SERVER-22320 remove SYNC option and SyncClusterConnection

26 files changed, 119 insertions, 1612 deletions

diff --git a/src/mongo/client/SConscript b/src/mongo/client/SConscript
index 7aeab208ca4..71a65c735a2 100644
--- a/src/mongo/client/SConscript
+++ b/src/mongo/client/SConscript
@@ -131,7 +131,6 @@ env.Library(
         'global_conn_pool.cpp',
         'replica_set_monitor.cpp',
         'replica_set_monitor_manager.cpp',
-        'syncclusterconnection.cpp',
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/db/auth/authcommon',
diff --git a/src/mongo/client/connection_string.cpp b/src/mongo/client/connection_string.cpp
index 69b3f952039..18ee8ea1234 100644
--- a/src/mongo/client/connection_string.cpp
+++ b/src/mongo/client/connection_string.cpp
@@ -47,6 +47,7 @@ ConnectionString::ConnectionString(StringData setName, std::vector<HostAndPort>
     _finishInit();
 }
 
+// TODO: unify c-tors
 ConnectionString::ConnectionString(ConnectionType type,
                                    const std::string& s,
                                    const std::string& setName) {
@@ -63,18 +64,9 @@ ConnectionString::ConnectionString(ConnectionType type,
     _finishInit();
 }
 
-ConnectionString::ConnectionString(const std::string& s, ConnectionType favoredMultipleType) {
+ConnectionString::ConnectionString(const std::string& s, ConnectionType connType)
+    : _type(connType) {
     _fillServers(s);
-
-    if (_type != INVALID) {
-        // set already
-    } else if (_servers.size() == 1) {
-        _type = MASTER;
-    } else {
-        _type = favoredMultipleType;
-        verify(_type == SET || _type == SYNC);
-    }
-
     _finishInit();
 }
 
@@ -83,6 +75,7 @@ ConnectionString ConnectionString::forReplicaSet(StringData setName,
     return ConnectionString(setName, std::move(servers));
 }
 
+// TODO: rewrite parsing  make it more reliable
 void ConnectionString::_fillServers(std::string s) {
     //
     // Custom-handled servers/replica sets start with '$'
@@ -90,34 +83,38 @@ void ConnectionString::_fillServers(std::string s) {
     // (also disallows $replicaSetName hosts)
     //
 
-    if (s.find('$') == 0)
+    if (s.find('$') == 0) {
         _type = CUSTOM;
+    }
 
-    {
-        std::string::size_type idx = s.find('/');
-        if (idx != std::string::npos) {
-            _setName = s.substr(0, idx);
-            s = s.substr(idx + 1);
-            if (_type != CUSTOM)
-                _type = SET;
-        }
+    std::string::size_type idx = s.find('/');
+    if (idx != std::string::npos) {
+        _setName = s.substr(0, idx);
+        s = s.substr(idx + 1);
+        if (_type != CUSTOM)
+            _type = SET;
     }
 
-    std::string::size_type idx;
     while ((idx = s.find(',')) != std::string::npos) {
         _servers.push_back(HostAndPort(s.substr(0, idx)));
         s = s.substr(idx + 1);
     }
+
     _servers.push_back(HostAndPort(s));
+
+    if (_servers.size() == 1 && _type == INVALID) {
+        _type = MASTER;
+    }
 }
 
 void ConnectionString::_finishInit() {
     switch (_type) {
         case MASTER:
+            verify(_setName.empty());
             verify(_servers.size() == 1);
             break;
         case SET:
-            verify(_setName.size());
+            verify(!_setName.empty());
             verify(_servers.size() >= 1);  // 1 is ok since we can derive
             break;
         default:
@@ -149,6 +146,7 @@ void ConnectionString::_finishInit() {
     _string = ss.str();
 }
 
+// TODO: SERVER-23014
 bool ConnectionString::sameLogicalEndpoint(const ConnectionString& other) const {
     if (_type != other._type) {
         return false;
@@ -161,26 +159,6 @@ bool ConnectionString::sameLogicalEndpoint(const ConnectionString& other) const
             return _servers[0] == other._servers[0];
         case SET:
             return _setName == other._setName;
-        case SYNC:
-            // The servers all have to be the same in each, but not in the same order.
-            if (_servers.size() != other._servers.size()) {
-                return false;
-            }
-
-            for (unsigned i = 0; i < _servers.size(); i++) {
-                bool found = false;
-                for (unsigned j = 0; j < other._servers.size(); j++) {
-                    if (_servers[i] == other._servers[j]) {
-                        found = true;
-                        break;
-                    }
-                }
-
-                if (!found)
-                    return false;
-            }
-
-            return true;
         case CUSTOM:
             return _string == other._string;
     }
@@ -209,9 +187,11 @@ StatusWith<ConnectionString> ConnectionString::parse(const std::string& url) {
         return ConnectionString(singleHost);
     }
 
-    // Sharding config server
     if (numCommas == 2) {
-        return ConnectionString(SYNC, url, "");
+        return Status(ErrorCodes::FailedToParse,
+                      str::stream() << "mirrored config server connections are not supported; for "
+                                       "config server replica sets be sure to use the replica set "
+                                       "connection string");
     }
 
     return Status(ErrorCodes::FailedToParse, str::stream() << "invalid url [" << url << "]");
@@ -225,8 +205,6 @@ std::string ConnectionString::typeToString(ConnectionType type) {
             return "master";
         case SET:
             return "set";
-        case SYNC:
-            return "sync";
         case CUSTOM:
             return "custom";
     }
diff --git a/src/mongo/client/connection_string.h b/src/mongo/client/connection_string.h
index 83e20906ed3..fbb29a829f6 100644
--- a/src/mongo/client/connection_string.h
+++ b/src/mongo/client/connection_string.h
@@ -47,10 +47,6 @@ class DBClientBase;
  *    server
  *    server:port
  *    foo/server:port,server:port   SET
- *    server,server,server          SYNC
- *                                    Warning - you usually don't want "SYNC", it's used
- *                                    for some special things such as sharding config servers.
- *                                    See syncclusterconnection.h for more info.
  *
  * Typical use:
  *
@@ -60,7 +56,7 @@ class DBClientBase;
  */
 class ConnectionString {
 public:
-    enum ConnectionType { INVALID, MASTER, SET, SYNC, CUSTOM };
+    enum ConnectionType { INVALID, MASTER, SET, CUSTOM };
 
     ConnectionString() = default;
 
@@ -86,7 +82,7 @@ public:
                      std::vector<HostAndPort> servers,
                      const std::string& setName);
 
-    ConnectionString(const std::string& s, ConnectionType favoredMultipleType);
+    ConnectionString(const std::string& s, ConnectionType connType);
 
     bool isValid() const {
         return _type != INVALID;
diff --git a/src/mongo/client/connection_string_connect.cpp b/src/mongo/client/connection_string_connect.cpp
index efca34792e6..3a8e0287656 100644
--- a/src/mongo/client/connection_string_connect.cpp
+++ b/src/mongo/client/connection_string_connect.cpp
@@ -36,7 +36,6 @@
 
 #include "mongo/client/dbclient_rs.h"
 #include "mongo/client/dbclientinterface.h"
-#include "mongo/client/syncclusterconnection.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/log.h"
@@ -69,15 +68,6 @@ DBClientBase* ConnectionString::connect(std::string& errmsg, double socketTimeou
             return set.release();
         }
 
-        case SYNC: {
-            // TODO , don't copy
-            std::list<HostAndPort> l;
-            for (unsigned i = 0; i < _servers.size(); i++)
-                l.push_back(_servers[i]);
-            SyncClusterConnection* c = new SyncClusterConnection(l, socketTimeout);
-            return c;
-        }
-
         case CUSTOM: {
             // Lock in case other things are modifying this at the same time
             stdx::lock_guard<stdx::mutex> lk(_connectHookMutex);
diff --git a/src/mongo/client/connection_string_test.cpp b/src/mongo/client/connection_string_test.cpp
index 4a1dfd81384..655ff17c207 100644
--- a/src/mongo/client/connection_string_test.cpp
+++ b/src/mongo/client/connection_string_test.cpp
@@ -35,7 +35,8 @@
 namespace {
 
 using namespace mongo;
-
+/*
+   TODO: SERVER-23014 SYNC is gone but this can be a good check for equality
 TEST(ConnectionString, EqualitySync) {
     ConnectionString cs(ConnectionString::SYNC, "a,b,c", "");
 
@@ -45,5 +46,5 @@ TEST(ConnectionString, EqualitySync) {
 
     ASSERT(!cs.sameLogicalEndpoint(ConnectionString(ConnectionString::SYNC, "d,a,b", "")));
 }
-
+*/
 }  // namespace
diff --git a/src/mongo/client/connpool.cpp b/src/mongo/client/connpool.cpp
index 2a019db9787..4bdc263cf33 100644
--- a/src/mongo/client/connpool.cpp
+++ b/src/mongo/client/connpool.cpp
@@ -41,7 +41,6 @@
 #include "mongo/client/connection_string.h"
 #include "mongo/client/global_conn_pool.h"
 #include "mongo/client/replica_set_monitor.h"
-#include "mongo/client/syncclusterconnection.h"
 #include "mongo/executor/connection_pool_stats.h"
 #include "mongo/util/exit.h"
 #include "mongo/util/log.h"
@@ -474,10 +473,9 @@ void ScopedDbConnection::done() {
 void ScopedDbConnection::_setSocketTimeout() {
     if (!_conn)
         return;
+
     if (_conn->type() == ConnectionString::MASTER)
-        ((DBClientConnection*)_conn)->setSoTimeout(_socketTimeout);
-    else if (_conn->type() == ConnectionString::SYNC)
-        ((SyncClusterConnection*)_conn)->setAllSoTimeouts(_socketTimeout);
+        static_cast<DBClientConnection*>(_conn)->setSoTimeout(_socketTimeout);
 }
 
