SERVER-31061 Add `mongo+srv://` support for URIs.

The shell now supports parsing and handling `mongo+srv://` style URIs,
as part of the DNS Seedlist support.  These URIs require DNS SRV and
TXT record lookups, for extra configuration options.  The shell also
supports a (limited) form of connection-failover -- when initially
connecting to a non-replica-set cluster, the shell will try each
host listed, in order, until a connection can be established.

12 files changed, 328 insertions, 129 deletions

diff --git a/src/mongo/client/SConscript b/src/mongo/client/SConscript
index 16dd55dafa0..1956ae58109 100644
--- a/src/mongo/client/SConscript
+++ b/src/mongo/client/SConscript
@@ -24,6 +24,9 @@ env.Library(
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/util/net/network',
+    ],
+    LIBDEPS_PRIVATE=[
+        '$BUILD_DIR/mongo/util/dns_query',
     ]
 )
 
diff --git a/src/mongo/client/connection_string.cpp b/src/mongo/client/connection_string.cpp
index 16a6e78440d..5e8a5f4e0bb 100644
--- a/src/mongo/client/connection_string.cpp
+++ b/src/mongo/client/connection_string.cpp
@@ -121,9 +121,6 @@ void ConnectionString::_finishInit() {
             uassert(ErrorCodes::FailedToParse,
                     "Cannot specify a replica set name for a ConnectionString of type MASTER",
                     _setName.empty());
-            uassert(ErrorCodes::FailedToParse,
-                    "ConnectionStrings of type MASTER must contain exactly one server",
-                    _servers.size() == 1);
             break;
         case SET:
             uassert(ErrorCodes::FailedToParse,
diff --git a/src/mongo/client/connection_string.h b/src/mongo/client/connection_string.h
index 2e888b56dad..0467a77dce3 100644
--- a/src/mongo/client/connection_string.h
+++ b/src/mongo/client/connection_string.h
@@ -28,6 +28,7 @@
 
 #pragma once
 
+#include <memory>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -119,10 +120,10 @@ public:
     bool operator==(const ConnectionString& other) const;
     bool operator!=(const ConnectionString& other) const;
 
-    DBClientBase* connect(StringData applicationName,
-                          std::string& errmsg,
-                          double socketTimeout = 0,
-                          const MongoURI* uri = nullptr) const;
+    std::unique_ptr<DBClientBase> connect(StringData applicationName,
+                                          std::string& errmsg,
+                                          double socketTimeout = 0,
+                                          const MongoURI* uri = nullptr) const;
 
     static StatusWith<ConnectionString> parse(const std::string& url);
 
@@ -139,9 +140,9 @@ public:
         virtual ~ConnectionHook() {}
 
         // Returns an alternative connection object for a string
-        virtual DBClientBase* connect(const ConnectionString& c,
-                                      std::string& errmsg,
-                                      double socketTimeout) = 0;
+        virtual std::unique_ptr<DBClientBase> connect(const ConnectionString& c,
+                                                      std::string& errmsg,
+                                                      double socketTimeout) = 0;
     };
 
     static void setConnectionHook(ConnectionHook* hook) {
diff --git a/src/mongo/client/connection_string_connect.cpp b/src/mongo/client/connection_string_connect.cpp
index e4c99dd37e1..d824fa6be78 100644
--- a/src/mongo/client/connection_string_connect.cpp
+++ b/src/mongo/client/connection_string_connect.cpp
@@ -46,10 +46,10 @@ namespace mongo {
 stdx::mutex ConnectionString::_connectHookMutex;
 ConnectionString::ConnectionHook* ConnectionString::_connectHook = NULL;
 
-DBClientBase* ConnectionString::connect(StringData applicationName,
-                                        std::string& errmsg,
-                                        double socketTimeout,
-                                        const MongoURI* uri) const {
+std::unique_ptr<DBClientBase> ConnectionString::connect(StringData applicationName,
+                                                        std::string& errmsg,
+                                                        double socketTimeout,
+                                                        const MongoURI* uri) const {
     MongoURI newURI{};
     if (uri) {
         newURI = *uri;
@@ -57,15 +57,18 @@ DBClientBase* ConnectionString::connect(StringData applicationName,
 
     switch (_type) {
         case MASTER: {
-            auto c = stdx::make_unique<DBClientConnection>(true, 0, std::move(newURI));
-
-            c->setSoTimeout(socketTimeout);
-            LOG(1) << "creating new connection to:" << _servers[0];
-            if (!c->connect(_servers[0], applicationName, errmsg)) {
-                return 0;
+            for (const auto& server : _servers) {
+                auto c = stdx::make_unique<DBClientConnection>(true, 0, newURI);
+
+                c->setSoTimeout(socketTimeout);
+                LOG(1) << "creating new connection to:" << server;
+                if (!c->connect(server, applicationName, errmsg)) {
+                    continue;
+                }
+                LOG(1) << "connected connection!";
+                return std::move(c);
             }
-            LOG(1) << "connected connection!";
-            return c.release();
+            return nullptr;
         }
 
