SERVER-19420 implement connection hook API in NetworkInterfaceASIO

13 files changed, 658 insertions, 190 deletions

diff --git a/src/mongo/executor/SConscript b/src/mongo/executor/SConscript
index 22e895e1f5d..3d3d6b05f7a 100644
--- a/src/mongo/executor/SConscript
+++ b/src/mongo/executor/SConscript
@@ -72,7 +72,6 @@ env.Library(target='network_test_env',
 env.Library(
     target='network_interface_asio',
     source=[
-        'async_mock_stream_factory.cpp',
         'async_secure_stream.cpp',
         'async_secure_stream_factory.cpp',
         'async_stream.cpp',
@@ -96,6 +95,7 @@ env.Library(
 env.CppUnitTest(
     target='network_interface_asio_test',
     source=[
+        'async_mock_stream_factory.cpp',
         'network_interface_asio_test.cpp',
     ],
     LIBDEPS=[
diff --git a/src/mongo/executor/async_mock_stream_factory.cpp b/src/mongo/executor/async_mock_stream_factory.cpp
index 88229496110..ef007870176 100644
--- a/src/mongo/executor/async_mock_stream_factory.cpp
+++ b/src/mongo/executor/async_mock_stream_factory.cpp
@@ -32,12 +32,18 @@
 
 #include "mongo/executor/async_mock_stream_factory.h"
 
+#include <exception>
 #include <iterator>
 #include <system_error>
 
+#include "mongo/rpc/command_reply_builder.h"
+#include "mongo/rpc/factory.h"
+#include "mongo/rpc/legacy_reply_builder.h"
+#include "mongo/rpc/request_interface.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/log.h"
+#include "mongo/util/net/message.h"
 
 namespace mongo {
 namespace executor {
@@ -86,9 +92,9 @@ void AsyncMockStreamFactory::MockStream::connect(asio::ip::tcp::resolver::iterat
                                                  ConnectHandler&& connectHandler) {
     {
         stdx::unique_lock<stdx::mutex> lk(_mutex);
-        log() << "connect() for: " << _target;
 
-        _block_inlock(&lk);
+        // Block before returning from connect.
+        _block_inlock(kBlockedBeforeConnect, &lk);
     }
     _io_service->post([connectHandler, endpoints] { connectHandler(std::error_code()); });
 }
@@ -96,15 +102,13 @@ void AsyncMockStreamFactory::MockStream::connect(asio::ip::tcp::resolver::iterat
 void AsyncMockStreamFactory::MockStream::write(asio::const_buffer buf,
                                                StreamHandler&& writeHandler) {
     stdx::unique_lock<stdx::mutex> lk(_mutex);
-    log() << "write() for: " << _target;
-
 
     auto begin = asio::buffer_cast<const uint8_t*>(buf);
     auto size = asio::buffer_size(buf);
     _writeQueue.push({begin, begin + size});
 
     // Block after data is written.
-    _block_inlock(&lk);
+    _block_inlock(kBlockedAfterWrite, &lk);
 
     lk.unlock();
     _io_service->post([writeHandler, size] { writeHandler(std::error_code(), size); });
@@ -113,10 +117,8 @@ void AsyncMockStreamFactory::MockStream::write(asio::const_buffer buf,
 void AsyncMockStreamFactory::MockStream::read(asio::mutable_buffer buf,
                                               StreamHandler&& readHandler) {
     stdx::unique_lock<stdx::mutex> lk(_mutex);
-    log() << "read() for: " << _target;
-
     // Block before data is read.
-    _block_inlock(&lk);
+    _block_inlock(kBlockedBeforeRead, &lk);
 
     auto nextRead = std::move(_readQueue.front());
     _readQueue.pop();
@@ -138,26 +140,26 @@ void AsyncMockStreamFactory::MockStream::read(asio::mutable_buffer buf,
 
 void AsyncMockStreamFactory::MockStream::pushRead(std::vector<uint8_t> toRead) {
     stdx::unique_lock<stdx::mutex> lk(_mutex);
-    invariant(_blocked);
+    invariant(_state != kRunning);
     _readQueue.emplace(std::move(toRead));
 }
 
 std::vector<uint8_t> AsyncMockStreamFactory::MockStream::popWrite() {
     stdx::unique_lock<stdx::mutex> lk(_mutex);
-    invariant(_blocked);
+    invariant(_state != kRunning);
     auto nextWrite = std::move(_writeQueue.front());
     _writeQueue.pop();
     return nextWrite;
 }
 