 ScopedDbConnection::~ScopedDbConnection() {
diff --git a/src/mongo/client/dbclientcursor.cpp b/src/mongo/client/dbclientcursor.cpp
index 2e0a5bdade3..489f647a2ca 100644
--- a/src/mongo/client/dbclientcursor.cpp
+++ b/src/mongo/client/dbclientcursor.cpp
@@ -432,8 +432,7 @@ void DBClientCursor::attach(AScopedConnection* conn) {
     verify(conn);
     verify(conn->get());
 
-    if (conn->get()->type() == ConnectionString::SET ||
-        conn->get()->type() == ConnectionString::SYNC) {
+    if (conn->get()->type() == ConnectionString::SET) {
         if (_lazyHost.size() > 0)
             _scopedHost = _lazyHost;
         else if (_client)
diff --git a/src/mongo/client/remote_command_targeter_factory_impl.cpp b/src/mongo/client/remote_command_targeter_factory_impl.cpp
index 338cde7c504..3c3b1974eac 100644
--- a/src/mongo/client/remote_command_targeter_factory_impl.cpp
+++ b/src/mongo/client/remote_command_targeter_factory_impl.cpp
@@ -54,7 +54,6 @@ std::unique_ptr<RemoteCommandTargeter> RemoteCommandTargeterFactoryImpl::create(
             return stdx::make_unique<RemoteCommandTargeterRS>(connStr.getSetName(),
                                                               connStr.getServers());
         case ConnectionString::INVALID:
-        case ConnectionString::SYNC:
             // These connections should never be seen
             break;
     }
diff --git a/src/mongo/client/syncclusterconnection.cpp b/src/mongo/client/syncclusterconnection.cpp
deleted file mode 100644
index 52ed06592ec..00000000000
--- a/src/mongo/client/syncclusterconnection.cpp
+++ /dev/null
@@ -1,689 +0,0 @@
-// syncclusterconnection.cpp
-/*
- *    Copyright 2010 10gen Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects
- *    for all of the code used other than as permitted herein. If you modify
- *    file(s) with this exception, you may extend this exception to your
- *    version of the file(s), but you are not obligated to do so. If you do not
- *    wish to do so, delete this exception statement from your version. If you
- *    delete this exception statement from all source files in the program,
- *    then also delete it in the license file.
- */
-
-
-#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kNetwork
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/client/syncclusterconnection.h"
-
-#include "mongo/client/dbclientcursor.h"
-#include "mongo/client/dbclientinterface.h"
-#include "mongo/db/dbmessage.h"
-#include "mongo/db/namespace_string.h"
-#include "mongo/rpc/get_status_from_command_result.h"
-#include "mongo/util/log.h"
-
-namespace mongo {
-
-using std::unique_ptr;
-using std::endl;
-using std::list;
-using std::map;
-using std::string;
-using std::stringstream;
-using std::vector;
-
-namespace {
-SyncClusterConnection::ConnectionValidationHook connectionHook;
-}  // namespace
-
-SyncClusterConnection::SyncClusterConnection(const list<HostAndPort>& L, double socketTimeout)
-    : _socketTimeout(socketTimeout) {
-    {
-        stringstream s;
-        int n = 0;
-        for (list<HostAndPort>::const_iterator i = L.begin(); i != L.end(); i++) {
-            if (++n > 1)
-                s << ',';
-            s << i->toString();
-        }
-        _address = s.str();
-    }
-    for (list<HostAndPort>::const_iterator i = L.begin(); i != L.end(); i++)
-        _connect(i->toString());
-}
-
-SyncClusterConnection::SyncClusterConnection(string commaSeparated, double socketTimeout)
-    : _socketTimeout(socketTimeout) {
-    _address = commaSeparated;
-    string::size_type idx;
-    while ((idx = commaSeparated.find(',')) != string::npos) {
-        string h = commaSeparated.substr(0, idx);
-        commaSeparated = commaSeparated.substr(idx + 1);
-        _connect(h);
-    }
-    _connect(commaSeparated);
-    uassert(8004, "SyncClusterConnection needs 3 servers", _conns.size() == 3);
-}
-
-SyncClusterConnection::SyncClusterConnection(const std::string& a,
-                                             const std::string& b,
-                                             const std::string& c,
-                                             double socketTimeout)
-    : _socketTimeout(socketTimeout) {
-    _address = a + "," + b + "," + c;
-    // connect to all even if not working
-    _connect(a);
-    _connect(b);
-    _connect(c);
-}
-
-SyncClusterConnection::SyncClusterConnection(SyncClusterConnection& prev, double socketTimeout)
-    : _socketTimeout(socketTimeout) {
-    verify(0);
-}
-
-SyncClusterConnection::~SyncClusterConnection() {
-    for (size_t i = 0; i < _conns.size(); i++)
-        delete _conns[i];
-    _conns.clear();
-}
-
-void SyncClusterConnection::setConnectionValidationHook(ConnectionValidationHook hook) {
-    connectionHook = std::move(hook);
-}
-
-bool SyncClusterConnection::prepare(string& errmsg) {
-    _lastErrors.clear();
-
-    bool ok = true;
-    errmsg = "";
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        string singleErr;
-        try {
-            _conns[i]->simpleCommand("admin", NULL, "resetError");
-            singleErr = _conns[i]->getLastError(true);
-
-            if (singleErr.size() == 0)
-                continue;
-
-        } catch (const DBException& e) {
-            if (e.getCode() == ErrorCodes::IncompatibleCatalogManager) {
-                throw;
-            }
-            singleErr = e.toString();
-        }
-        ok = false;
-        errmsg += " " + _conns[i]->toString() + ":" + singleErr;
-    }
-
-    return ok;
-}
-
-void SyncClusterConnection::_checkLast() {
-    _lastErrors.clear();
-    vector<string> errors;
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        BSONObj res;
-        string err;
-        try {
-            if (!_conns[i]->runCommand("admin", BSON("getlasterror" << 1 << "fsync" << 1), res))
-                err = "cmd failed: ";
-        } catch (std::exception& e) {
-            err += e.what();
-        } catch (...) {
-            err += "unknown failure";
-        }
-        _lastErrors.push_back(res.getOwned());
-        errors.push_back(err);
-    }
-
-    verify(_lastErrors.size() == errors.size() && _lastErrors.size() == _conns.size());
-
-    stringstream err;
-    bool ok = true;
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        BSONObj res = _lastErrors[i];
-        if (res["ok"].trueValue() &&
-            (res["fsyncFiles"].numberInt() > 0 || res.hasElement("waited") ||
-             res["syncMillis"].numberInt() >= 0))
-            continue;
-        ok = false;
-        err << _conns[i]->toString() << ": " << res << " " << errors[i];
-    }
-
-    if (ok)
-        return;
-    throw UserException(8001, (string) "SyncClusterConnection write op failed: " + err.str());
-}
-
-BSONObj SyncClusterConnection::getLastErrorDetailed(bool fsync, bool j, int w, int wtimeout) {
-    return getLastErrorDetailed("admin", fsync, j, w, wtimeout);
-}
-
-BSONObj SyncClusterConnection::getLastErrorDetailed(
-    const std::string& db, bool fsync, bool j, int w, int wtimeout) {
-    if (_lastErrors.size())
-        return _lastErrors[0];
-    return DBClientBase::getLastErrorDetailed(db, fsync, j, w, wtimeout);
-}
-
-void SyncClusterConnection::_connect(const std::string& hostStr) {
-    log() << "SyncClusterConnection connecting to [" << hostStr << "]" << endl;
-    const HostAndPort host(hostStr);
-    DBClientConnection* c;
-    if (connectionHook) {
-        c = new DBClientConnection(
-            true,  // auto reconnect
-            0,     // socket timeout
-            [this, host](const executor::RemoteCommandResponse& isMasterReply) {
-                return connectionHook(host, isMasterReply);
-            });
-    } else {
-        c = new DBClientConnection(true);
-    }
-
-    c->setRequestMetadataWriter(getRequestMetadataWriter());
-    c->setReplyMetadataReader(getReplyMetadataReader());
-    c->setSoTimeout(_socketTimeout);
-    Status status = c->connect(host);
-    if (!status.isOK()) {
-        log() << "SyncClusterConnection connect fail to: " << hostStr << causedBy(status);
-        if (status == ErrorCodes::IncompatibleCatalogManager) {
-            // Make sure to propagate IncompatibleCatalogManager errors to trigger catalog manager
-            // swapping.
-            uassertStatusOK(status);
-        }
-    }
-    _connAddresses.push_back(hostStr);
-    _conns.push_back(c);
-}
-
-bool SyncClusterConnection::runCommand(const std::string& dbname,
-                                       const BSONObj& cmd,
-                                       BSONObj& info,
-                                       int options) {
-    std::string ns = dbname + ".$cmd";
-    BSONObj interposedCmd = cmd;
-
-    if (getRequestMetadataWriter()) {
-        // We have a metadata writer. We need to upconvert the metadata, write to it,
-        // Then downconvert it again. This unfortunate, but this code is going to be
-        // removed anyway as part of CSRS.
-
-        BSONObj upconvertedCommand;
-        BSONObj upconvertedMetadata;
-
-        std::tie(upconvertedCommand, upconvertedMetadata) =
-            uassertStatusOK(rpc::upconvertRequestMetadata(cmd, options));
-
-        BSONObjBuilder metadataBob;
-        metadataBob.appendElements(upconvertedMetadata);
-
-        uassertStatusOK(getRequestMetadataWriter()(&metadataBob, getServerAddress()));
-
-        std::tie(interposedCmd, options) = uassertStatusOK(
-            rpc::downconvertRequestMetadata(std::move(upconvertedCommand), metadataBob.done()));
-    }
-
-    BSONObj legacyResult = findOne(ns, Query(interposedCmd), 0, options);
-
-    BSONObj upconvertedMetadata;
-    BSONObj upconvertedReply;
-
-    std::tie(upconvertedReply, upconvertedMetadata) =
-        uassertStatusOK(rpc::upconvertReplyMetadata(legacyResult));
-
-    if (getReplyMetadataReader()) {
-        // TODO: what does getServerAddress() actually mean here as this connection
-        // represents a connection to 1 or 3 config servers...
-        uassertStatusOK(getReplyMetadataReader()(upconvertedReply, getServerAddress()));
-    }
-
-    info = upconvertedReply;
-
-    return isOk(info);
-}
-
-BSONObj SyncClusterConnection::findOne(const string& ns,
-                                       const Query& query,
-                                       const BSONObj* fieldsToReturn,
-                                       int queryOptions) {
-    if (ns.find(".$cmd") != string::npos) {
-        string cmdName = query.obj.firstElementFieldName();
-
-        int lockType = _lockType(cmdName);
-
-        if (lockType > 0) {  // write $cmd
-            string errmsg;
-            if (!prepare(errmsg))
-                throw UserException(ErrorCodes::PrepareConfigsFailed,
-                                    (string) "SyncClusterConnection::findOne prepare failed: " +
-                                        errmsg);
-
-            vector<BSONObj> all;
-            for (size_t i = 0; i < _conns.size(); i++) {
-                all.push_back(_conns[i]->findOne(ns, query, 0, queryOptions).getOwned());
-            }
-
-            _checkLast();
-
-            for (size_t i = 0; i < all.size(); i++) {
-                Status status = getStatusFromCommandResult(all[i]);
-                if (status.isOK()) {
-                    continue;
-                }
-
-                stringstream ss;
-                ss << "write $cmd failed on a node: " << status.toString();
-                ss << " " << _conns[i]->toString();
-                ss << " ns: " << ns;
-                ss << " cmd: " << query.toString();
-                throw UserException(status.code(), ss.str());
-            }
-
-            return all[0];
-        }
-    }
-
-    return DBClientBase::findOne(ns, query, fieldsToReturn, queryOptions);
-}
-
-void SyncClusterConnection::_auth(const BSONObj& params) {
-    // A SCC is authenticated if any connection has been authenticated
-    // Credentials are stored in the auto-reconnect connections.
-
-    bool authedOnce = false;
-    vector<string> errors;
-
-    for (vector<DBClientConnection*>::iterator it = _conns.begin(); it < _conns.end(); ++it) {
-        massert(15848, "sync cluster of sync clusters?", (*it)->type() != ConnectionString::SYNC);
-
-        // Authenticate or collect the error message
-        string lastErrmsg;
-        bool authed;
-        try {
-            // Auth errors can manifest either as exceptions or as false results
-            // TODO: Make this better
-            (*it)->auth(params);
-            authed = true;
-        } catch (const DBException& e) {
-            // auth will be retried on reconnect
-            lastErrmsg = e.what();
-            authed = false;
-        }
-
-        if (!authed) {
-            // Since we're using auto-reconnect connections, we're sure the auth info has been
-            // stored if needed for later
-
-            lastErrmsg = str::stream() << "auth error on " << (*it)->getServerAddress()
-                                       << causedBy(lastErrmsg);
-
-            LOG(1) << lastErrmsg << endl;
-            errors.push_back(lastErrmsg);
-        }
-
-        authedOnce = authedOnce || authed;
-    }
-
-    if (authedOnce)
-        return;
-
-    // Assemble the error message
-    str::stream errStream;
-    for (vector<string>::iterator it = errors.begin(); it != errors.end(); ++it) {
-        if (it != errors.begin())
-            errStream << " ::and:: ";
-        errStream << *it;
-    }
-
-    uasserted(ErrorCodes::AuthenticationFailed, errStream);
-}
-
-// TODO: logout is required for use of this class outside of a cluster environment
-
-unique_ptr<DBClientCursor> SyncClusterConnection::query(const string& ns,
-                                                        Query query,
-                                                        int nToReturn,
-                                                        int nToSkip,
-                                                        const BSONObj* fieldsToReturn,
-                                                        int queryOptions,
-                                                        int batchSize) {
-    _lastErrors.clear();
-    if (ns.find(".$cmd") != string::npos) {
-        string cmdName = query.obj.firstElementFieldName();
-        int lockType = _lockType(cmdName);
-        uassert(13054,
-                (string) "write $cmd not supported in SyncClusterConnection::query for:" + cmdName,
-                lockType <= 0);
-    }
-
-    return _queryOnActive(ns, query, nToReturn, nToSkip, fieldsToReturn, queryOptions, batchSize);
-}
-
-bool SyncClusterConnection::_commandOnActive(const string& dbname,
-                                             const BSONObj& cmd,
-                                             BSONObj& info,
-                                             int options) {
-    unique_ptr<DBClientCursor> cursor = _queryOnActive(dbname + ".$cmd", cmd, 1, 0, 0, options, 0);
-    if (cursor->more())
-        info = cursor->next().copy();
-    else
-        info = BSONObj();
-    return isOk(info);
-}
-
-void SyncClusterConnection::attachQueryHandler(QueryHandler* handler) {
-    _customQueryHandler.reset(handler);
-}
-
-unique_ptr<DBClientCursor> SyncClusterConnection::_queryOnActive(const string& ns,
-                                                                 Query query,
-                                                                 int nToReturn,
-                                                                 int nToSkip,
-                                                                 const BSONObj* fieldsToReturn,
-                                                                 int queryOptions,
-                                                                 int batchSize) {
-    if (_customQueryHandler && _customQueryHandler->canHandleQuery(ns, query)) {
-        LOG(2) << "custom query handler used for query on " << ns << ": " << query.toString()
-               << endl;
-
-        return _customQueryHandler->handleQuery(
-            _connAddresses, ns, query, nToReturn, nToSkip, fieldsToReturn, queryOptions, batchSize);
-    }
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        try {
-            unique_ptr<DBClientCursor> cursor = _conns[i]->query(
-                ns, query, nToReturn, nToSkip, fieldsToReturn, queryOptions, batchSize);
-            if (cursor.get())
-                return cursor;
-
-            log() << "query on " << ns << ": " << query.toString()
-                  << " failed to: " << _conns[i]->toString() << " no data" << endl;
-        } catch (std::exception& e) {
-            log() << "query on " << ns << ": " << query.toString()
-                  << " failed to: " << _conns[i]->toString() << " exception: " << e.what() << endl;
-        } catch (...) {
-            log() << "query on " << ns << ": " << query.toString()
-                  << " failed to: " << _conns[i]->toString() << " exception" << endl;
-        }
-    }
-    throw UserException(ErrorCodes::HostUnreachable,
-                        str::stream()
-                            << "all servers down/unreachable when querying: " << _address);
-}
-
-unique_ptr<DBClientCursor> SyncClusterConnection::getMore(const string& ns,
-                                                          long long cursorId,
-                                                          int nToReturn,
-                                                          int options) {
-    uassert(10022, "SyncClusterConnection::getMore not supported yet", 0);
-    unique_ptr<DBClientCursor> c;
-    return c;
-}
-
-void SyncClusterConnection::insert(const string& ns, BSONObj obj, int flags) {
-    uassert(13119,
-            str::stream() << "SyncClusterConnection::insert obj has to have an _id: " << obj,
-            nsToCollectionSubstring(ns) == "system.indexes" || obj["_id"].type());
-
-    string errmsg;
-    if (!prepare(errmsg))
-        throw UserException(8003,
-                            (string) "SyncClusterConnection::insert prepare failed: " + errmsg);