         case SET: {
@@ -74,9 +77,9 @@ DBClientBase* ConnectionString::connect(StringData applicationName,
             if (!set->connect()) {
                 errmsg = "connect failed to replica set ";
                 errmsg += toString();
-                return 0;
+                return nullptr;
             }
-            return set.release();
+            return std::move(set);
         }
 
         case CUSTOM: {
@@ -91,7 +94,7 @@ DBClientBase* ConnectionString::connect(StringData applicationName,
                     _connectHook);
 
             // Double-checked lock, since this will never be active during normal operation
-            DBClientBase* replacementConn = _connectHook->connect(*this, errmsg, socketTimeout);
+            auto replacementConn = _connectHook->connect(*this, errmsg, socketTimeout);
 
             log() << "replacing connection to " << this->toString() << " with "
                   << (replacementConn ? replacementConn->getServerAddress() : "(empty)");
diff --git a/src/mongo/client/connpool.cpp b/src/mongo/client/connpool.cpp
index 30325079fab..6c5a3d9cdfa 100644
--- a/src/mongo/client/connpool.cpp
+++ b/src/mongo/client/connpool.cpp
@@ -256,7 +256,7 @@ DBClientBase* DBConnectionPool::get(const ConnectionString& url, double socketTi
     // If no connections for this host are available in the PoolForHost (that is, all the
     // connections have been checked out, or none have been created yet), create a new connection.
     string errmsg;
-    c = url.connect(StringData(), errmsg, socketTimeout);
+    c = url.connect(StringData(), errmsg, socketTimeout).release();
     uassert(13328, _name + ": connect failed " + url.toString() + " : " + errmsg, c);
 
     return _finishCreate(url.toString(), socketTimeout, c);
@@ -277,7 +277,7 @@ DBClientBase* DBConnectionPool::get(const string& host, double socketTimeout) {
     const ConnectionString cs(uassertStatusOK(ConnectionString::parse(host)));
 
     string errmsg;
-    c = cs.connect(StringData(), errmsg, socketTimeout);
+    c = cs.connect(StringData(), errmsg, socketTimeout).release();
     if (!c)
         throw SocketException(SocketException::CONNECT_ERROR,
                               host,
diff --git a/src/mongo/client/mongo_uri.cpp b/src/mongo/client/mongo_uri.cpp
index e2356881290..e7c500d719b 100644
--- a/src/mongo/client/mongo_uri.cpp
+++ b/src/mongo/client/mongo_uri.cpp
@@ -34,24 +34,26 @@
 
 #include <utility>
 
+#include <boost/algorithm/string/case_conv.hpp>
+#include <boost/algorithm/string/classification.hpp>
+#include <boost/algorithm/string/find_iterator.hpp>
+#include <boost/algorithm/string/predicate.hpp>
+
 #include "mongo/base/status_with.h"
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/client/dbclientinterface.h"
 #include "mongo/client/sasl_client_authenticate.h"
 #include "mongo/db/namespace_string.h"
+#include "mongo/util/dns_query.h"
 #include "mongo/util/hex.h"
 #include "mongo/util/mongoutils/str.h"
 
-#include <boost/algorithm/string/case_conv.hpp>
-#include <boost/algorithm/string/classification.hpp>
-#include <boost/algorithm/string/find_iterator.hpp>
-#include <boost/algorithm/string/predicate.hpp>
-
 namespace {
 constexpr std::array<char, 16> hexits{
     '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
 const mongo::StringData kURIPrefix{"mongodb://"};
-}
+const mongo::StringData kURISRVPrefix{"mongodb+srv://"};
+}  // namespace
 
 /**
  * RFC 3986 Section 2.1 - Percent Encoding
@@ -94,7 +96,8 @@ namespace mongo {
 namespace {
 
 /**
- * Helper Method for MongoURI::parse() to split a string into exactly 2 pieces by a char delimeter
+ * Helper Method for MongoURI::parse() to split a string into exactly 2 pieces by a char
+ * delimeter.
  */
 std::pair<StringData, StringData> partitionForward(StringData str, const char c) {
     const auto delim = str.find(c);
@@ -105,8 +108,8 @@ std::pair<StringData, StringData> partitionForward(StringData str, const char c)
 }
 