-void AsyncMockStreamFactory::MockStream::_block_inlock(stdx::unique_lock<stdx::mutex>* lk) {
-    log() << "blocking in stream for: " << _target;
-    invariant(!_blocked);
-    _blocked = true;
+void AsyncMockStreamFactory::MockStream::_block_inlock(StreamState state,
+                                                       stdx::unique_lock<stdx::mutex>* lk) {
+    invariant(_state == kRunning);
+    _state = state;
     lk->unlock();
     _cv.notify_one();
     lk->lock();
-    _cv.wait(*lk, [this]() { return !_blocked; });
+    _cv.wait(*lk, [this]() { return _state == kRunning; });
 }
 
 void AsyncMockStreamFactory::MockStream::unblock() {
@@ -166,18 +168,79 @@ void AsyncMockStreamFactory::MockStream::unblock() {
 }
 
 void AsyncMockStreamFactory::MockStream::_unblock_inlock(stdx::unique_lock<stdx::mutex>* lk) {
-    log() << "unblocking stream for: " << _target;
-    invariant(_blocked);
-    _blocked = false;
+    invariant(_state != kRunning);
+    _state = kRunning;
     lk->unlock();
     _cv.notify_one();
     lk->lock();
 }
 
-void AsyncMockStreamFactory::MockStream::waitUntilBlocked() {
+auto AsyncMockStreamFactory::MockStream::waitUntilBlocked() -> StreamState {
     stdx::unique_lock<stdx::mutex> lk(_mutex);
-    log() << "waiting until stream for " << _target << " has blocked";
-    _cv.wait(lk, [this]() { return _blocked; });
+    _cv.wait(lk, [this]() { return _state != kRunning; });
+    return _state;
+}
+
+HostAndPort AsyncMockStreamFactory::MockStream::target() {
+    return _target;
+}
+
+void AsyncMockStreamFactory::MockStream::simulateServer(
+    rpc::Protocol proto,
+    const stdx::function<RemoteCommandResponse(RemoteCommandRequest)> replyFunc) {
+    std::exception_ptr ex;
+    uint32_t messageId = 0;
+
+    RemoteCommandResponse resp;
+    {
+        WriteEvent write{this};
+
+        std::vector<uint8_t> messageData = popWrite();
+        Message msg(messageData.data(), false);
+
+        auto parsedRequest = rpc::makeRequest(&msg);
+        ASSERT(parsedRequest->getProtocol() == proto);
+
+        RemoteCommandRequest rcr(target(), *parsedRequest);
+
+        messageId = msg.header().getId();
+
+        // So we can allow ASSERTs in replyFunc, we capture any exceptions, but rethrow
+        // them later to prevent deadlock
+        try {
+            resp = replyFunc(std::move(rcr));
+        } catch (...) {
+            ex = std::current_exception();
+        }
+    }
+
+    auto replyBuilder = rpc::makeReplyBuilder(proto);
+    replyBuilder->setMetadata(resp.metadata);
+    replyBuilder->setCommandReply(resp.data);
+
+    auto replyMsg = replyBuilder->done();
+    replyMsg->header().setResponseTo(messageId);
+
+    {
+        // The first read will be for the header.
+        ReadEvent read{this};
+        auto hdrBytes = reinterpret_cast<const uint8_t*>(replyMsg->header().view2ptr());
+        pushRead({hdrBytes, hdrBytes + sizeof(MSGHEADER::Value)});
+    }
+
+    {
+        // The second read will be for the message data.
+        ReadEvent read{this};
+        auto dataBytes = reinterpret_cast<const uint8_t*>(replyMsg->buf());
+        auto pastHeader = dataBytes;
+        std::advance(pastHeader, sizeof(MSGHEADER::Value));
+        pushRead({pastHeader, dataBytes + static_cast<std::size_t>(replyMsg->size())});
+    }
+
+    if (ex) {
+        // Rethrow ASSERTS after the NIA completes it's Write-Read-Read sequence.
+        std::rethrow_exception(ex);
+    }
 }
 