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        _conns[i]->insert(ns, obj, flags);
-    }
-
-    _checkLast();
-}
-
-void SyncClusterConnection::insert(const string& ns, const vector<BSONObj>& v, int flags) {
-    if (v.size() == 1) {
-        insert(ns, v[0], flags);
-        return;
-    }
-
-    for (vector<BSONObj>::const_iterator it = v.begin(); it != v.end(); ++it) {
-        BSONObj obj = *it;
-        if (obj["_id"].type() == EOO) {
-            string assertMsg = "SyncClusterConnection::insert (batched) obj misses an _id: ";
-            uasserted(16743, assertMsg + obj.jsonString());
-        }
-    }
-
-    // fsync all connections before starting the batch.
-    string errmsg;
-    if (!prepare(errmsg)) {
-        string assertMsg = "SyncClusterConnection::insert (batched) prepare failed: ";
-        throw UserException(16744, assertMsg + errmsg);
-    }
-
-    // We still want one getlasterror per document, even if they're batched.
-    for (size_t i = 0; i < _conns.size(); i++) {
-        for (vector<BSONObj>::const_iterator it = v.begin(); it != v.end(); ++it) {
-            _conns[i]->insert(ns, *it, flags);
-            _conns[i]->getLastErrorDetailed();
-        }
-    }
-
-    // We issue a final getlasterror, but this time with an fsync.
-    _checkLast();
-}
-
-void SyncClusterConnection::remove(const string& ns, Query query, int flags) {
-    string errmsg;
-    if (!prepare(errmsg))
-        throw UserException(8020,
-                            (string) "SyncClusterConnection::remove prepare failed: " + errmsg);
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        _conns[i]->remove(ns, query, flags);
-    }
-
-    _checkLast();
-}
-
-void SyncClusterConnection::update(const string& ns, Query query, BSONObj obj, int flags) {
-    if (flags & UpdateOption_Upsert) {
-        uassert(
-            13120, "SyncClusterConnection::update upsert query needs _id", query.obj["_id"].type());
-    }
-
-    string errmsg;
-    if (!prepare(errmsg)) {
-        throw UserException(
-            8005, str::stream() << "SyncClusterConnection::update prepare failed: " << errmsg);
-    }
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        _conns[i]->update(ns, query, obj, flags);
-    }
-
-    _checkLast();
-    invariant(_lastErrors.size() > 1);
-
-    const int a = _lastErrors[0]["n"].numberInt();
-
-    for (unsigned i = 1; i < _lastErrors.size(); i++) {
-        int b = _lastErrors[i]["n"].numberInt();
-
-        if (a == b)
-            continue;
-
-        throw UpdateNotTheSame(8017,
-                               str::stream() << "update not consistent "
-                                             << " ns: " << ns << " query: " << query.toString()
-                                             << " update: " << obj << " gle1: " << _lastErrors[0]
-                                             << " gle2: " << _lastErrors[i],
-                               _connAddresses,
-                               _lastErrors);
-    }
-}
-
-string SyncClusterConnection::_toString() const {
-    stringstream ss;
-    ss << "SyncClusterConnection ";
-    ss << " [";
-    for (size_t i = 0; i < _conns.size(); i++) {
-        if (i != 0)
-            ss << ",";
-        if (_conns[i]) {
-            ss << _conns[i]->toString();
-        } else {
-            ss << "(no conn)";
-        }
-    }
-    ss << "]";
-    return ss.str();
-}
-
-bool SyncClusterConnection::call(Message& toSend,
-                                 Message& response,
-                                 bool assertOk,
-                                 string* actualServer) {
-    uassert(8006,
-            "SyncClusterConnection::call can only be used directly for dbQuery",
-            toSend.operation() == dbQuery);
-
-    DbMessage d(toSend);
-    uassert(8007, "SyncClusterConnection::call can't handle $cmd", strstr(d.getns(), "$cmd") == 0);
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        try {
-            bool ok = _conns[i]->call(toSend, response, assertOk, nullptr);
-            if (ok) {
-                if (actualServer)
-                    *actualServer = _connAddresses[i];
-                return ok;
-            }
-            log() << "call failed to: " << _conns[i]->toString() << " no data" << endl;
-        } catch (...) {
-            log() << "call failed to: " << _conns[i]->toString() << " exception" << endl;
-        }
-    }
-    throw UserException(8008, str::stream() << "all servers down/unreachable: " << _address);
-}
-
-void SyncClusterConnection::say(Message& toSend, bool isRetry, string* actualServer) {
-    string errmsg;
-    if (!prepare(errmsg))
-        throw UserException(13397, (string) "SyncClusterConnection::say prepare failed: " + errmsg);
-
-    for (size_t i = 0; i < _conns.size(); i++) {
-        _conns[i]->say(toSend);
-    }
-
-    // TODO: should we set actualServer??
-
-    _checkLast();
-}
-
-int SyncClusterConnection::_lockType(const string& name) {
-    {
-        stdx::lock_guard<stdx::mutex> lk(_mutex);
-        map<string, int>::iterator i = _lockTypes.find(name);
-        if (i != _lockTypes.end())
-            return i->second;
-    }
-
-    BSONObj info;
-    uassert(13053,
-            str::stream() << "help failed: " << info,
-            _commandOnActive("admin",
-                             BSON(name << "1"
-                                       << "help" << 1),
-                             info));
-
-    int lockType = info["lockType"].numberInt();
-
-    stdx::lock_guard<stdx::mutex> lk(_mutex);
-    _lockTypes[name] = lockType;
-    return lockType;
-}
-
-void SyncClusterConnection::killCursor(long long cursorID) {
-    // should never need to do this
-    verify(0);
-}
-
-// A SCC should be reused only if all the existing connections haven't been broken in the
-// background.
-// Note: an SCC may have missing connections if a config server is temporarily offline,
-// but reading from the others is still allowed.
-bool SyncClusterConnection::isStillConnected() {
-    for (size_t i = 0; i < _conns.size(); i++) {
-        if (_conns[i] && !_conns[i]->isStillConnected())
-            return false;
-    }
-    return true;
-}
-
-int SyncClusterConnection::getMinWireVersion() {
-    int minVersion = 0;
-    for (const auto& host : _conns) {
-        minVersion = std::max(minVersion, host->getMinWireVersion());
-    }
-    return minVersion;
-}
-
-int SyncClusterConnection::getMaxWireVersion() {
-    int maxVersion = std::numeric_limits<int>::max();
-    for (const auto& host : _conns) {
-        maxVersion = std::min(maxVersion, host->getMaxWireVersion());
-    }
-    return maxVersion;
-}
-
-void SyncClusterConnection::setAllSoTimeouts(double socketTimeout) {
-    _socketTimeout = socketTimeout;
-    for (size_t i = 0; i < _conns.size(); i++)
-
-        if (_conns[i])
-            _conns[i]->setSoTimeout(socketTimeout);
-}
-
-void SyncClusterConnection::setRequestMetadataWriter(rpc::RequestMetadataWriter writer) {
-    // Set the hooks in both our sub-connections and in ourselves.
-    for (size_t i = 0; i < _conns.size(); ++i) {
-        if (_conns[i]) {
-            _conns[i]->setRequestMetadataWriter(writer);
-        }
-    }
-    DBClientWithCommands::setRequestMetadataWriter(std::move(writer));
-}
-
-void SyncClusterConnection::setReplyMetadataReader(rpc::ReplyMetadataReader reader) {
-    // Set the hooks in both our sub-connections and in ourselves.
-    for (size_t i = 0; i < _conns.size(); ++i) {
-        if (_conns[i]) {
-            _conns[i]->setReplyMetadataReader(reader);
-        }
-    }
-    DBClientWithCommands::setReplyMetadataReader(std::move(reader));
-}
-}
diff --git a/src/mongo/client/syncclusterconnection.h b/src/mongo/client/syncclusterconnection.h
deleted file mode 100644
index 40373d4ae19..00000000000
--- a/src/mongo/client/syncclusterconnection.h
+++ /dev/null
@@ -1,272 +0,0 @@
-// @file syncclusterconnection.h
-
-/*
- *    Copyright 2010 10gen Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects
- *    for all of the code used other than as permitted herein. If you modify
- *    file(s) with this exception, you may extend this exception to your
- *    version of the file(s), but you are not obligated to do so. If you do not
- *    wish to do so, delete this exception statement from your version. If you
- *    delete this exception statement from all source files in the program,
- *    then also delete it in the license file.
- */
-
-#pragma once
-
-
-#include "mongo/bson/bsonelement.h"
-#include "mongo/bson/bsonobj.h"
-#include "mongo/client/dbclientinterface.h"
-#include "mongo/stdx/mutex.h"
-#include "mongo/stdx/functional.h"
-#include "mongo/util/concurrency/mutex.h"
-
-namespace mongo {
-
-/**
- * This is a connection to a cluster of servers that operate as one
- * for super high durability.
- *
- * Write operations are two-phase.  First, all nodes are asked to fsync. If successful
- * everywhere, the write is sent everywhere and then followed by an fsync.  There is no
- * rollback if a problem occurs during the second phase.  Naturally, with all these fsyncs,
- * these operations will be quite slow -- use sparingly.
- *
- * Read operations are sent to a single random node.
- *
- * The class checks if a command is read or write style, and sends to a single
- * node if a read lock command and to all in two phases with a write style command.
- */
-class SyncClusterConnection : public DBClientBase {
-public:
-    using DBClientBase::query;
-    using DBClientBase::update;
-    using DBClientBase::remove;
-
-    class QueryHandler;
-
-    /**
-     * Hook run on the response of an isMaster request.  Run on the DBClientConnections that
-     * SyncClusterConnection uses under the hood.  Used to detect and signal when the catalog
-     * manager needs swapping.
-     */
-    using ConnectionValidationHook = stdx::function<Status(
-        const HostAndPort& host, const executor::RemoteCommandResponse& isMasterReply)>;
-
-
-    /**
-     * @param commaSeparated should be 3 hosts comma separated
-     */
-    SyncClusterConnection(const std::list<HostAndPort>&, double socketTimeout = 0);
-    SyncClusterConnection(std::string commaSeparated, double socketTimeout = 0);
-    SyncClusterConnection(const std::string& a,
-                          const std::string& b,
-                          const std::string& c,
-                          double socketTimeout = 0);
-    ~SyncClusterConnection();
-
-    /**
-     * Sets the ConnectionValidationHook that will be used for the DBClientConnections created by
-     * all future constructed SyncClusterConnections.
-     */
-    static void setConnectionValidationHook(ConnectionValidationHook hook);
-
-    /**
-     * @return true if all servers are up and ready for writes
-     */
-    bool prepare(std::string& errmsg);
-
-    // --- from DBClientInterface
-
-    virtual BSONObj findOne(const std::string& ns,
-                            const Query& query,
-                            const BSONObj* fieldsToReturn,
-                            int queryOptions);
-
-    virtual std::unique_ptr<DBClientCursor> query(const std::string& ns,
-                                                  Query query,
-                                                  int nToReturn,
-                                                  int nToSkip,
-                                                  const BSONObj* fieldsToReturn,
-                                                  int queryOptions,
-                                                  int batchSize);
-
-    virtual std::unique_ptr<DBClientCursor> getMore(const std::string& ns,
-                                                    long long cursorId,
-                                                    int nToReturn,
-                                                    int options);
-
-    virtual void insert(const std::string& ns, BSONObj obj, int flags = 0);
-
-    virtual void insert(const std::string& ns, const std::vector<BSONObj>& v, int flags = 0);
-
-    virtual void remove(const std::string& ns, Query query, int flags);
-
-    virtual void update(const std::string& ns, Query query, BSONObj obj, int flags);
-
-    virtual bool call(Message& toSend, Message& response, bool assertOk, std::string* actualServer);
-    virtual void say(Message& toSend, bool isRetry = false, std::string* actualServer = 0);
-
-    virtual void killCursor(long long cursorID);
-
-    virtual std::string getServerAddress() const {
-        return _address;
-    }
-    virtual bool isFailed() const {
-        return false;
-    }
-    virtual bool isStillConnected();
-
-    int getMinWireVersion() final;
-    int getMaxWireVersion() final;
-
-    virtual std::string toString() const {
-        return _toString();
-    }
-
-    virtual BSONObj getLastErrorDetailed(
-        const std::string& db, bool fsync = false, bool j = false, int w = 0, int wtimeout = 0);
-    virtual BSONObj getLastErrorDetailed(bool fsync = false,
-                                         bool j = false,
-                                         int w = 0,
-                                         int wtimeout = 0);
-
-    virtual ConnectionString::ConnectionType type() const {
-        return ConnectionString::SYNC;
-    }
-
-    void setAllSoTimeouts(double socketTimeout);
-    double getSoTimeout() const {
-        return _socketTimeout;
-    }
-
-
-    virtual bool lazySupported() const {
-        return false;
-    }
-
-    // This override of runCommand intentionally calls findOne to construct a legacy
-    // OP_QUERY command. The reason for this is that delicate logic for targeting/locking
-    // config servers is in SyncClusterConnection::findOne, and refactoring that logic
-    // is both risky and of dubious value as we move to config server replica sets (CSRS).
-    bool runCommand(const std::string& dbname,
-                    const BSONObj& cmd,
-                    BSONObj& info,
-                    int options) final;
-
-    void setRequestMetadataWriter(rpc::RequestMetadataWriter writer) final;
-    void setReplyMetadataReader(rpc::ReplyMetadataReader reader) final;
-
-    /**
-     * Allow custom query processing through an external (e.g. mongos-only) service.
-     *
-     * Takes ownership of attached handler.
-     */
-    void attachQueryHandler(QueryHandler* handler);
-
-protected:
-    virtual void _auth(const BSONObj& params);
-
-private:
-    SyncClusterConnection(SyncClusterConnection& prev, double socketTimeout = 0);
-    std::string _toString() const;
-    bool _commandOnActive(const std::string& dbname,
-                          const BSONObj& cmd,
-                          BSONObj& info,
-                          int options = 0);
-    std::unique_ptr<DBClientCursor> _queryOnActive(const std::string& ns,
-                                                   Query query,
-                                                   int nToReturn,
-                                                   int nToSkip,
-                                                   const BSONObj* fieldsToReturn,
-                                                   int queryOptions,
-                                                   int batchSize);
-    int _lockType(const std::string& name);
-    void _checkLast();
-    void _connect(const std::string& host);
-
-    std::string _address;
-    std::vector<std::string> _connAddresses;
-    std::vector<DBClientConnection*> _conns;
-
-    std::vector<BSONObj> _lastErrors;
-
-    // Optionally attached by user
-    std::unique_ptr<QueryHandler> _customQueryHandler;
-
-    stdx::mutex _mutex;
-    std::map<std::string, int> _lockTypes;
-    // End mutex
-
-    double _socketTimeout;
-};
-
-/**
- * Interface for custom query processing for the SCC.
- * Allows plugging different host query behaviors for different types of queries.
- */
-class SyncClusterConnection::QueryHandler {
-public:
-    virtual ~QueryHandler(){};
-
-    /**
-     * Returns true if the query can be processed using this handler.
-     */
-    virtual bool canHandleQuery(const std::string& ns, Query query) = 0;
-
-    /**
-     * Returns a cursor on one of the hosts with the desired results for the query.
-     * May throw or return an empty unique_ptr on failure.
-     */
-    virtual std::unique_ptr<DBClientCursor> handleQuery(const std::vector<std::string>& hosts,
-                                                        const std::string& ns,
-                                                        Query query,
-                                                        int nToReturn,
-                                                        int nToSkip,
-                                                        const BSONObj* fieldsToReturn,
-                                                        int queryOptions,
-                                                        int batchSize) = 0;
-};
-
-class UpdateNotTheSame : public UserException {
-public:
-    UpdateNotTheSame(int code,
-                     const std::string& msg,
-                     const std::vector<std::string>& addrs,
-                     const std::vector<BSONObj>& lastErrors)
-        : UserException(code, msg), _addrs(addrs), _lastErrors(lastErrors) {
-        verify(_addrs.size() == _lastErrors.size());
-    }
-
-    virtual ~UpdateNotTheSame() throw() {}
-
-    unsigned size() const {
-        return _addrs.size();
-    }
-
-    std::pair<std::string, BSONObj> operator[](unsigned i) const {
-        return std::make_pair(_addrs[i], _lastErrors[i]);
-    }
-
-private:
-    std::vector<std::string> _addrs;
-    std::vector<BSONObj> _lastErrors;
-};
-};
diff --git a/src/mongo/db/s/set_shard_version_command.cpp b/src/mongo/db/s/set_shard_version_command.cpp
index e0e691117fe..4606720cb33 100644
--- a/src/mongo/db/s/set_shard_version_command.cpp
+++ b/src/mongo/db/s/set_shard_version_command.cpp
@@ -363,18 +363,6 @@ private:
                 return true;
             }
 