 /**
- * Helper method for MongoURI::parse() to split a string into exactly 2 pieces by a char delimiter
- * searching backward from the end of the string.
+ * Helper method for MongoURI::parse() to split a string into exactly 2 pieces by a char
+ * delimiter searching backward from the end of the string.
  */
 std::pair<StringData, StringData> partitionBackward(StringData str, const char c) {
     const auto delim = str.rfind(c);
@@ -121,17 +124,17 @@ std::pair<StringData, StringData> partitionBackward(StringData str, const char c
  *
  * foo=bar&baz=qux&...
  */
-StatusWith<MongoURI::OptionsMap> parseOptions(StringData options, StringData url) {
+MongoURI::OptionsMap parseOptions(StringData options, StringData url) {
     MongoURI::OptionsMap ret;
     if (options.empty()) {
         return ret;
     }
 
     if (options.find('?') != std::string::npos) {
-        return Status(ErrorCodes::FailedToParse,
-                      str::stream()
-                          << "URI Cannot Contain multiple questions marks for mongodb:// URL: "
-                          << url);
+        throw DBException(ErrorCodes::FailedToParse,
+                          str::stream()
+                              << "URI Cannot Contain multiple questions marks for mongodb:// URL: "
+                              << url);
     }
 
     const auto optionsStr = options.toString();
@@ -141,16 +144,16 @@ StatusWith<MongoURI::OptionsMap> parseOptions(StringData options, StringData url
          ++i) {
         const auto opt = boost::copy_range<std::string>(*i);
         if (opt.empty()) {
-            return Status(ErrorCodes::FailedToParse,
-                          str::stream()
-                              << "Missing a key/value pair in the options for mongodb:// URL: "
-                              << url);
+            throw DBException(ErrorCodes::FailedToParse,
+                              str::stream()
+                                  << "Missing a key/value pair in the options for mongodb:// URL: "
+                                  << url);
         }
 
         const auto kvPair = partitionForward(opt, '=');
         const auto keyRaw = kvPair.first;
         if (keyRaw.empty()) {
-            return Status(
+            throw DBException(
                 ErrorCodes::FailedToParse,
                 str::stream()
                     << "Missing a key for key/value pair in the options for mongodb:// URL: "
@@ -158,7 +161,7 @@ StatusWith<MongoURI::OptionsMap> parseOptions(StringData options, StringData url
         }
         const auto key = uriDecode(keyRaw);
         if (!key.isOK()) {
-            return Status(
+            throw DBException(
                 ErrorCodes::FailedToParse,
                 str::stream() << "Key '" << keyRaw
                               << "' in options cannot properly be URL decoded for mongodb:// URL: "
@@ -166,14 +169,14 @@ StatusWith<MongoURI::OptionsMap> parseOptions(StringData options, StringData url
         }
         const auto valRaw = kvPair.second;
         if (valRaw.empty()) {
-            return Status(ErrorCodes::FailedToParse,
-                          str::stream() << "Missing value for key '" << keyRaw
-                                        << "' in the options for mongodb:// URL: "
-                                        << url);
+            throw DBException(ErrorCodes::FailedToParse,
+                              str::stream() << "Missing value for key '" << keyRaw
+                                            << "' in the options for mongodb:// URL: "
+                                            << url);
         }
         const auto val = uriDecode(valRaw);
         if (!val.isOK()) {
-            return Status(
+            throw DBException(
                 ErrorCodes::FailedToParse,
                 str::stream() << "Value '" << valRaw << "' for key '" << keyRaw
                               << "' in options cannot properly be URL decoded for mongodb:// URL: "
@@ -186,20 +189,38 @@ StatusWith<MongoURI::OptionsMap> parseOptions(StringData options, StringData url
     return ret;
 }
 
+MongoURI::OptionsMap addTXTOptions(MongoURI::OptionsMap options,
+                                   const std::string& host,
+                                   const StringData url,
+                                   const bool isSeedlist) {
+    // If there is no seedlist mode, then don't add any TXT options.
+    if (!isSeedlist)
+        return options;
+
+    // Get all TXT records and parse them as options, adding them to the options set.
+    const auto txtRecords = dns::getTXTRecords(host);
+
+    for (const auto& record : txtRecords) {
+        auto txtOptions = parseOptions(record, url);
+        // Note that, `std::map` and `std::unordered_map` insert does not replace existing
+        // values -- this gives the desired behavior that user-specified values override TXT
+        // record specified values.
+        options.insert(begin(txtOptions), end(txtOptions));
+    }
+
+    return options;
+}
 }  // namespace
 
-StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
+MongoURI MongoURI::parseImpl(const std::string& url) {
     const StringData urlSD(url);
 