 }  // namespace executor
diff --git a/src/mongo/executor/async_mock_stream_factory.h b/src/mongo/executor/async_mock_stream_factory.h
index 0948b7b13cd..856f12e7187 100644
--- a/src/mongo/executor/async_mock_stream_factory.h
+++ b/src/mongo/executor/async_mock_stream_factory.h
@@ -36,8 +36,13 @@
 
 #include "mongo/executor/async_stream_factory_interface.h"
 #include "mongo/executor/async_stream_interface.h"
-#include "mongo/stdx/mutex.h"
+#include "mongo/executor/remote_command_request.h"
+#include "mongo/executor/remote_command_response.h"
+#include "mongo/rpc/protocol.h"
 #include "mongo/stdx/condition_variable.h"
+#include "mongo/stdx/functional.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/unittest/unittest.h"
 #include "mongo/util/net/hostandport.h"
 
 namespace mongo {
@@ -57,6 +62,15 @@ public:
         MockStream(asio::io_service* io_service,
                    AsyncMockStreamFactory* factory,
                    const HostAndPort& target);
+
+        // Use unscoped enum so we can specialize on it
+        enum StreamState {
+            kRunning,
+            kBlockedBeforeConnect,
+            kBlockedBeforeRead,
+            kBlockedAfterWrite,
+        };
+
         ~MockStream();
 
         void connect(asio::ip::tcp::resolver::iterator endpoints,
@@ -64,27 +78,32 @@ public:
         void write(asio::const_buffer buf, StreamHandler&& writeHandler) override;
         void read(asio::mutable_buffer buf, StreamHandler&& readHandler) override;
 
-        void waitUntilBlocked();
+        HostAndPort target();
+
+        StreamState waitUntilBlocked();
 
         std::vector<uint8_t> popWrite();
         void pushRead(std::vector<uint8_t> toRead);
 
         void unblock();
 
+        void simulateServer(
+            rpc::Protocol proto,
+            const stdx::function<RemoteCommandResponse(RemoteCommandRequest)> replyFunc);
+
     private:
         void _unblock_inlock(stdx::unique_lock<stdx::mutex>* lk);
-        void _block_inlock(stdx::unique_lock<stdx::mutex>* lk);
+        void _block_inlock(StreamState state, stdx::unique_lock<stdx::mutex>* lk);
 
         asio::io_service* _io_service;
 
         AsyncMockStreamFactory* _factory;
         HostAndPort _target;
 
-
         stdx::mutex _mutex;
 
         stdx::condition_variable _cv;
-        bool _blocked{false};
+        StreamState _state{kRunning};
 
         std::queue<std::vector<uint8_t>> _readQueue;
         std::queue<std::vector<uint8_t>> _writeQueue;
@@ -102,5 +121,33 @@ private:
     std::unordered_map<HostAndPort, MockStream*> _streams;
 };
 