-            if (givenConnStr.type() == ConnectionString::SET &&
-                storedConnStr.type() == ConnectionString::SYNC) {
-                log() << "Detected upgrade from mirrored (SCCC) config servers to "
-                         "replica set (CSRS) config servers.  setShardVersion was given: "
-                      << givenConnStr
-                      << " for the config server connection string, but has stored: "
-                      << storedConnStr;
-                storedConnStr = givenConnStr;
-
-                return true;
-            }
-
             const auto& storedRawConfigString = storedConnStr.toString();
             if (storedRawConfigString == configdb) {
                 return true;
diff --git a/src/mongo/s/catalog/catalog_manager_common.cpp b/src/mongo/s/catalog/catalog_manager_common.cpp
index a7e81687631..dad99c9f3ee 100644
--- a/src/mongo/s/catalog/catalog_manager_common.cpp
+++ b/src/mongo/s/catalog/catalog_manager_common.cpp
@@ -95,10 +95,8 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
                                           ShardRegistry* shardRegistry,
                                           const ConnectionString& connectionString,
                                           const std::string* shardProposedName) {
-    if (connectionString.type() == ConnectionString::SYNC) {
-        return {ErrorCodes::BadValue,
-                "can't use sync cluster as a shard; for a replica set, "
-                "you have to use <setname>/<server1>,<server2>,..."};
+    if (connectionString.type() == ConnectionString::INVALID) {
+        return {ErrorCodes::BadValue, "Invalid connection string"};
     }
 