     // 1. Validate and remove the scheme prefix mongodb://
-    if (!urlSD.startsWith(kURIPrefix)) {
-        const auto cs_status = ConnectionString::parse(url);
-        if (!cs_status.isOK()) {
-            return cs_status.getStatus();
-        }
-        return MongoURI(cs_status.getValue());
+    const bool isSeedlist = urlSD.startsWith(kURISRVPrefix);
+    if (!(urlSD.startsWith(kURIPrefix) || isSeedlist)) {
+        return MongoURI(uassertStatusOK(ConnectionString::parse(url)));
     }
-    const auto uriWithoutPrefix = urlSD.substr(kURIPrefix.size());
+    const auto uriWithoutPrefix = urlSD.substr(urlSD.find("://") + 3);
 
     // 2. Split the string by the first, unescaped / (if any), yielding:
     // split[0]: User information and host identifers
@@ -211,14 +232,15 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
     // 2.b Make sure that there are no question marks in the left side of the /
     //     as any options after the ? must still have the / delimeter
     if (databaseAndOptions.empty() && userAndHostInfo.find('?') != std::string::npos) {
-        return Status(
+        throw DBException(
             ErrorCodes::FailedToParse,
             str::stream()
                 << "URI must contain slash delimeter between hosts and options for mongodb:// URL: "
                 << url);
     }
 
-    // 3. Split the user information and host identifiers string by the last, unescaped @, yielding:
+    // 3. Split the user information and host identifiers string by the last, unescaped @,
+    // yielding:
     // split[0]: User information
     // split[1]: Host identifiers;
     const auto userAndHost = partitionBackward(userAndHostInfo, '@');
@@ -237,18 +259,21 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
     };
 
     if (containsColonOrAt(usernameSD)) {
-        return Status(ErrorCodes::FailedToParse,
-                      str::stream() << "Username must be URL Encoded for mongodb:// URL: " << url);
+        throw DBException(ErrorCodes::FailedToParse,
+                          str::stream() << "Username must be URL Encoded for mongodb:// URL: "
+                                        << url);
     }
+
     if (containsColonOrAt(passwordSD)) {
-        return Status(ErrorCodes::FailedToParse,
-                      str::stream() << "Password must be URL Encoded for mongodb:// URL: " << url);
+        throw DBException(ErrorCodes::FailedToParse,
+                          str::stream() << "Password must be URL Encoded for mongodb:// URL: "
+                                        << url);
     }
 
     // Get the username and make sure it did not fail to decode
     const auto usernameWithStatus = uriDecode(usernameSD);
     if (!usernameWithStatus.isOK()) {
-        return Status(
+        throw DBException(
             ErrorCodes::FailedToParse,
             str::stream() << "Username cannot properly be URL decoded for mongodb:// URL: " << url);
     }
@@ -257,7 +282,7 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
     // Get the password and make sure it did not fail to decode
     const auto passwordWithStatus = uriDecode(passwordSD);
     if (!passwordWithStatus.isOK())
-        return Status(
+        throw DBException(
             ErrorCodes::FailedToParse,
             str::stream() << "Password cannot properly be URL decoded for mongodb:// URL: " << url);
     const auto password = passwordWithStatus.getValue();
@@ -271,7 +296,7 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
          ++i) {
         const auto hostWithStatus = uriDecode(boost::copy_range<std::string>(*i));
         if (!hostWithStatus.isOK()) {
-            return Status(
+            throw DBException(
                 ErrorCodes::FailedToParse,
                 str::stream() << "Host cannot properly be URL decoded for mongodb:// URL: " << url);
         }
@@ -282,23 +307,35 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
         }
 
         if ((host.find('/') != std::string::npos) && !StringData(host).endsWith(".sock")) {
-            return Status(
+            throw DBException(
                 ErrorCodes::FailedToParse,
                 str::stream() << "'" << host << "' in '" << url
                               << "' appears to be a unix socket, but does not end in '.sock'");
         }
 
-        const auto statusHostAndPort = HostAndPort::parse(host);
-        if (!statusHostAndPort.isOK()) {
-            return statusHostAndPort.getStatus();
-        }
-        servers.push_back(statusHostAndPort.getValue());
+        servers.push_back(uassertStatusOK(HostAndPort::parse(host)));
     }
     if (servers.empty()) {
-        return Status(ErrorCodes::FailedToParse, "No server(s) specified");
+        throw DBException(ErrorCodes::FailedToParse, "No server(s) specified");
     }
 