+template <int EventType>
+class StreamEvent {
+public:
+    StreamEvent(AsyncMockStreamFactory::MockStream* stream) : _stream(stream) {
+        ASSERT(stream->waitUntilBlocked() == EventType);
+    }
+
+    void skip() {
+        _stream->unblock();
+        skipped = true;
+    }
+
+    ~StreamEvent() {
+        if (!skipped) {
+            skip();
+        }
+    }
+
+private:
+    bool skipped = false;
+    AsyncMockStreamFactory::MockStream* _stream = nullptr;
+};
+
+using ReadEvent = StreamEvent<AsyncMockStreamFactory::MockStream::StreamState::kBlockedBeforeRead>;
+using WriteEvent = StreamEvent<AsyncMockStreamFactory::MockStream::StreamState::kBlockedAfterWrite>;
+using ConnectEvent =
+    StreamEvent<AsyncMockStreamFactory::MockStream::StreamState::kBlockedBeforeConnect>;
+
 }  // namespace executor
 }  // namespace mongo
diff --git a/src/mongo/executor/network_interface_asio.cpp b/src/mongo/executor/network_interface_asio.cpp
index b122d76ab87..4b40543a53b 100644
--- a/src/mongo/executor/network_interface_asio.cpp
+++ b/src/mongo/executor/network_interface_asio.cpp
@@ -48,7 +48,13 @@ namespace executor {
 
 NetworkInterfaceASIO::NetworkInterfaceASIO(
     std::unique_ptr<AsyncStreamFactoryInterface> streamFactory)
+    : NetworkInterfaceASIO(std::move(streamFactory), nullptr) {}
+
+NetworkInterfaceASIO::NetworkInterfaceASIO(
+    std::unique_ptr<AsyncStreamFactoryInterface> streamFactory,
+    std::unique_ptr<NetworkConnectionHook> networkConnectionHook)
     : _io_service(),
+      _hook(std::move(networkConnectionHook)),
       _resolver(_io_service),
       _state(State::kReady),
       _streamFactory(std::move(streamFactory)),
diff --git a/src/mongo/executor/network_interface_asio.h b/src/mongo/executor/network_interface_asio.h
index 724a16d7c9a..7cd1a2f2993 100644
--- a/src/mongo/executor/network_interface_asio.h
+++ b/src/mongo/executor/network_interface_asio.h
@@ -38,6 +38,7 @@
 
 #include "mongo/base/status.h"
 #include "mongo/base/system_error.h"
+#include "mongo/executor/network_connection_hook.h"
 #include "mongo/executor/network_interface.h"
 #include "mongo/executor/remote_command_request.h"
 #include "mongo/executor/remote_command_response.h"
@@ -54,7 +55,6 @@ namespace executor {
 
 class AsyncStreamFactoryInterface;
 class AsyncStreamInterface;
-class NetworkConnectionHook;
 
 /**
  * Implementation of the replication system's network interface using Christopher
@@ -62,6 +62,8 @@ class NetworkConnectionHook;
  */
 class NetworkInterfaceASIO final : public NetworkInterface {
 public:
+    NetworkInterfaceASIO(std::unique_ptr<AsyncStreamFactoryInterface> streamFactory,
+                         std::unique_ptr<NetworkConnectionHook> networkConnectionHook);
     NetworkInterfaceASIO(std::unique_ptr<AsyncStreamFactoryInterface> streamFactory);
     std::string getDiagnosticString() override;
     std::string getHostName() override;
@@ -239,6 +241,7 @@ private:
     void _setupSocket(AsyncOp* op, asio::ip::tcp::resolver::iterator endpoints);
 
     void _runIsMaster(AsyncOp* op);
+    void _runConnectionHook(AsyncOp* op);
     void _authenticate(AsyncOp* op);
 
     // Communication state machine
@@ -254,6 +257,8 @@ private:
     asio::io_service _io_service;
     stdx::thread _serviceRunner;
 
+    std::unique_ptr<NetworkConnectionHook> _hook;
+
     asio::ip::tcp::resolver _resolver;
 
     std::atomic<State> _state;
diff --git a/src/mongo/executor/network_interface_asio_auth.cpp b/src/mongo/executor/network_interface_asio_auth.cpp
index a6f1fdcfa38..f239389408a 100644
--- a/src/mongo/executor/network_interface_asio_auth.cpp
+++ b/src/mongo/executor/network_interface_asio_auth.cpp
@@ -62,33 +62,40 @@ void NetworkInterfaceASIO::_runIsMaster(AsyncOp* op) {
 