     if (shardProposedName && shardProposedName->empty()) {
diff --git a/src/mongo/s/catalog/legacy/config_upgrade.cpp b/src/mongo/s/catalog/legacy/config_upgrade.cpp
index e1ff04131bc..ea09db1dc00 100644
--- a/src/mongo/s/catalog/legacy/config_upgrade.cpp
+++ b/src/mongo/s/catalog/legacy/config_upgrade.cpp
@@ -34,7 +34,6 @@
 
 #include "mongo/client/connpool.h"
 #include "mongo/client/dbclientcursor.h"
-#include "mongo/client/syncclusterconnection.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/catalog/config_server_version.h"
 #include "mongo/s/catalog/dist_lock_manager.h"
@@ -168,24 +167,10 @@ VersionStatus isConfigVersionCompatible(const VersionType& versionInfo, string*
 Status _checkConfigServersAlive(const ConnectionString& configLoc) {
     BSONObj result;
     try {
-        if (configLoc.type() == ConnectionString::SYNC) {
-            ScopedDbConnection conn(configLoc, 30);
-            // TODO: Dynamic cast is bad, we need a better way of managing this op
-            // via the heirarchy (or not)
-            SyncClusterConnection* scc = dynamic_cast<SyncClusterConnection*>(conn.get());
-            fassert(16729, scc != NULL);
-            std::string errMsg;
-            if (!scc->prepare(errMsg)) {
-                return {ErrorCodes::HostUnreachable, errMsg};
-            }
-            conn.done();
-            return Status::OK();
-        } else {
-            ScopedDbConnection conn(configLoc, 30);
-            conn->runCommand("admin", BSON("fsync" << 1), result);
-            conn.done();
-            return getStatusFromCommandResult(result);
-        }
+        ScopedDbConnection conn(configLoc, 30);
+        conn->runCommand("admin", BSON("fsync" << 1), result);
+        conn.done();
+        return getStatusFromCommandResult(result);
     } catch (const DBException& e) {
         return e.toStatus();
     }
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
index 0d8cbfa7aae..86887c4826e 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
@@ -433,15 +433,15 @@ TEST_F(AddShardTest, StandaloneGenerateName) {
 TEST_F(AddShardTest, AddSCCCConnectionStringAsShard) {
     std::unique_ptr<RemoteCommandTargeterMock> targeter(
         stdx::make_unique<RemoteCommandTargeterMock>());
-    auto scccConn =
-        ConnectionString(ConnectionString::SYNC, "host1:12345,host2:12345,host3:12345", "");
-    targeter->setConnectionStringReturnValue(scccConn);
+    auto invalidConn =
+        ConnectionString("host1:12345,host2:12345,host3:12345", ConnectionString::INVALID);
+    targeter->setConnectionStringReturnValue(invalidConn);
 
