/db/dbdirectclient.cpp b/src/mongo/db/dbdirectclient.cpp
index bb1f5553906..04910a0faad 100644
--- a/src/mongo/db/dbdirectclient.cpp
+++ b/src/mongo/db/dbdirectclient.cpp
@@ -110,7 +110,7 @@ bool DBDirectClient::isReplicaSetMember() const {
 }
 
 ConnectionString::ConnectionType DBDirectClient::type() const {
-    return ConnectionString::MASTER;
+    return ConnectionString::ConnectionType::kStandalone;
 }
 
 double DBDirectClient::getSoTimeout() const {
diff --git a/src/mongo/db/s/config/sharding_catalog_manager_add_shard_test.cpp b/src/mongo/db/s/config/sharding_catalog_manager_add_shard_test.cpp
index 777b23622ee..a7b48597d72 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager_add_shard_test.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager_add_shard_test.cpp
@@ -521,8 +521,8 @@ TEST_F(AddShardTest, StandaloneGenerateName) {
 TEST_F(AddShardTest, AddSCCCConnectionStringAsShard) {
     std::unique_ptr<RemoteCommandTargeterMock> targeter(
         std::make_unique<RemoteCommandTargeterMock>());
-    auto invalidConn =
-        ConnectionString("host1:12345,host2:12345,host3:12345", ConnectionString::INVALID);
+    auto invalidConn = ConnectionString("host1:12345,host2:12345,host3:12345",
+                                        ConnectionString::ConnectionType::kInvalid);
     targeter->setConnectionStringReturnValue(invalidConn);
 
     auto future = launchAsync([this, invalidConn] {
diff --git a/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp b/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
index b82c0b908e5..3fdb7828254 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
@@ -236,7 +236,8 @@ StatusWith<boost::optional<ShardType>> ShardingCatalogManager::_checkIfShardExis
             if (proposedShardConnectionString.type() != existingShardConnStr.type()) {
                 return false;
             }
-            if (proposedShardConnectionString.type() == ConnectionString::SET &&
+            if (proposedShardConnectionString.type() ==
+                    ConnectionString::ConnectionType::kReplicaSet &&
                 proposedShardConnectionString.getSetName() != existingShardConnStr.getSetName()) {
                 return false;
             }
@@ -246,8 +247,8 @@ StatusWith<boost::optional<ShardType>> ShardingCatalogManager::_checkIfShardExis
             return true;
         };
 
-        if (existingShardConnStr.type() == ConnectionString::SET &&
-            proposedShardConnectionString.type() == ConnectionString::SET &&
+        if (existingShardConnStr.type() == ConnectionString::ConnectionType::kReplicaSet &&
+            proposedShardConnectionString.type() == ConnectionString::ConnectionType::kReplicaSet &&
             existingShardConnStr.getSetName() == proposedShardConnectionString.getSetName()) {
             // An existing shard has the same replica set name as the shard being added.
             // If the options aren't the same, then this is an error,
@@ -533,7 +534,7 @@ StatusWith<std::string> ShardingCatalogManager::addShard(
     const std::string* shardProposedName,
     const ConnectionString& shardConnectionString,
     const long long maxSize) {
-    if (shardConnectionString.type() == ConnectionString::INVALID) {
+    if (!shardConnectionString) {
         return {ErrorCodes::BadValue, "Invalid connection string"};
     }
 
@@ -565,7 +566,7 @@ StatusWith<std::string> ShardingCatalogManager::addShard(
     auto targeter = shard->getTargeter();
 
     auto stopMonitoringGuard = makeGuard([&] {
-        if (shardConnectionString.type() == ConnectionString::SET) {
+        if (shardConnectionString.type() == ConnectionString::ConnectionType::kReplicaSet) {
             // This is a workaround for the case were we could have some bad shard being
             // requested to be added and we put that bad connection string on the global replica set
             // monitor registry. It needs to be cleaned up so that when a correct replica set is
diff --git a/src/mongo/db/s/sharding_initialization_mongod.cpp b/src/mongo/db/s/sharding_initialization_mongod.cpp
index 65265781d1e..777985d1eb4 100644
--- a/src/mongo/db/s/sharding_initialization_mongod.cpp
+++ b/src/mongo/db/s/sharding_initialization_mongod.cpp
@@ -442,7 +442,9 @@ void ShardingInitializationMongoD::initializeFromShardIdentity(
         uassert(40372, "", shardingState->clusterId() == shardIdentity.getClusterId());
 