-    // 6. Split the auth database and connection options string by the first, unescaped ?, yielding:
+    const std::string canonicalHost = servers.front().host();
+    // If we're in seedlist mode, lookup the SRV record for `_mongodb._tcp` on the specified
+    // domain name.  Take that list of servers as the new list of servers.
+    if (isSeedlist) {
+        if (servers.size() > 1) {
+            throw DBException(ErrorCodes::FailedToParse,
+                              "Only a single server may be specified with a mongo+srv:// url.");
+        }
+        auto srvEntries = dns::lookupSRVRecords("_mongodb._tcp." + canonicalHost);
+        servers.clear();
+        std::transform(begin(srvEntries), end(srvEntries), back_inserter(servers), [](auto& srv) {
+            return HostAndPort(std::move(srv.host), srv.port);
+        });
+    }
+
+    // 6. Split the auth database and connection options string by the first, unescaped ?,
+    // yielding:
     // split[0] = auth database
     // split[1] = connection options
     const auto dbAndOpts = partitionForward(databaseAndOptions, '?');
@@ -306,10 +343,10 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
     const auto connectionOptions = dbAndOpts.second;
     const auto databaseWithStatus = uriDecode(databaseSD);
     if (!databaseWithStatus.isOK()) {
-        return Status(ErrorCodes::FailedToParse,
-                      str::stream()
-                          << "Database name cannot properly be URL decoded for mongodb:// URL: "
-                          << url);
+        throw DBException(ErrorCodes::FailedToParse,
+                          str::stream() << "Database name cannot properly be URL "
+                                           "decoded for mongodb:// URL: "
+                                        << url);
     }
     const auto database = databaseWithStatus.getValue();
 
@@ -320,35 +357,32 @@ StatusWith<MongoURI> MongoURI::parse(const std::string& url) {
     if (!database.empty() &&
         !NamespaceString::validDBName(database,
                                       NamespaceString::DollarInDbNameBehavior::Disallow)) {
-        return Status(ErrorCodes::FailedToParse,
-                      str::stream()
-                          << "Database name cannot have reserved characters for mongodb:// URL: "
-                          << url);
+        throw DBException(ErrorCodes::FailedToParse,
+                          str::stream() << "Database name cannot have reserved "
+                                           "characters for mongodb:// URL: "
+                                        << url);
     }
 
     // 8. Validate, split, and URL decode the connection options
-    const auto optsWith = parseOptions(connectionOptions, url);
-    if (!optsWith.isOK()) {
-        return optsWith.getStatus();
-    }
-    const auto options = optsWith.getValue();
+    auto options =
+        addTXTOptions(parseOptions(connectionOptions, url), canonicalHost, url, isSeedlist);
 
     // If a replica set option was specified, store it in the 'setName' field.
     const auto optIter = options.find("replicaSet");
     std::string setName;
-    if (optIter != options.end()) {
+    if (optIter != end(options)) {
         setName = optIter->second;
         invariant(!setName.empty());
     }
 
-    if ((servers.size() > 1) && setName.empty()) {
-        return Status(ErrorCodes::FailedToParse,
-                      "Cannot list multiple servers in URL without 'replicaSet' option");
-    }
-
     ConnectionString cs(
         setName.empty() ? ConnectionString::MASTER : ConnectionString::SET, servers, setName);
     return MongoURI(std::move(cs), username, password, database, std::move(options));
 }
 
+StatusWith<MongoURI> MongoURI::parse(const std::string& url) try {
+    return parseImpl(url);
+} catch (const std::exception&) {
+    return exceptionToStatus();
+}
 }  // namespace mongo
diff --git a/src/mongo/client/mongo_uri.h b/src/mongo/client/mongo_uri.h
index f7a7c4aeb81..11d948a526c 100644
--- a/src/mongo/client/mongo_uri.h
+++ b/src/mongo/client/mongo_uri.h
@@ -1,7 +1,7 @@
 /**
  *    Copyright (C) 2015 MongoDB Inc.
  *
- *    This program is free software: you can redistribute it and/or  modify
+ *    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.
  *
@@ -43,7 +43,6 @@
 #include "mongo/util/net/hostandport.h"
 
 namespace mongo {
-
 /**
  * Encode a string for embedding in a URI.
  * Replaces reserved bytes with %xx sequences.
@@ -51,6 +50,7 @@ namespace mongo {
  * Optionally allows passthrough characters to remain unescaped.
  */
 void uriEncode(std::ostream& ss, StringData str, StringData passthrough = ""_sd);
+
 inline std::string uriEncode(StringData str, StringData passthrough = ""_sd) {
     std::ostringstream ss;
     uriEncode(ss, str, passthrough);
@@ -66,9 +66,13 @@ StatusWith<std::string> uriDecode(StringData str);
 /**
  * MongoURI handles parsing of URIs for mongodb, and falls back to old-style
  * ConnectionString parsing. It's used primarily by the shell.
- * It parses URIs with the following format:
+ * It parses URIs with the following formats:
  *
  *    mongodb://[usr:pwd@]host1[:port1]...[,hostN[:portN]]][/[db][?options]]
+ *    mongodb+srv://[usr:pwd@]host[/[db][?options]]
+ *
+ * `mongodb+srv://` URIs will perform DNS SRV and TXT lookups and expand per the DNS Seedlist
+ * specification.
  *
  * While this format is generally RFC 3986 compliant, some exceptions do exist:
  *   1. The 'host' field, as defined by section 3.2.2 is expanded in the following ways:
@@ -96,6 +100,11 @@ StatusWith<std::string> uriDecode(StringData str);
  */
 class MongoURI {
 public:
+    // Note that, because this map is used for DNS TXT record injection on options, there is a
+    // requirement on its behavior for `insert`: insert must not replace or update existing values
+    // -- this gives the desired behavior that user-specified values override TXT record specified
+    // values.  `std::map` and `std::unordered_map` satisfy this requirement.  Make sure that
+    // whichever map type is used provides that guarantee.
     using OptionsMap = std::map<std::string, std::string>;
 