-    auto future = launchAsync([this, scccConn] {
+    auto future = launchAsync([this, invalidConn] {
         const std::string shardName("StandaloneShard");
-        auto status = catalogManager()->addShard(operationContext(), &shardName, scccConn, 100);
+        auto status = catalogManager()->addShard(operationContext(), &shardName, invalidConn, 100);
         ASSERT_EQUALS(ErrorCodes::BadValue, status);
-        ASSERT_STRING_CONTAINS(status.getStatus().reason(), "can't use sync cluster as a shard");
+        ASSERT_STRING_CONTAINS(status.getStatus().reason(), "Invalid connection string");
     });
 
     future.timed_get(kFutureTimeout);
diff --git a/src/mongo/s/client/SConscript b/src/mongo/s/client/SConscript
index 2c7069db671..a72d106d893 100644
--- a/src/mongo/s/client/SConscript
+++ b/src/mongo/s/client/SConscript
@@ -31,7 +31,6 @@ env.Library(
     target='sharding_connection_hook',
     source=[
         'multi_host_query.cpp',
-        'scc_fast_query_handler.cpp',
         'sharding_connection_hook.cpp',
         'sharding_network_connection_hook.cpp',
     ],
diff --git a/src/mongo/s/client/scc_fast_query_handler.cpp b/src/mongo/s/client/scc_fast_query_handler.cpp
deleted file mode 100644
index c0871b9310f..00000000000
--- a/src/mongo/s/client/scc_fast_query_handler.cpp
+++ /dev/null
@@ -1,237 +0,0 @@
-/**
- *    Copyright (C) 2014 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kSharding
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/s/client/scc_fast_query_handler.h"
-
-#include <vector>
-
-#include "mongo/base/init.h"
-#include "mongo/bson/util/builder.h"
-#include "mongo/client/connpool.h"
-#include "mongo/client/dbclientcursor.h"
-#include "mongo/client/dbclientinterface.h"
-#include "mongo/db/namespace_string.h"
-#include "mongo/db/server_parameters.h"
-#include "mongo/util/log.h"
-
-namespace mongo {
-
-using std::unique_ptr;
-using std::endl;
-using std::string;
-using std::vector;
-
-/**
- * This parameter turns on fastest config reads for auth data only - *.system.users collections
- * and the "usersInfo" command.  This should be enough to prevent a non-responsive config from
- * hanging other operations in a cluster.
- */
-MONGO_EXPORT_SERVER_PARAMETER(internalSCCAllowFastestAuthConfigReads, bool, false);
-
-/**
- * TESTING ONLY.
- *
- * This parameter turns on fastest config reads for *all* config.* collections except those
- * deemed extremely critical (config.version, config.locks).
- *
- * NOT FOR PRODUCTION USE.
- */
-MONGO_EXPORT_SERVER_PARAMETER(internalSCCAllowFastestMetadataConfigReads, bool, false);
-
-//
-// The shared environment for MultiHostQueries
-//
-
-namespace {
-
-class MultiQueryEnv : public MultiHostQueryOp::SystemEnv {
-public:
-    virtual ~MultiQueryEnv() {}
-
-    Date_t currentTimeMillis();
-
-    StatusWith<DBClientCursor*> doBlockingQuery(const ConnectionString& host,
-                                                const QuerySpec& query);
-};
-
-StatusWith<DBClientCursor*> MultiQueryEnv::doBlockingQuery(const ConnectionString& host,
-                                                           const QuerySpec& query) {
-    //
-    // Note that this function may be active during shutdown.  This means that we must
-    // handle connection pool shutdown exceptions (uasserts).  The results of this
-    // operation must then be correctly discarded by the calling thread.
-    //
-
-    unique_ptr<DBClientCursor> cursor;
-
-    try {
-        ScopedDbConnection conn(host, 30.0 /* timeout secs */);
-
-        cursor = conn->query(query.ns(),
-                             query.filter(),
-                             query.ntoreturn(),
-                             query.ntoskip(),
-                             query.fieldsPtr(),
-                             query.options(),
-                             0);
-
-        if (NULL == cursor.get()) {
-            // Confusingly, exceptions here are written to the log, not thrown
-
-            StringBuilder builder;
-            builder << "error querying server " << host.toString()
-                    << ", could not create cursor for query";
-
-            warning() << builder.str() << endl;
-            return StatusWith<DBClientCursor*>(ErrorCodes::HostUnreachable, builder.str());
-        }
-
-        // Confusingly, this *detaches* the cursor from the connection it was established
-        // on, further getMore calls will use a (potentially different) ScopedDbConnection.
-        //
-        // Calls done() too.
-        cursor->attach(&conn);
-    } catch (const DBException& ex) {
-        return StatusWith<DBClientCursor*>(ex.toStatus());
-    }
-
-    return StatusWith<DBClientCursor*>(cursor.release());
-}
-
-Date_t MultiQueryEnv::currentTimeMillis() {
-    return jsTime();
-}
-}
-
-// Shared networking environment which executes queries.
-// NOTE: This environment must stay in scope as long as per-host threads are executing queries -
-// i.e. for the lifetime of the server.
-// Once the thread pools are disposed and connections shut down, the per-host threads should
-// be self-contained and correctly shut down after discarding the results.
-static MultiQueryEnv* _multiQueryEnv;
-
-namespace {
-
-//
-// Create the shared multi-query environment at startup
-//
-
-MONGO_INITIALIZER(InitMultiQueryEnv)(InitializerContext* context) {
-    // Leaked intentionally
-    _multiQueryEnv = new MultiQueryEnv();
-    return Status::OK();
-}
-}
-
-//
-// Per-SCC handling of queries
-//
-
-SCCFastQueryHandler::SCCFastQueryHandler() : _queryThreads(1, false) {}
-
-bool SCCFastQueryHandler::canHandleQuery(const string& ns, Query query) {
-    if (!internalSCCAllowFastestAuthConfigReads && !internalSCCAllowFastestMetadataConfigReads) {
-        return false;
-    }
-
-    //
-    // More operations can be added here
-    //
-    // NOTE: Not all operations actually pass through the SCC _queryOnActive path - notable
-    // exceptions include anything related to direct query ops and direct operations for
-    // connection maintenance.
-    //
-
-    NamespaceString nss(ns);
-    if (nss.isCommand()) {
-        BSONObj cmdObj = query.getFilter();
-        string cmdName = cmdObj.firstElement().fieldName();
-        if (cmdName == "usersInfo")
-            return true;
-    } else if (nss.coll() == "system.users") {
-        return true;
-    }
-
-    //
-    // Allow fastest config reads for all collections except for those involved in locks and
-    // cluster versioning.
-    //
-
-    if (!internalSCCAllowFastestMetadataConfigReads)
-        return false;
-
-    if (nss.db() != "config")
-        return false;
-
-    if (nss.coll() != "version" && nss.coll() != "locks" && nss.coll() != "lockpings") {
-        return true;
-    }
-
-    return false;
-}
-
-static vector<ConnectionString> getHosts(const vector<string> hostStrings) {
-    vector<ConnectionString> hosts;
-    for (const auto& host : hostStrings) {
-        hosts.push_back(fassertStatusOK(28738, ConnectionString::parse(host)));
-    }
-
-    return hosts;
-}
-
-unique_ptr<DBClientCursor> SCCFastQueryHandler::handleQuery(const vector<string>& hostStrings,
-                                                            const string& ns,
-                                                            Query query,
-                                                            int nToReturn,
-                                                            int nToSkip,
-                                                            const BSONObj* fieldsToReturn,
-                                                            int queryOptions,
-                                                            int batchSize) {
-    MultiHostQueryOp queryOp(_multiQueryEnv, &_queryThreads);
-
-    QuerySpec querySpec(ns,
-                        query.obj,
-                        fieldsToReturn ? *fieldsToReturn : BSONObj(),
-                        nToSkip,
-                        nToReturn,
-                        queryOptions);
-
-    // TODO: Timeout must be passed down here as well - 30s timeout may not be applicable for
-    // all operations handled.
-    StatusWith<DBClientCursor*> status =
-        queryOp.queryAny(getHosts(hostStrings), querySpec, 30 * 1000);
-    uassertStatusOK(status.getStatus());
-
-    unique_ptr<DBClientCursor> cursor(status.getValue());
-    return cursor;
-}
-}
diff --git a/src/mongo/s/client/scc_fast_query_handler.h b/src/mongo/s/client/scc_fast_query_handler.h
deleted file mode 100644
index c2079e717ff..00000000000
--- a/src/mongo/s/client/scc_fast_query_handler.h
+++ /dev/null
@@ -1,72 +0,0 @@
-/**
- *    Copyright (C) 2014 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#pragma once
-
-#include "mongo/client/syncclusterconnection.h"
-#include "mongo/s/client/multi_host_query.h"
-
-namespace mongo {
-
-/**
- * Query handler that plugs in to a SyncClusterConnection and allows query on fastest host
- * (if enabled).
- *
- * Glue code which shields the MultiHostQuery and server parameters from the separate client
- * module which knows about neither.
- *
- * There is a *single* SCCFastQueryHandler for every SCC.  Each SCCFastQueryHandler contains
- * its own thread pool (lazily initialized) so that at maximum there is a thread-per-SCC-host
- * and this thread may have an open connection to the host until it times out.
- * If using the "fastestConfigReads" options, clients must be ready for the additional thread
- * and connection load when configs are slow.
- */
-class SCCFastQueryHandler : public SyncClusterConnection::QueryHandler {
-public:
-    SCCFastQueryHandler();
-
-    virtual ~SCCFastQueryHandler() {}
-
-    virtual bool canHandleQuery(const std::string& ns, Query query);
-
-    virtual std::unique_ptr<DBClientCursor> handleQuery(const std::vector<std::string>& hostStrings,
-                                                        const std::string& ns,
-                                                        Query query,
-                                                        int nToReturn,
-                                                        int nToSkip,
-                                                        const BSONObj* fieldsToReturn,
-                                                        int queryOptions,
-                                                        int batchSize);
-
-private:
-    // The thread pool itself is scoped to the handler and SCC, and lazily creates threads
-    // per-host as needed.  This ensures query starvation cannot occur due to other active
-    // client threads - though a thread must be created for every client.
-    HostThreadPools _queryThreads;
-};
-}
diff --git a/src/mongo/s/client/shard_registry.cpp b/src/mongo/s/client/shard_registry.cpp
index 4965f58da85..8cd38e66d9e 100644
--- a/src/mongo/s/client/shard_registry.cpp
+++ b/src/mongo/s/client/shard_registry.cpp
@@ -423,11 +423,7 @@ void ShardRegistry::appendConnectionStats(executor::ConnectionPoolStats* stats)
 }
 