         auto prevConfigsvrConnStr = shardRegistry->getConfigServerConnectionString();
-        uassert(40373, "", prevConfigsvrConnStr.type() == ConnectionString::SET);
+        uassert(40373,
+                "",
+                prevConfigsvrConnStr.type() == ConnectionString::ConnectionType::kReplicaSet);
         uassert(40374, "", prevConfigsvrConnStr.getSetName() == configSvrConnStr.getSetName());
 
         return;
@@ -531,9 +533,9 @@ void initializeGlobalShardingStateForMongoD(OperationContext* opCtx,
     };
 
     ShardFactory::BuildersMap buildersMap{
-        {ConnectionString::SET, std::move(setBuilder)},
-        {ConnectionString::MASTER, std::move(masterBuilder)},
-        {ConnectionString::LOCAL, std::move(localBuilder)},
+        {ConnectionString::ConnectionType::kReplicaSet, std::move(setBuilder)},
+        {ConnectionString::ConnectionType::kStandalone, std::move(masterBuilder)},
+        {ConnectionString::ConnectionType::kLocal, std::move(localBuilder)},
     };
 
     auto shardFactory =
@@ -571,9 +573,7 @@ void initializeGlobalShardingStateForMongoD(OperationContext* opCtx,
             catCache->invalidateEntriesThatReferenceShard(removedShard);
         }};
 
-    uassert(ErrorCodes::BadValue,
-            "Unrecognized connection string.",
-            configCS.type() != ConnectionString::INVALID);
+    uassert(ErrorCodes::BadValue, "Unrecognized connection string.", configCS);
 
     auto shardRegistry = std::make_unique<ShardRegistry>(
         std::move(shardFactory), configCS, std::move(shardRemovalHooks));
diff --git a/src/mongo/db/s/sharding_initialization_mongod_test.cpp b/src/mongo/db/s/sharding_initialization_mongod_test.cpp
index a724a245f84..44b90529a89 100644
--- a/src/mongo/db/s/sharding_initialization_mongod_test.cpp
+++ b/src/mongo/db/s/sharding_initialization_mongod_test.cpp
@@ -172,7 +172,7 @@ TEST_F(ShardingInitializationMongoDTest, ValidShardIdentitySucceeds) {
 
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(OID::gen());
 
@@ -189,7 +189,7 @@ TEST_F(ShardingInitializationMongoDTest, InitWhilePreviouslyInErrorStateWillStay
 
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(OID::gen());
 
@@ -222,7 +222,7 @@ TEST_F(ShardingInitializationMongoDTest, InitializeAgainWithMatchingShardIdentit
     auto clusterID = OID::gen();
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(clusterID);
 
@@ -230,7 +230,7 @@ TEST_F(ShardingInitializationMongoDTest, InitializeAgainWithMatchingShardIdentit
 
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity2.setShardName(kShardName);
     shardIdentity2.setClusterId(clusterID);
 
@@ -255,7 +255,7 @@ TEST_F(ShardingInitializationMongoDTest, InitializeAgainWithMatchingReplSetNameS
     auto clusterID = OID::gen();
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(clusterID);
 
@@ -263,7 +263,7 @@ TEST_F(ShardingInitializationMongoDTest, InitializeAgainWithMatchingReplSetNameS
 
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "b:2,c:3", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "b:2,c:3", "config"));
     shardIdentity2.setShardName(kShardName);
     shardIdentity2.setClusterId(clusterID);
 