     static StatusWith<MongoURI> parse(const std::string& url);
@@ -140,20 +149,21 @@ public:
     // 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
     // be the single host you pass in.
-    MongoURI cloneURIForServer(const HostAndPort& hostAndPort) const {
-        return MongoURI(ConnectionString(hostAndPort), _user, _password, _database, _options);
+    MongoURI cloneURIForServer(HostAndPort hostAndPort) const {
+        return MongoURI(
+            ConnectionString(std::move(hostAndPort)), _user, _password, _database, _options);
     }
 
     ConnectionString::ConnectionType type() const {
         return _connectString.type();
     }
 
-    explicit MongoURI(const ConnectionString connectString)
-        : _connectString(std::move(connectString)){};
+    explicit MongoURI(const ConnectionString& connectString) : _connectString(connectString){};
 
     MongoURI() = default;
 
     friend std::ostream& operator<<(std::ostream&, const MongoURI&);
+
     friend StringBuilder& operator<<(StringBuilder&, const MongoURI&);
 
 private:
@@ -166,10 +176,12 @@ private:
           _user(user),
           _password(password),
           _database(database),
-          _options(std::move(options)){};
+          _options(std::move(options)) {}
 
     BSONObj _makeAuthObjFromOptions(int maxWireVersion) const;
 
+    static MongoURI parseImpl(const std::string& url);
+
     ConnectionString _connectString;
     std::string _user;
     std::string _password;
@@ -178,13 +190,10 @@ private:
 };
 
 inline std::ostream& operator<<(std::ostream& ss, const MongoURI& uri) {
-    ss << uri._connectString;
-    return ss;
+    return ss << uri._connectString;
 }
 
 inline StringBuilder& operator<<(StringBuilder& sb, const MongoURI& uri) {
-    sb << uri._connectString;
-    return sb;
+    return sb << uri._connectString;
 }
-
 }  // namespace mongo
diff --git a/src/mongo/client/mongo_uri_test.cpp b/src/mongo/client/mongo_uri_test.cpp
index 00edcb110f4..5153452f9ec 100644
--- a/src/mongo/client/mongo_uri_test.cpp
+++ b/src/mongo/client/mongo_uri_test.cpp
@@ -1,7 +1,7 @@
 /**
  *    Copyright (C) 2009-2015 MongoDB Inc.
  *
- *    This program is free software: you can redistribute it and/or  modify
+ *    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.
  *
@@ -506,8 +506,8 @@ TEST(MongoURI, CloneURIForServer) {
 /**
  * These tests come from the Mongo Uri Specifications for the drivers found at:
  * https://github.com/mongodb/specifications/tree/master/source/connection-string/tests
- * They have been slighly altered as the Drivers specification is slighly different
- * from the server specification.
+ * They have been altered as the Drivers specification is somewhat different from the shell
+ * implementation.
  */
 TEST(MongoURI, specTests) {
     const std::string files[] = {
@@ -599,4 +599,156 @@ TEST(MongoURI, specTests) {
     }
 }
 