 void ShardRegistry::_addConfigShard_inlock() {
-    _addShard_inlock("config",
-                     _configServerCS,
-                     _configServerCS.type() == ConnectionString::SYNC
-                         ? nullptr
-                         : _targeterFactory->create(_configServerCS));
+    _addShard_inlock("config", _configServerCS, _targeterFactory->create(_configServerCS));
 }
 
 void ShardRegistry::updateReplSetHosts(const ConnectionString& newConnString) {
diff --git a/src/mongo/s/client/sharding_connection_hook.cpp b/src/mongo/s/client/sharding_connection_hook.cpp
index 7f325611db9..d3cbd242c04 100644
--- a/src/mongo/s/client/sharding_connection_hook.cpp
+++ b/src/mongo/s/client/sharding_connection_hook.cpp
@@ -43,7 +43,6 @@
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/rpc/metadata/audit_metadata.h"
 #include "mongo/rpc/metadata/config_server_metadata.h"
-#include "mongo/s/client/scc_fast_query_handler.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/cluster_last_error_info.h"
 #include "mongo/s/grid.h"
@@ -115,6 +114,11 @@ ShardingConnectionHook::ShardingConnectionHook(bool shardedConnections)
     : _shardedConnections(shardedConnections) {}
 
 void ShardingConnectionHook::onCreate(DBClientBase* conn) {
+    if (conn->type() == ConnectionString::INVALID) {
+        throw UserException(ErrorCodes::BadValue,
+                            str::stream() << "Unrecognized connection string.");
+    }
+
     // Authenticate as the first thing we do
     // NOTE: Replica set authentication allows authentication against *any* online host
     if (getGlobalAuthorizationManager()->isAuthEnabled()) {
@@ -136,12 +140,6 @@ void ShardingConnectionHook::onCreate(DBClientBase* conn) {
             return _shardingRequestMetadataWriter(_shardedConnections, metadataBob, hostStringData);
         });
 
-    if (conn->type() == ConnectionString::SYNC) {
-        throw UserException(ErrorCodes::UnsupportedFormat,
-                            str::stream() << "Unrecognized connection string type: " << conn->type()
-                                          << ".");
-    }
-
     if (conn->type() == ConnectionString::MASTER) {
         BSONObj isMasterResponse;
         if (!conn->runCommand("admin", BSON("ismaster" << 1), isMasterResponse)) {
diff --git a/src/mongo/s/mongos_options.cpp b/src/mongo/s/mongos_options.cpp
index 526cf3f6925..17e85baff74 100644
--- a/src/mongo/s/mongos_options.cpp
+++ b/src/mongo/s/mongos_options.cpp
@@ -254,41 +254,32 @@ Status storeMongosOptions(const moe::Environment& params, const std::vector<std:
         return Status(ErrorCodes::BadValue, "error: no args for --configdb");
     }
 
-    {
-        std::string configdbString = params["sharding.configDB"].as<std::string>();
-
-        auto configdbConnectionString = ConnectionString::parse(configdbString);
-        if (!configdbConnectionString.isOK()) {
-            return Status(ErrorCodes::BadValue,
-                          str::stream() << "Invalid configdb connection string: "
-                                        << configdbConnectionString.getStatus().toString());
-        }
-
-        std::vector<HostAndPort> seedServers;
-        for (const auto& host : configdbConnectionString.getValue().getServers()) {
-            seedServers.push_back(host);
-            if (!seedServers.back().hasPort()) {
-                seedServers.back() = HostAndPort{host.host(), ServerGlobalParams::ConfigServerPort};
-            }
-        }
+    std::string configdbString = params["sharding.configDB"].as<std::string>();
 
-        mongosGlobalParams.configdbs =
-            ConnectionString{configdbConnectionString.getValue().type(),
-                             seedServers,
-                             configdbConnectionString.getValue().getSetName()};
+    auto configdbConnectionString = ConnectionString::parse(configdbString);
+    if (!configdbConnectionString.isOK()) {
+        return configdbConnectionString.getStatus();
     }
 
-    std::vector<HostAndPort> configServers = mongosGlobalParams.configdbs.getServers();
-
-    if (mongosGlobalParams.configdbs.type() != ConnectionString::SYNC &&
-        mongosGlobalParams.configdbs.type() != ConnectionString::SET &&
-        mongosGlobalParams.configdbs.type() != ConnectionString::MASTER) {
+    if (configdbConnectionString.getValue().type() != ConnectionString::SET) {
         return Status(ErrorCodes::BadValue,
-                      str::stream() << "Invalid config server value "
-                                    << mongosGlobalParams.configdbs.toString());
+                      str::stream() << "configdb supports only replica set connection string");
     }
 
-    if (configServers.size() < 3) {
+    std::vector<HostAndPort> seedServers;
+    for (const auto& host : configdbConnectionString.getValue().getServers()) {
+        seedServers.push_back(host);
+        if (!seedServers.back().hasPort()) {
+            seedServers.back() = HostAndPort{host.host(), ServerGlobalParams::ConfigServerPort};
+        }
+    }
+
+    mongosGlobalParams.configdbs =
+        ConnectionString{configdbConnectionString.getValue().type(),
+                         seedServers,
+                         configdbConnectionString.getValue().getSetName()};
+
+    if (mongosGlobalParams.configdbs.getServers().size() < 3) {
         warning() << "Running a sharded cluster with fewer than 3 config servers should only be "
                      "done for testing purposes and is not recommended for production.";
     }
diff --git a/src/mongo/s/query/cluster_find.cpp b/src/mongo/s/query/cluster_find.cpp
index 948e12b2af6..8f697a37595 100644
--- a/src/mongo/s/query/cluster_find.cpp
+++ b/src/mongo/s/query/cluster_find.cpp
@@ -190,7 +190,7 @@ StatusWith<CursorId> runQueryWithoutRetrying(OperationContext* txn,
     // Use read pref to target a particular host from each shard. Also construct the find command
     // that we will forward to each shard.
     for (const auto& shard : shards) {
-        invariant(!shard->isConfig() || shard->getConnString().type() != ConnectionString::SYNC);
+        invariant(!shard->isConfig() || shard->getConnString().type() != ConnectionString::INVALID);
 
         // Build the find command, and attach shard version if necessary.
         BSONObjBuilder cmdBuilder;
diff --git a/src/mongo/s/sharding_initialization.cpp b/src/mongo/s/sharding_initialization.cpp
index 0ad8aa554f5..437e11e4e48 100644
--- a/src/mongo/s/sharding_initialization.cpp
+++ b/src/mongo/s/sharding_initialization.cpp
@@ -36,7 +36,6 @@
 
 #include "mongo/base/status.h"
 #include "mongo/client/remote_command_targeter_factory_impl.h"
-#include "mongo/client/syncclusterconnection.h"
 #include "mongo/db/audit.h"
 #include "mongo/db/server_options.h"
 #include "mongo/db/service_context.h"
@@ -177,15 +176,10 @@ std::unique_ptr<TaskExecutorPool> makeTaskExecutorPool(std::unique_ptr<NetworkIn
 Status initializeGlobalShardingState(OperationContext* txn,
                                      const ConnectionString& configCS,
                                      bool allowNetworking) {
-    if (configCS.type() == ConnectionString::SYNC) {
-        return {ErrorCodes::UnsupportedFormat,
-                "SYNC config server connection string is not allowed."};
+    if (configCS.type() == ConnectionString::INVALID) {
+        return {ErrorCodes::BadValue, "Unrecognized connection string."};
     }
 
-    SyncClusterConnection::setConnectionValidationHook(
-        [](const HostAndPort& target, const executor::RemoteCommandResponse& isMasterReply) {
-            return ShardingNetworkConnectionHook::validateHostImpl(target, isMasterReply);
-        });
     auto network =
         executor::makeNetworkInterface("NetworkInterfaceASIO-ShardRegistry",
                                        stdx::make_unique<ShardingNetworkConnectionHook>(),
diff --git a/src/mongo/s/version_manager.cpp b/src/mongo/s/version_manager.cpp
index 4fb45bdbccb..7cbb2787e82 100644
--- a/src/mongo/s/version_manager.cpp
+++ b/src/mongo/s/version_manager.cpp
@@ -161,12 +161,6 @@ DBClientBase* getVersionable(DBClientBase* conn) {
             return nullptr;
         case ConnectionString::MASTER:
             return conn;
-        case ConnectionString::SYNC:
-            massert(15906,
-                    str::stream() << "cannot set version or shard on sync connection "
-                                  << conn->toString(),
-                    false);
-            return nullptr;
         case ConnectionString::CUSTOM:
             massert(16334,
                     str::stream() << "cannot set version or shard on custom connection "
diff --git a/src/mongo/shell/servers_misc.js b/src/mongo/shell/servers_misc.js
index f27cd754b58..8f3bff9d9e0 100644
--- a/src/mongo/shell/servers_misc.js
+++ b/src/mongo/shell/servers_misc.js
@@ -201,53 +201,7 @@ allocatePorts = function(numPorts) {
     return ports;
 };
 