@@ -319,7 +319,7 @@ TEST_F(ShardingInitializationMongoDTest,
     serverGlobalParams.overrideShardIdentity = [] {
         ShardIdentityType shardIdentity;
         shardIdentity.setConfigsvrConnectionString(
-            ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+            ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
         shardIdentity.setShardName(kShardName);
         shardIdentity.setClusterId(OID::gen());
         ASSERT_OK(shardIdentity.validate());
@@ -363,7 +363,7 @@ TEST_F(ShardingInitializationMongoDTest,
     serverGlobalParams.overrideShardIdentity = [] {
         ShardIdentityType shardIdentity;
         shardIdentity.setConfigsvrConnectionString(
-            ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+            ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
         shardIdentity.setShardName(kShardName);
         shardIdentity.setClusterId(OID::gen());
         ASSERT_OK(shardIdentity.validate());
@@ -406,7 +406,7 @@ TEST_F(ShardingInitializationMongoDTest,
     serverGlobalParams.overrideShardIdentity = [] {
         ShardIdentityType shardIdentity;
         shardIdentity.setConfigsvrConnectionString(
-            ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+            ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
         shardIdentity.setShardName(kShardName);
         shardIdentity.setClusterId(OID::gen());
         ASSERT_OK(shardIdentity.validate());
@@ -469,8 +469,8 @@ TEST_F(ShardingInitializationMongoDTest,
 
         BSONObj validShardIdentity = [&] {
             ShardIdentityType shardIdentity;
-            shardIdentity.setConfigsvrConnectionString(
-                ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+            shardIdentity.setConfigsvrConnectionString(ConnectionString(
+                ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
             shardIdentity.setShardName(kShardName);
             shardIdentity.setClusterId(OID::gen());
             ASSERT_OK(shardIdentity.validate());
@@ -516,7 +516,7 @@ TEST_F(ShardingInitializationMongoDTest,
     BSONObj validShardIdentity = [&] {
         ShardIdentityType shardIdentity;
         shardIdentity.setConfigsvrConnectionString(
-            ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+            ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
         shardIdentity.setShardName(kShardName);
         shardIdentity.setClusterId(OID::gen());
         ASSERT_OK(shardIdentity.validate());
diff --git a/src/mongo/db/s/sharding_initialization_op_observer_test.cpp b/src/mongo/db/s/sharding_initialization_op_observer_test.cpp
index 563a6325454..019394f91e9 100644
--- a/src/mongo/db/s/sharding_initialization_op_observer_test.cpp
+++ b/src/mongo/db/s/sharding_initialization_op_observer_test.cpp
@@ -90,7 +90,7 @@ private:
 TEST_F(ShardingInitializationOpObserverTest, GlobalInitGetsCalledAfterWriteCommits) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(OID::gen());
 
@@ -102,7 +102,7 @@ TEST_F(ShardingInitializationOpObserverTest, GlobalInitGetsCalledAfterWriteCommi
 TEST_F(ShardingInitializationOpObserverTest, GlobalInitDoesntGetCalledIfWriteAborts) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(OID::gen());
 
@@ -128,7 +128,7 @@ TEST_F(ShardingInitializationOpObserverTest, GlobalInitDoesntGetCalledIfWriteAbo
 TEST_F(ShardingInitializationOpObserverTest, GlobalInitDoesntGetsCalledIfNSIsNotForShardIdentity) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnectionString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
+        ConnectionString(ConnectionString::ConnectionType::kReplicaSet, "a:1,b:2", "config"));
     shardIdentity.setShardName(kShardName);
     shardIdentity.setClusterId(OID::gen());
 
diff --git a/src/mongo/db/s/sharding_mongod_test_fixture.cpp b/src/mongo/db/s/sharding_mongod_test_fixture.cpp
index 78bd0f861ae..d0ccaa291f8 100644
--- a/src/mongo/db/s/sharding_mongod_test_fixture.cpp
+++ b/src/mongo/db/s/sharding_mongod_test_fixture.cpp
@@ -192,14 +192,15 @@ std::unique_ptr<ShardRegistry> ShardingMongodTestFixture::makeShardRegistry(
         return std::make_unique<ShardRemote>(shardId, connStr, targeterFactoryPtr->create(connStr));
     };
 