+TEST(MongoURI, srvRecordTest) {
+    using namespace mongo;
+    const struct {
+        std::string uri;
+        std::string user;
+        std::string password;
+        std::string database;
+        std::vector<HostAndPort> hosts;
+        std::map<std::string, std::string> options;
+    } tests[] = {
+        // Test some non-SRV URIs to make sure that they do not perform expansions
+        {"mongodb://test1.test.build.10gen.cc:12345/",
+         "",
+         "",
+         "",
+         {{"test1.test.build.10gen.cc", 12345}},
+         {}},
+        {"mongodb://test6.test.build.10gen.cc:12345/",
+         "",
+         "",
+         "",
+         {{"test6.test.build.10gen.cc", 12345}},
+         {}},
+
+        // Test a sample URI against each provided testing DNS entry
+        {"mongodb+srv://test1.test.build.10gen.cc/",
+         "",
+         "",
+         "",
+         {{"localhost.build.10gen.cc.", 27017}, {"localhost.build.10gen.cc.", 27018}},
+         {}},
+
+        {"mongodb+srv://user:password@test2.test.build.10gen.cc/"
+         "database?someOption=someValue&someOtherOption=someOtherValue",
+         "user",
+         "password",
+         "database",
+         {{"localhost.build.10gen.cc.", 27018}, {"localhost.build.10gen.cc.", 27019}},
+         {{"someOption", "someValue"}, {"someOtherOption", "someOtherValue"}}},
+
+
+        {"mongodb+srv://user:password@test3.test.build.10gen.cc/"
+         "database?someOption=someValue&someOtherOption=someOtherValue",
+         "user",
+         "password",
+         "database",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"someOption", "someValue"}, {"someOtherOption", "someOtherValue"}}},
+
+
+        {"mongodb+srv://user:password@test5.test.build.10gen.cc/"
+         "database?someOption=someValue&someOtherOption=someOtherValue",
+         "user",
+         "password",
+         "database",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"someOption", "someValue"},
+          {"someOtherOption", "someOtherValue"},
+          {"connectTimeoutMS", "300000"},
+          {"socketTimeoutMS", "300000"}}},
+
+        {"mongodb+srv://user:password@test5.test.build.10gen.cc/"
+         "database?someOption=someValue&socketTimeoutMS=100&someOtherOption=someOtherValue",
+         "user",
+         "password",
+         "database",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"someOption", "someValue"},
+          {"someOtherOption", "someOtherValue"},
+          {"connectTimeoutMS", "300000"},
+          {"socketTimeoutMS", "100"}}},
+
+        {"mongodb+srv://test6.test.build.10gen.cc/",
+         "",
+         "",
+         "",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"connectTimeoutMS", "200000"}, {"socketTimeoutMS", "200000"}}},
+
+        {"mongodb+srv://test6.test.build.10gen.cc/database",
+         "",
+         "",
+         "database",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"connectTimeoutMS", "200000"}, {"socketTimeoutMS", "200000"}}},
+
+        {"mongodb+srv://test6.test.build.10gen.cc/?connectTimeoutMS=300000",
+         "",
+         "",
+         "",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"connectTimeoutMS", "300000"}, {"socketTimeoutMS", "200000"}}},
+
+        {"mongodb+srv://test6.test.build.10gen.cc/?irrelevantOption=irrelevantValue",
+         "",
+         "",
+         "",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"connectTimeoutMS", "200000"},
+          {"socketTimeoutMS", "200000"},
+          {"irrelevantOption", "irrelevantValue"}}},
+
+
+        {"mongodb+srv://test6.test.build.10gen.cc/"
+         "?irrelevantOption=irrelevantValue&connectTimeoutMS=300000",
+         "",
+         "",
+         "",
+         {{"localhost.build.10gen.cc.", 27017}},
+         {{"connectTimeoutMS", "300000"},
+          {"socketTimeoutMS", "200000"},
+          {"irrelevantOption", "irrelevantValue"}}},
+    };
+
+    for (const auto& test : tests) {
+        auto rs = MongoURI::parse(test.uri);
+        ASSERT_OK(rs.getStatus());
+        auto rv = rs.getValue();
+        ASSERT_EQ(rv.getUser(), test.user);
+        ASSERT_EQ(rv.getPassword(), test.password);
+        ASSERT_EQ(rv.getDatabase(), test.database);
+        std::vector<std::pair<std::string, std::string>> options(begin(rv.getOptions()),
+                                                                 end(rv.getOptions()));
+        std::sort(begin(options), end(options));
+        std::vector<std::pair<std::string, std::string>> expectedOptions(begin(test.options),
+                                                                         end(test.options));
+        std::sort(begin(expectedOptions), end(expectedOptions));
+
+        for (std::size_t i = 0; i < std::min(options.size(), expectedOptions.size()); ++i) {
+            if (options[i] != expectedOptions[i]) {
+                mongo::unittest::log() << "Option: \"" << options[i].first << "="
+                                       << options[i].second << "\" doesn't equal: \""
+                                       << expectedOptions[i].first << "="
+                                       << expectedOptions[i].second << "\"" << std::endl;
+                std::cerr << "Failing URI: \"" << test.uri << "\"" << std::endl;