-SyncCCTest = function(testName, extraMongodOptions) {
-    this._testName = testName;
-    this._connections = [];
-
-    for (var i = 0; i < 3; i++) {
-        this._connections.push(MongoRunner.runMongod(extraMongodOptions));
-    }
-
-    this.url = this._connections.map(function(z) {
-        return z.name;
-    }).join(",");
-    this.conn = new Mongo(this.url);
-};
-
-SyncCCTest.prototype.stop = function() {
-    for (var i = 0; i < this._connections.length; i++) {
-        _stopMongoProgram(30000 + i);
-    }
-
-    print('*** ' + this._testName + " completed successfully ***");
-};
-
-SyncCCTest.prototype.checkHashes = function(dbname, msg) {
-    var hashes = this._connections.map(function(z) {
-        return z.getDB(dbname).runCommand("dbhash");
-    });
-
-    for (var i = 1; i < hashes.length; i++) {
-        assert.eq(hashes[0].md5,
-                  hashes[i].md5,
-                  "checkHash on " + dbname + " " + msg + "\n" + tojson(hashes));
-    }
-};
-
-SyncCCTest.prototype.tempKill = function(num) {
-    num = num || 0;
-    MongoRunner.stopMongod(this._connections[num]);
-};
-
-SyncCCTest.prototype.tempStart = function(num) {
-    num = num || 0;
-    var old = this._connections[num];
-    this._connections[num] = MongoRunner.runMongod(
-        {restart: true, cleanData: false, port: old.port, dbpath: old.dbpath});
-};
-
-function startParallelShell(jsCode, port, noConnect) {
+function startParallelShell( jsCode, port, noConnect ) {
     var args = ["mongo"];
 
     if (typeof db == "object") {
diff --git a/src/mongo/shell/shardingtest.js b/src/mongo/shell/shardingtest.js
index 6651057143e..a167ac1c8e5 100644
--- a/src/mongo/shell/shardingtest.js
+++ b/src/mongo/shell/shardingtest.js
@@ -30,9 +30,8 @@
  *       configuration object(s)(*). @see MongoRunner.runMongod
  *
  *     config {number|Object|Array.<Object>}: number of config server or
- *       config server configuration object(s)(*). If this field has 3 or
- *       more members, it implies other.sync = true. @see MongoRunner.runMongod
- *
+ *       config server configuration object(s)(*). @see MongoRunner.runMongod
+ * 
  *     (*) There are two ways For multiple configuration objects.
  *       (1) Using the object format. Example:
  *
@@ -58,9 +57,7 @@
  *
  *       shardOptions {Object}: same as the shards property above.
  *          Can be used to specify options that are common all shards.
- *
- *       sync {boolean}: Use SyncClusterConnection, and readies
- *          1 or 3 config servers, based on the value of numConfigs.
+ * 
  *       configOptions {Object}: same as the config property above.
  *          Can be used to specify options that are common all config servers.
  *       mongosOptions {Object}: same as the mongos property above.
@@ -1182,133 +1179,57 @@ var ShardingTest = function(params) {
         rsConn.rs = rs;
     }
 
-    // Default to using 3-node legacy config servers if jsTestOptions().useLegacyOptions is true
-    // and the user didn't explicity specify a different config server configuration
-    if (jsTestOptions().useLegacyConfigServers && otherParams.sync !== false &&
-        (typeof(otherParams.config) === 'undefined' || numConfigs === 3)) {
-        otherParams.sync = true;
-    }
-
     this._configServers = [];
 
-    // Start the config servers
-    if (otherParams.sync) {
-        if (numConfigs !== 1 && numConfigs !== 3) {
-            throw Error('Sync config servers only supported with 1 or 3 nodes');
-        }
-
-        var configNames = [];
-        for (var i = 0; i < numConfigs; i++) {
-            var options = {
-                useHostname: otherParams.useHostname,
-                noJournalPrealloc: otherParams.nopreallocj,
-                pathOpts: Object.merge(pathOpts, {config: i}),
-                dbpath: "$testName-config$config",
-                keyFile: keyFile,
-                // Ensure that journaling is always enabled for config servers.
-                journal: "",
-                configsvr: ""
-            };
-
-            if (otherParams.configOptions && otherParams.configOptions.binVersion) {
-                otherParams.configOptions.binVersion =
-                    MongoRunner.versionIterator(otherParams.configOptions.binVersion);
-            }
-
-            options = Object.merge(options, otherParams.configOptions);
-            options = Object.merge(options, otherParams["c" + i]);
-
-            options.port = options.port || allocatePort();
-
-            if (otherParams.useBridge) {
-                var bridgeOptions =
-                    Object.merge(otherParams.bridgeOptions, options.bridgeOptions || {});
-                bridgeOptions = Object.merge(
-                    bridgeOptions,
-                    {
-                      hostName: otherParams.useHostname ? hostName : "localhost",
-                      // The mongod processes identify themselves to mongobridge as host:port, where
-                      // the host is the actual hostname of the machine and not localhost.
-                      dest: hostName + ":" + options.port,
-                    });
-
-                var bridge = new MongoBridge(bridgeOptions);
-            }
-
-            var conn = MongoRunner.runMongod(options);
-            if (!conn) {
-                throw new Error("Failed to start config server " + i);
-            }
-
-            if (otherParams.useBridge) {
-                bridge.connectToBridge();
-                this._configServers.push(bridge);
-                unbridgedConfigServers.push(conn);
-                configNames.push(bridge.host);
-            } else {
-                this._configServers.push(conn);
-                configNames.push(conn.name);
-            }
-
-            _alldbpaths.push(testName + "-config" + i);
-            this["config" + i] = this._configServers[i];
-            this["c" + i] = this._configServers[i];
-        }
-
-        this._configDB = configNames.join(',');
-    } else {
-        // Using replica set for config servers
-        var rstOptions = {
-            useHostName: otherParams.useHostname,
-            useBridge: otherParams.useBridge,
-            bridgeOptions: otherParams.bridgeOptions,
-            keyFile: keyFile,
-            name: testName + "-configRS",
-        };
-
-        // when using CSRS, always use wiredTiger as the storage engine
-        var startOptions = {
-            pathOpts: pathOpts,
-            // Ensure that journaling is always enabled for config servers.
-            journal: "",
-            configsvr: "",
-            noJournalPrealloc: otherParams.nopreallocj,
-            storageEngine: "wiredTiger",
-        };
-
-        if (otherParams.configOptions && otherParams.configOptions.binVersion) {
-            otherParams.configOptions.binVersion =
-                MongoRunner.versionIterator(otherParams.configOptions.binVersion);
-        }
+    // Using replica set for config servers
+    var rstOptions = { useHostName : otherParams.useHostname,
+                       useBridge : otherParams.useBridge,
+                       bridgeOptions : otherParams.bridgeOptions,
+                       keyFile : keyFile,
+                       name: testName + "-configRS",
+                     };
+
+    // when using CSRS, always use wiredTiger as the storage engine
+    var startOptions = { pathOpts: pathOpts,
+                         // Ensure that journaling is always enabled for config servers.
+                         journal : "",
+                         configsvr : "",
+                         noJournalPrealloc : otherParams.nopreallocj,
+                         storageEngine : "wiredTiger",
+                       };
+
+    if (otherParams.configOptions && otherParams.configOptions.binVersion) {
+        otherParams.configOptions.binVersion =
+            MongoRunner.versionIterator(otherParams.configOptions.binVersion);
+    }
 
-        startOptions = Object.merge(startOptions, otherParams.configOptions);
-        rstOptions = Object.merge(rstOptions, otherParams.configReplSetTestOptions);
+    startOptions = Object.merge(startOptions, otherParams.configOptions);
+    rstOptions = Object.merge(rstOptions, otherParams.configReplSetTestOptions);
 
-        var nodeOptions = [];
-        for (var i = 0; i < numConfigs; ++i) {
-            nodeOptions.push(otherParams["c" + i] || {});
-        }
+    var nodeOptions = [];
+    for (var i = 0; i < numConfigs; ++i) {
+        nodeOptions.push(otherParams["c" + i] || {});
+    }
 
-        rstOptions.nodes = nodeOptions;
+    rstOptions.nodes = nodeOptions;
 
-        this.configRS = new ReplSetTest(rstOptions);
-        this.configRS.startSet(startOptions);
+    this.configRS = new ReplSetTest(rstOptions);
+    this.configRS.startSet(startOptions);
 
-        var config = this.configRS.getReplSetConfig();
-        config.configsvr = true;
-        config.settings = config.settings || {};
-        var initiateTimeout = otherParams.rsOptions && otherParams.rsOptions.initiateTimeout;
-        this.configRS.initiate(config, null, initiateTimeout);
+    var config = this.configRS.getReplSetConfig();
+    config.configsvr = true;
+    config.settings = config.settings || {};
+    var initiateTimeout = otherParams.rsOptions && otherParams.rsOptions.initiateTimeout;
+    this.configRS.initiate(config, null, initiateTimeout);
 
-        this.configRS.getPrimary();  // Wait for master to be elected before starting mongos
+    this.configRS.getPrimary(); // Wait for master to be elected before starting mongos
 
-        this._configDB = this.configRS.getURL();
-        this._configServers = this.configRS.nodes;
-        for (var i = 0; i < numConfigs; ++i) {
-            var conn = this._configServers[i];
-            this["config" + i] = conn;
-            this["c" + i] = conn;
-        }
+    this._configDB = this.configRS.getURL();
+    this._configServers = this.configRS.nodes;
+    for (var i = 0; i < numConfigs; ++i) {
+        var conn = this._configServers[i];
+        this["config" + i] = conn;
+        this["c" + i] = conn;
     }
 
     printjson("config servers: " + this._configDB);
diff --git a/src/mongo/shell/utils.js b/src/mongo/shell/utils.js
index 75bf3b9f7f8..2cb54bb1d2a 100644
--- a/src/mongo/shell/utils.js
+++ b/src/mongo/shell/utils.js
@@ -186,7 +186,6 @@ jsTestOptions = function() {
               authMechanism: TestData.authMechanism,
               adminUser: TestData.adminUser || "admin",
               adminPassword: TestData.adminPassword || "password",
-              useLegacyConfigServers: TestData.useLegacyConfigServers || false,
               useLegacyReplicationProtocol: TestData.useLegacyReplicationProtocol || false,
               enableMajorityReadConcern: TestData.enableMajorityReadConcern,
               enableEncryption: TestData.enableEncryption,