-    ShardFactory::BuilderCallable masterBuilder = [targeterFactoryPtr](
-                                                      const ShardId& shardId,
-                                                      const ConnectionString& connStr) {
+    ShardFactory::BuilderCallable standaloneBuilder = [targeterFactoryPtr](
+                                                          const ShardId& shardId,
+                                                          const ConnectionString& connStr) {
         return std::make_unique<ShardRemote>(shardId, connStr, targeterFactoryPtr->create(connStr));
     };
 
-    ShardFactory::BuildersMap buildersMap{{ConnectionString::SET, std::move(setBuilder)},
-                                          {ConnectionString::MASTER, std::move(masterBuilder)}};
+    ShardFactory::BuildersMap buildersMap{
+        {ConnectionString::ConnectionType::kReplicaSet, std::move(setBuilder)},
+        {ConnectionString::ConnectionType::kStandalone, std::move(standaloneBuilder)}};
 
     // Only config servers use ShardLocal for now.
     if (serverGlobalParams.clusterRole == ClusterRole::ConfigServer) {
@@ -209,7 +210,7 @@ std::unique_ptr<ShardRegistry> ShardingMongodTestFixture::makeShardRegistry(
         };
         buildersMap.insert(
             std::pair<ConnectionString::ConnectionType, ShardFactory::BuilderCallable>(
-                ConnectionString::LOCAL, std::move(localBuilder)));
+                ConnectionString::ConnectionType::kLocal, std::move(localBuilder)));
     }
 
     auto shardFactory =
diff --git a/src/mongo/db/s/type_shard_identity.cpp b/src/mongo/db/s/type_shard_identity.cpp
index 773333f59e5..673636f01b1 100644
--- a/src/mongo/db/s/type_shard_identity.cpp
+++ b/src/mongo/db/s/type_shard_identity.cpp
@@ -52,7 +52,7 @@ StatusWith<ShardIdentityType> ShardIdentityType::fromShardIdentityDocument(const
             ShardIdentity::parse(IDLParserErrorContext("ShardIdentity"), shardIdentityBSON);
 
         const auto& configsvrConnStr = shardIdentity.getConfigsvrConnectionString();
-        if (configsvrConnStr.type() != ConnectionString::SET) {
+        if (configsvrConnStr.type() != ConnectionString::ConnectionType::kReplicaSet) {
             return Status(ErrorCodes::UnsupportedFormat,
                           str::stream()
                               << "config server connection string can only be replica sets: "
@@ -67,7 +67,7 @@ StatusWith<ShardIdentityType> ShardIdentityType::fromShardIdentityDocument(const
 
 Status ShardIdentityType::validate() const {
     const auto& configsvrConnStr = getConfigsvrConnectionString();
-    if (configsvrConnStr.type() != ConnectionString::SET) {
+    if (configsvrConnStr.type() != ConnectionString::ConnectionType::kReplicaSet) {
         return {ErrorCodes::UnsupportedFormat,
                 str::stream() << "config connection string can only be replica sets, got "
                               << ConnectionString::typeToString(configsvrConnStr.type())};
diff --git a/src/mongo/dbtests/clienttests.cpp b/src/mongo/dbtests/clienttests.cpp
index f17326bfbf3..e847a3b2fad 100644
--- a/src/mongo/dbtests/clienttests.cpp
+++ b/src/mongo/dbtests/clienttests.cpp
@@ -232,8 +232,8 @@ class ConnectionStringTests {
 public:
     void run() {
         {
-            ConnectionString s("a/b,c,d", ConnectionString::SET);
-            ASSERT_EQUALS(ConnectionString::SET, s.type());
+            ConnectionString s("a/b,c,d", ConnectionString::ConnectionType::kReplicaSet);
+            ASSERT_EQUALS(ConnectionString::ConnectionType::kReplicaSet, s.type());
             ASSERT_EQUALS("a", s.getSetName());
             vector<HostAndPort> v = s.getServers();
             ASSERT_EQUALS(3U, v.size());
diff --git a/src/mongo/dbtests/mock/mock_conn_registry.cpp b/src/mongo/dbtests/mock/mock_conn_registry.cpp
index 1847aeaa01f..37d9df06ceb 100644
--- a/src/mongo/dbtests/mock/mock_conn_registry.cpp
+++ b/src/mongo/dbtests/mock/mock_conn_registry.cpp
@@ -107,7 +107,7 @@ std::unique_ptr<mongo::DBClientBase> MockConnRegistry::MockConnHook::connect(
     auto conn = _registry->connect(hostName);
 