     // Callback to parse protocol information out of received ismaster response
     auto parseIsMaster = [this, op]() {
-        try {
-            auto commandReply = rpc::makeReply(&(op->command().toRecv()));
-            BSONObj isMasterReply = commandReply->getCommandReply();
 
-            auto protocolSet = rpc::parseProtocolSetFromIsMasterReply(isMasterReply);
-            if (!protocolSet.isOK())
-                return _completeOperation(op, protocolSet.getStatus());
-
-            op->connection().setServerProtocols(protocolSet.getValue());
+        auto swCommandReply = op->command().response(rpc::Protocol::kOpQuery, now());
+        if (!swCommandReply.isOK()) {
+            return _completeOperation(op, swCommandReply.getStatus());
+        }
 
-            // Set the operation protocol
-            auto negotiatedProtocol = rpc::negotiate(op->connection().serverProtocols(),
-                                                     op->connection().clientProtocols());
+        auto commandReply = std::move(swCommandReply.getValue());
 
-            if (!negotiatedProtocol.isOK()) {
-                return _completeOperation(op, negotiatedProtocol.getStatus());
+        if (_hook) {
+            // Run the validation hook.
+            auto validHost = _hook->validateHost(op->request().target, commandReply);
+            if (!validHost.isOK()) {
+                return _completeOperation(op, validHost);
             }
+        }
+
+        auto protocolSet = rpc::parseProtocolSetFromIsMasterReply(commandReply.data);
+        if (!protocolSet.isOK())
+            return _completeOperation(op, protocolSet.getStatus());
 
-            op->setOperationProtocol(negotiatedProtocol.getValue());
+        op->connection().setServerProtocols(protocolSet.getValue());
 
-            // Advance the state machine
-            return _authenticate(op);
+        // Set the operation protocol
+        auto negotiatedProtocol =
+            rpc::negotiate(op->connection().serverProtocols(), op->connection().clientProtocols());
 
-        } catch (...) {
-            // makeReply will throw if the reply was invalid.
-            return _completeOperation(op, exceptionToStatus());
+        if (!negotiatedProtocol.isOK()) {
+            return _completeOperation(op, negotiatedProtocol.getStatus());
         }
+
+        op->setOperationProtocol(negotiatedProtocol.getValue());
+
+        return _authenticate(op);
+
     };
 
     _asyncRunCommand(&cmd,
@@ -105,7 +112,7 @@ void NetworkInterfaceASIO::_authenticate(AsyncOp* op) {
     // This check is sufficient to see if auth is enabled on the system,
     // and avoids creating dependencies on deeper, less accessible auth code.
     if (!isInternalAuthSet()) {
-        return asio::post(_io_service, [this, op]() { _beginCommunication(op); });
+        return _runConnectionHook(op);
     }
 
     // We will only have a valid clientName if SSL is enabled.
@@ -136,7 +143,7 @@ void NetworkInterfaceASIO::_authenticate(AsyncOp* op) {
     auto authHook = [this, op](auth::AuthResponse response) {
         if (!response.isOK())
             return _completeOperation(op, response);
-        return _beginCommunication(op);
+        return _runConnectionHook(op);
     };
 
     auto params = getInternalUserAuthParamsWithFallback();
diff --git a/src/mongo/executor/network_interface_asio_command.cpp b/src/mongo/executor/network_interface_asio_command.cpp
index 35237245ea2..fa1a560521b 100644
--- a/src/mongo/executor/network_interface_asio_command.cpp
+++ b/src/mongo/executor/network_interface_asio_command.cpp
@@ -41,6 +41,7 @@
 #include "mongo/rpc/factory.h"
 #include "mongo/rpc/protocol.h"
 #include "mongo/rpc/reply_interface.h"
+#include "mongo/rpc/request_builder_interface.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/log.h"
@@ -271,5 +272,48 @@ void NetworkInterfaceASIO::_asyncRunCommand(AsyncCommand* cmd, NetworkOpHandler
     asyncSendMessage(cmd->conn().stream(), &cmd->toSend(), std::move(sendMessageCallback));
 }
 