+                ASSERT(false);
+            }
+        }
+        ASSERT_EQ(options.size(), expectedOptions.size());
+
+        std::vector<HostAndPort> hosts(begin(rv.getServers()), end(rv.getServers()));
+        std::sort(begin(hosts), end(hosts));
+        auto expectedHosts = test.hosts;
+        std::sort(begin(expectedHosts), end(expectedHosts));
+
+        for (std::size_t i = 0; i < std::min(hosts.size(), expectedHosts.size()); ++i) {
+            ASSERT_EQ(hosts[i], expectedHosts[i]);
+        }
+        ASSERT_TRUE(hosts.size() == expectedHosts.size());
+    }
+}
+
 }  // namespace
diff --git a/src/mongo/client/mongo_uri_tests/mongo-uri-host-identifiers.json b/src/mongo/client/mongo_uri_tests/mongo-uri-host-identifiers.json
index 8a1fda580a8..5af3797ccdb 100644
--- a/src/mongo/client/mongo_uri_tests/mongo-uri-host-identifiers.json
+++ b/src/mongo/client/mongo_uri_tests/mongo-uri-host-identifiers.json
@@ -108,7 +108,7 @@
     {
       "description": "Multiple hosts (mixed formats)",
       "uri": "mongodb://127.0.0.1,[::1]:27018,example.com:27019",
-      "valid": false,
+      "valid": true,
       "warning": false,
       "hosts": [
         {
@@ -160,7 +160,7 @@
     {
       "description": "UTF-8 hosts",
       "uri": "mongodb://bücher.example.com,umläut.example.com/",
-      "valid": false,
+      "valid": true,
       "warning": false,
       "hosts": [
         {
@@ -200,4 +200,4 @@
       }
     }
   ]
-}
\ No newline at end of file
+}
diff --git a/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-absolute.json b/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-absolute.json
index d167c315bbc..f4f78883298 100644
--- a/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-absolute.json
+++ b/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-absolute.json
@@ -62,7 +62,7 @@
             ],
             "options": null,
             "uri": "mongodb://%2Ftmp%2Fmongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -82,7 +82,7 @@
             ],
             "options": null,
             "uri": "mongodb://127.0.0.1:27017,%2Ftmp%2Fmongodb-27017.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -102,7 +102,7 @@
             ],
             "options": null,
             "uri": "mongodb://mongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -260,7 +260,7 @@
             ],
             "options": null,
             "uri": "mongodb://%2Ftmp%2Fmongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock/admin",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -312,7 +312,7 @@
                 "w": 1
             },
             "uri": "mongodb://bob:bar@%2Ftmp%2Fmongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock/admin?w=1",
-            "valid": false,
+            "valid": true,
             "warning": false
         }, 
         {
diff --git a/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-relative.json b/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-relative.json
index 8da45c4e1b9..a2d737ba72a 100644
--- a/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-relative.json
+++ b/src/mongo/client/mongo_uri_tests/mongo-uri-unix-sockets-relative.json
@@ -62,7 +62,7 @@
             ],
             "options": null,
             "uri": "mongodb://rel%2Fmongodb-27017.sock,rel%2Fmongodb-27018.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -104,7 +104,7 @@
             ],
             "options": null,
             "uri": "mongodb://rel%2Fmongodb-27017.sock,%2Ftmp%2Fmongodb-27018.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -146,7 +146,7 @@
             ],
             "options": null,
             "uri": "mongodb://127.0.0.1:27017,rel%2Fmongodb-27017.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -188,7 +188,7 @@
             ],
             "options": null,
             "uri": "mongodb://mongodb-27017.sock,rel%2Fmongodb-27018.sock",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -302,7 +302,7 @@
             ],
             "options": null,
             "uri": "mongodb://rel%2Fmongodb-27017.sock,rel%2Fmongodb-27018.sock/admin",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -352,7 +352,7 @@
             ],
             "options": null,
             "uri": "mongodb://rel%2Fmongodb-27017.sock,rel%2Fmongodb-27018.sock/admin",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -404,7 +404,7 @@
                 "w": 1
             },
             "uri": "mongodb://bob:bar@rel%2Fmongodb-27017.sock,rel%2Fmongodb-27018.sock/admin?w=1",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
diff --git a/src/mongo/client/mongo_uri_tests/mongo-uri-valid-auth.json b/src/mongo/client/mongo_uri_tests/mongo-uri-valid-auth.json
index a44236e7b62..68228c6ddec 100644
--- a/src/mongo/client/mongo_uri_tests/mongo-uri-valid-auth.json
+++ b/src/mongo/client/mongo_uri_tests/mongo-uri-valid-auth.json
@@ -135,7 +135,7 @@
             ],
             "options": null,
             "uri": "mongodb://alice:secret@127.0.0.1,example.com:27018",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {
@@ -159,7 +159,7 @@
             ],
             "options": null,
             "uri": "mongodb://alice:secret@example.com,[::1]:27019/admin",
-            "valid": false,
+            "valid": true,
             "warning": false
         },
         {