     if (!conn->connect(hostName.c_str(), StringData(), errmsg)) {
-        // mimic ConnectionString::connect for MASTER type connection to return NULL
+        // mimic ConnectionString::connect for kStandalone type connection to return NULL
         // if the destination is unreachable.
         return nullptr;
     }
diff --git a/src/mongo/dbtests/mock/mock_dbclient_connection.cpp b/src/mongo/dbtests/mock/mock_dbclient_connection.cpp
index 55d428a94c5..ec17681e12e 100644
--- a/src/mongo/dbtests/mock/mock_dbclient_connection.cpp
+++ b/src/mongo/dbtests/mock/mock_dbclient_connection.cpp
@@ -173,7 +173,7 @@ std::unique_ptr<mongo::DBClientCursor> MockDBClientConnection::query(
 }
 
 mongo::ConnectionString::ConnectionType MockDBClientConnection::type() const {
-    return mongo::ConnectionString::CUSTOM;
+    return mongo::ConnectionString::ConnectionType::kCustom;
 }
 
 unsigned long long MockDBClientConnection::query(
diff --git a/src/mongo/dbtests/mock/mock_remote_db_server.cpp b/src/mongo/dbtests/mock/mock_remote_db_server.cpp
index e6c766baa24..9c3fe249327 100644
--- a/src/mongo/dbtests/mock/mock_remote_db_server.cpp
+++ b/src/mongo/dbtests/mock/mock_remote_db_server.cpp
@@ -230,7 +230,7 @@ mongo::BSONArray MockRemoteDBServer::query(MockRemoteDBServer::InstanceID id,
 }
 
 mongo::ConnectionString::ConnectionType MockRemoteDBServer::type() const {
-    return mongo::ConnectionString::CUSTOM;
+    return mongo::ConnectionString::ConnectionType::kCustom;
 }
 
 size_t MockRemoteDBServer::getCmdCount() const {
diff --git a/src/mongo/rpc/op_msg_integration_test.cpp b/src/mongo/rpc/op_msg_integration_test.cpp
index 78bbe3d17db..3c3c46ed63b 100644
--- a/src/mongo/rpc/op_msg_integration_test.cpp
+++ b/src/mongo/rpc/op_msg_integration_test.cpp
@@ -196,7 +196,7 @@ TEST(OpMsg, CloseConnectionOnFireAndForgetNotWritablePrimaryError) {
     const auto connStr = unittest::getFixtureConnectionString();
 
     // This test only works against a replica set.
-    if (connStr.type() != ConnectionString::SET) {
+    if (connStr.type() != ConnectionString::ConnectionType::kReplicaSet) {
         return;
     }
 
diff --git a/src/mongo/s/client/shard_registry.cpp b/src/mongo/s/client/shard_registry.cpp
index b19f5d7d77b..4bb4e11a2c0 100644
--- a/src/mongo/s/client/shard_registry.cpp
+++ b/src/mongo/s/client/shard_registry.cpp
@@ -383,8 +383,8 @@ void ShardRegistry::_removeReplicaSet(const std::string& setName) {
 
 void ShardRegistry::updateReplSetHosts(const ConnectionString& givenConnString,
                                        ConnectionStringUpdateType updateType) {
-    invariant(givenConnString.type() == ConnectionString::SET ||
-              givenConnString.type() == ConnectionString::CUSTOM);  // For dbtests
+    invariant(givenConnString.type() == ConnectionString::ConnectionType::kReplicaSet ||
+              givenConnString.type() == ConnectionString::ConnectionType::kCustom);  // For dbtests
 
     auto setName = givenConnString.getSetName();
 