+void NetworkInterfaceASIO::_runConnectionHook(AsyncOp* op) {
+    if (!_hook) {
+        return _beginCommunication(op);
+    }
+
+    auto swOptionalRequest = _hook->makeRequest(op->request().target);
+
+    if (!swOptionalRequest.isOK()) {
+        return _completeOperation(op, swOptionalRequest.getStatus());
+    }
+
+    auto optionalRequest = std::move(swOptionalRequest.getValue());
+
+    if (optionalRequest == boost::none) {
+        return _beginCommunication(op);
+    }
+
+    auto& cmd = op->beginCommand(*optionalRequest, op->operationProtocol(), now());
+
+    auto finishHook = [this, op]() {
+        auto response = op->command().response(op->operationProtocol(), now());
+
+        if (!response.isOK()) {
+            return _completeOperation(op, response.getStatus());
+        }
+
+        auto handleStatus =
+            _hook->handleReply(op->request().target, std::move(response.getValue()));
+
+        if (!handleStatus.isOK()) {
+            return _completeOperation(op, handleStatus);
+        }
+
+        return _beginCommunication(op);
+    };
+
+    return _asyncRunCommand(&cmd,
+                            [this, op, finishHook](std::error_code ec, std::size_t bytes) {
+                                _validateAndRun(op, ec, finishHook);
+                            });
+}
+
+
 }  // namespace executor
 }  // namespace mongo
diff --git a/src/mongo/executor/network_interface_asio_test.cpp b/src/mongo/executor/network_interface_asio_test.cpp
index a1aeb324eab..da3cde07874 100644
--- a/src/mongo/executor/network_interface_asio_test.cpp
+++ b/src/mongo/executor/network_interface_asio_test.cpp
@@ -30,15 +30,15 @@
 
 #include "mongo/platform/basic.h"
 
+#include <boost/optional.hpp>
+
+#include "mongo/base/status_with.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/wire_version.h"
 #include "mongo/executor/async_mock_stream_factory.h"
 #include "mongo/executor/network_interface_asio.h"
-#include "mongo/rpc/command_reply_builder.h"
-#include "mongo/rpc/factory.h"
+#include "mongo/executor/test_network_connection_hook.h"
 #include "mongo/rpc/legacy_reply_builder.h"
-#include "mongo/rpc/protocol.h"
-#include "mongo/rpc/request_interface.h"
 #include "mongo/stdx/future.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/unittest.h"
@@ -49,6 +49,8 @@ namespace mongo {
 namespace executor {
 namespace {
 
+HostAndPort testHost{"localhost", 20000};
+
 class NetworkInterfaceASIOTest : public mongo::unittest::Test {
 public:
     void setUp() override {
@@ -73,7 +75,11 @@ public:
         return *_streamFactory;
     }
 
-private:
+    void simulateServerReply(AsyncMockStreamFactory::MockStream* stream,
+                             rpc::Protocol proto,
+                             const stdx::function<RemoteCommandResponse(RemoteCommandRequest)>) {}
+
+protected:
     AsyncMockStreamFactory* _streamFactory;
     std::unique_ptr<NetworkInterfaceASIO> _net;
 };
@@ -104,124 +110,339 @@ TEST_F(NetworkInterfaceASIOTest, StartCommand) {
     auto stream = streamFactory().blockUntilStreamExists(testHost);
 