@@ -830,10 +830,10 @@ void ShardRegistryData::_addShard(std::shared_ptr<Shard> shard) {
                 "Adding new shard to shard registry",
                 "shardId"_attr = shard->getId(),
                 "shardConnectionString"_attr = connString);
-    if (connString.type() == ConnectionString::SET) {
+    if (connString.type() == ConnectionString::ConnectionType::kReplicaSet) {
         _rsLookup[connString.getSetName()] = shard;
-    } else if (connString.type() == ConnectionString::CUSTOM) {
-        // CUSTOM connection strings (ie "$dummy:10000) become DBDirectClient connections which
+    } else if (connString.type() == ConnectionString::ConnectionType::kCustom) {
+        // kCustom connection strings (ie "$dummy:10000) become DBDirectClient connections which
         // always return "localhost" as their response to getServerAddress().  This is just for
         // making dbtest work.
         _shardIdLookup[ShardId("localhost")] = shard;
diff --git a/src/mongo/s/client/sharding_connection_hook.cpp b/src/mongo/s/client/sharding_connection_hook.cpp
index 3d153a8012b..0a7374a240e 100644
--- a/src/mongo/s/client/sharding_connection_hook.cpp
+++ b/src/mongo/s/client/sharding_connection_hook.cpp
@@ -49,7 +49,7 @@ ShardingConnectionHook::ShardingConnectionHook(std::unique_ptr<rpc::EgressMetada
     : _egressHook(std::move(egressHook)) {}
 
 void ShardingConnectionHook::onCreate(DBClientBase* conn) {
-    if (conn->type() == ConnectionString::INVALID) {
+    if (conn->type() == ConnectionString::ConnectionType::kInvalid) {
         uasserted(ErrorCodes::BadValue, str::stream() << "Unrecognized connection string.");
     }
 
@@ -72,7 +72,7 @@ void ShardingConnectionHook::onCreate(DBClientBase* conn) {
     });
 
 
-    if (conn->type() == ConnectionString::MASTER) {
+    if (conn->type() == ConnectionString::ConnectionType::kStandalone) {
         BSONObj isMasterResponse;
         if (!conn->runCommand("admin", BSON("ismaster" << 1), isMasterResponse)) {
             uassertStatusOK(getStatusFromCommandResult(isMasterResponse));
diff --git a/src/mongo/s/mongos_main.cpp b/src/mongo/s/mongos_main.cpp
index 4dfdc0414b1..e3475550b8e 100644
--- a/src/mongo/s/mongos_main.cpp
+++ b/src/mongo/s/mongos_main.cpp
@@ -416,8 +416,8 @@ Status initializeSharding(OperationContext* opCtx) {
     };
 
     ShardFactory::BuildersMap buildersMap{
-        {ConnectionString::SET, std::move(setBuilder)},
-        {ConnectionString::MASTER, std::move(masterBuilder)},
+        {ConnectionString::ConnectionType::kReplicaSet, std::move(setBuilder)},
+        {ConnectionString::ConnectionType::kStandalone, std::move(masterBuilder)},
     };
 
     auto shardFactory =
@@ -439,7 +439,7 @@ Status initializeSharding(OperationContext* opCtx) {
             catCache->invalidateEntriesThatReferenceShard(removedShard);
         }};
 
-    if (mongosGlobalParams.configdbs.type() == ConnectionString::INVALID) {
+    if (!mongosGlobalParams.configdbs) {
         return {ErrorCodes::BadValue, "Unrecognized connection string."};
     }
 
diff --git a/src/mongo/s/mongos_options.cpp b/src/mongo/s/mongos_options.cpp
index 4205b63954a..2ab56d4e191 100644
--- a/src/mongo/s/mongos_options.cpp
+++ b/src/mongo/s/mongos_options.cpp
@@ -137,7 +137,8 @@ Status storeMongosOptions(const moe::Environment& params) {
         return configdbConnectionString.getStatus();
     }
 