     // Allow stream to connect.
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-    }
-
-    log() << "connected";
-
-    uint32_t isMasterMsgId = 0;
-
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-
-        log() << "NIA blocked after writing isMaster request";
-
-        // Check that an isMaster has been run on the stream
-        std::vector<uint8_t> messageData = stream->popWrite();
-        Message msg(messageData.data(), false);
-
-        auto request = rpc::makeRequest(&msg);
-
-        ASSERT_EQ(request->getCommandName(), "isMaster");
-        ASSERT_EQ(request->getDatabase(), "admin");
-
-        isMasterMsgId = msg.header().getId();
-
-        // Check that we used OP_QUERY.
-        ASSERT(request->getProtocol() == rpc::Protocol::kOpQuery);
-    }
-
-    rpc::LegacyReplyBuilder replyBuilder;
-    replyBuilder.setMetadata(BSONObj());
-    replyBuilder.setCommandReply(BSON("minWireVersion" << mongo::minWireVersion << "maxWireVersion"
-                                                       << mongo::maxWireVersion));
-    auto replyMsg = replyBuilder.done();
-    replyMsg->header().setResponseTo(isMasterMsgId);
-
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-
-        log() << "NIA blocked before reading isMaster reply header";
-
-        // write out the full message now, even though another read() call will read the rest.
-        auto hdrBytes = reinterpret_cast<const uint8_t*>(replyMsg->header().view2ptr());
+    ConnectEvent{stream}.skip();
 
-        stream->pushRead({hdrBytes, hdrBytes + sizeof(MSGHEADER::Value)});
+    // simulate isMaster reply.
+    stream->simulateServer(
+        rpc::Protocol::kOpQuery,
+        [](RemoteCommandRequest request) -> RemoteCommandResponse {
+            ASSERT_EQ(std::string{request.cmdObj.firstElementFieldName()}, "isMaster");
+            ASSERT_EQ(request.dbname, "admin");
 
-        auto dataBytes = reinterpret_cast<const uint8_t*>(replyMsg->buf());
-        auto pastHeader = dataBytes;
-        std::advance(pastHeader, sizeof(MSGHEADER::Value));  // skip the header this time
-
-        stream->pushRead({pastHeader, dataBytes + static_cast<std::size_t>(replyMsg->size())});
-    }
-
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-        log() << "NIA blocked before reading isMaster reply data";
-    }
+            RemoteCommandResponse response;
+            response.data = BSON("minWireVersion" << mongo::minWireVersion << "maxWireVersion"
+                                                  << mongo::maxWireVersion);
+            return response;
+        });
 
+    auto expectedMetadata = BSON("meep"
+                                 << "beep");
     auto expectedCommandReply = BSON("boop"
                                      << "bop"
                                      << "ok" << 1.0);
-    auto expectedMetadata = BSON("meep"
-                                 << "beep");
 
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
+    // simulate user command
+    stream->simulateServer(rpc::Protocol::kOpCommandV1,
+                           [&](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               ASSERT_EQ(std::string{request.cmdObj.firstElementFieldName()},
+                                         "foo");
+                               ASSERT_EQ(request.dbname, "testDB");
 
-        log() << "blocked after write(), reading user command request";
+                               RemoteCommandResponse response;
+                               response.data = expectedCommandReply;
+                               response.metadata = expectedMetadata;
+                               return response;
+                           });
 
-        std::vector<uint8_t> messageData{stream->popWrite()};
+    auto res = fut.get();
 
-        Message msg(messageData.data(), false);
-        auto request = rpc::makeRequest(&msg);
+    ASSERT(callbackCalled);
+    ASSERT_EQ(res.data, expectedCommandReply);
+    ASSERT_EQ(res.metadata, expectedMetadata);
+}
 
-        // the command we requested should be running.
-        ASSERT_EQ(request->getCommandName(), "foo");
-        ASSERT_EQ(request->getDatabase(), "testDB");
+class NetworkInterfaceASIOConnectionHookTest : public NetworkInterfaceASIOTest {
+public:
+    void setUp() override {}
 