-    if (configdbConnectionString.getValue().type() != ConnectionString::SET) {
+    if (configdbConnectionString.getValue().type() !=
+        ConnectionString::ConnectionType::kReplicaSet) {
         return Status(ErrorCodes::BadValue,
                       str::stream() << "configdb supports only replica set connection string");
     }
diff --git a/src/mongo/s/query/cluster_find.cpp b/src/mongo/s/query/cluster_find.cpp
index 395f8080acd..cc81dd0df0c 100644
--- a/src/mongo/s/query/cluster_find.cpp
+++ b/src/mongo/s/query/cluster_find.cpp
@@ -196,7 +196,7 @@ std::vector<std::pair<ShardId, BSONObj>> constructRequestsForShards(
     std::vector<std::pair<ShardId, BSONObj>> requests;
     for (const auto& shardId : shardIds) {
         const auto shard = uassertStatusOK(shardRegistry->getShard(opCtx, shardId));
-        invariant(!shard->isConfig() || shard->getConnString().type() != ConnectionString::INVALID);
+        invariant(!shard->isConfig() || shard->getConnString());
 
         BSONObjBuilder cmdBuilder;
         qrToForward->asFindCommand(&cmdBuilder);
diff --git a/src/mongo/s/request_types/add_shard_request_type.cpp b/src/mongo/s/request_types/add_shard_request_type.cpp
index 95ce8b0c8bb..7afaba2874c 100644
--- a/src/mongo/s/request_types/add_shard_request_type.cpp
+++ b/src/mongo/s/request_types/add_shard_request_type.cpp
@@ -88,8 +88,8 @@ StatusWith<AddShardRequest> AddShardRequest::parseInternalFields(const BSONObj&
     }
     ConnectionString connString = std::move(swConnString.getValue());
 
-    if (connString.type() != ConnectionString::MASTER &&
-        connString.type() != ConnectionString::SET) {
+    if (connString.type() != ConnectionString::ConnectionType::kStandalone &&
+        connString.type() != ConnectionString::ConnectionType::kReplicaSet) {
         return {ErrorCodes::FailedToParse,
                 stream() << "Invalid connection string " << connString.toString()};
     }
diff --git a/src/mongo/s/sharding_router_test_fixture.cpp b/src/mongo/s/sharding_router_test_fixture.cpp
index db4a4a3bb29..084a376c59a 100644
--- a/src/mongo/s/sharding_router_test_fixture.cpp
+++ b/src/mongo/s/sharding_router_test_fixture.cpp
@@ -157,8 +157,8 @@ ShardingTestFixture::ShardingTestFixture()
     };
 
     ShardFactory::BuildersMap buildersMap{
-        {ConnectionString::SET, std::move(setBuilder)},
-        {ConnectionString::MASTER, std::move(masterBuilder)},
+        {ConnectionString::ConnectionType::kReplicaSet, std::move(setBuilder)},
+        {ConnectionString::ConnectionType::kStandalone, std::move(masterBuilder)},
     };
 
     auto shardFactory =
diff --git a/src/mongo/scripting/mozjs/mongo.cpp b/src/mongo/scripting/mozjs/mongo.cpp
index 6849e636391..deddb13466d 100644
--- a/src/mongo/scripting/mozjs/mongo.cpp
+++ b/src/mongo/scripting/mozjs/mongo.cpp
@@ -763,7 +763,7 @@ void MongoBase::Functions::isReplicaSetConnection::call(JSContext* cx, JS::CallA
         uasserted(ErrorCodes::BadValue, "isReplicaSetConnection takes no args");
     }
 
-    args.rval().setBoolean(conn->type() == ConnectionString::ConnectionType::SET);
+    args.rval().setBoolean(conn->type() == ConnectionString::ConnectionType::kReplicaSet);
 }
 
 void MongoBase::Functions::_markNodeAsFailed::call(JSContext* cx, JS::CallArgs args) {