-        // we should be using op command given our previous isMaster reply.
-        ASSERT(request->getProtocol() == rpc::Protocol::kOpCommandV1);
+    void start(std::unique_ptr<NetworkConnectionHook> hook) {
+        auto factory = stdx::make_unique<AsyncMockStreamFactory>();
+        // keep unowned pointer, but pass ownership to NIA
+        _streamFactory = factory.get();
+        _net = stdx::make_unique<NetworkInterfaceASIO>(std::move(factory), std::move(hook));
+        _net->startup();
+    }
+};
 
-        rpc::CommandReplyBuilder replyBuilder;
-        replyBuilder.setMetadata(expectedMetadata).setCommandReply(expectedCommandReply);
-        auto replyMsg = replyBuilder.done();
+template <typename T>
+void assertThrowsStatus(stdx::future<T>&& fut, const Status& s) {
+    ASSERT([&] {
+        try {
+            std::forward<stdx::future<T>>(fut).get();
+            return false;
+        } catch (const DBException& ex) {
+            return ex.toStatus() == s;
+        }
+    }());
+}
 
-        replyMsg->header().setResponseTo(msg.header().getId());
+TEST_F(NetworkInterfaceASIOConnectionHookTest, ValidateHostInvalid) {
+    bool validateCalled = false;
+    bool hostCorrect = false;
+    bool isMasterReplyCorrect = false;
+    bool makeRequestCalled = false;
+    bool handleReplyCalled = false;
+
+    auto validationFailedStatus = Status(ErrorCodes::AlreadyInitialized, "blahhhhh");
+
+    start(makeTestHook(
+        [&](const HostAndPort& remoteHost, const RemoteCommandResponse& isMasterReply) {
+            validateCalled = true;
+            hostCorrect = (remoteHost == testHost);
+            isMasterReplyCorrect = (isMasterReply.data["TESTKEY"].str() == "TESTVALUE");
+            return validationFailedStatus;
+        },
+        [&](const HostAndPort& remoteHost) -> StatusWith<boost::optional<RemoteCommandRequest>> {
+            makeRequestCalled = true;
+            return {boost::none};
+        },
+        [&](const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
+            handleReplyCalled = true;
+            return Status::OK();
+        }));
+
+    stdx::promise<RemoteCommandResponse> done;
+    auto doneFuture = done.get_future();
+
+    net().startCommand({},
+                       {testHost,
+                        "blah",
+                        BSON("foo"
+                             << "bar")},
+                       [&](StatusWith<RemoteCommandResponse> result) {
+                           try {
+                               done.set_value(uassertStatusOK(result));
+                           } catch (...) {
+                               done.set_exception(std::current_exception());
+                           }
+                       });
 
-        // write out the full message now, even though another read() call will read the rest.
-        auto hdrBytes = reinterpret_cast<const uint8_t*>(replyMsg->header().view2ptr());
+    auto stream = streamFactory().blockUntilStreamExists(testHost);
 
-        stream->pushRead({hdrBytes, hdrBytes + sizeof(MSGHEADER::Value)});
+    ConnectEvent{stream}.skip();
+
+    // simulate isMaster reply.
+    stream->simulateServer(rpc::Protocol::kOpQuery,
+                           [](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               RemoteCommandResponse response;
+                               response.data = BSON("minWireVersion"
+                                                    << mongo::minWireVersion << "maxWireVersion"
+                                                    << mongo::maxWireVersion << "TESTKEY"
+                                                    << "TESTVALUE");
+                               return response;
+                           });
+
+    // we should stop here.
+    assertThrowsStatus(std::move(doneFuture), validationFailedStatus);
+    ASSERT(validateCalled);
+    ASSERT(hostCorrect);
+    ASSERT(isMasterReplyCorrect);
+
+    ASSERT(!makeRequestCalled);
+    ASSERT(!handleReplyCalled);
+}
 
-        auto dataBytes = reinterpret_cast<const uint8_t*>(replyMsg->buf());
-        auto pastHeader = dataBytes;
-        std::advance(pastHeader, sizeof(MSGHEADER::Value));  // skip the header this time
+TEST_F(NetworkInterfaceASIOConnectionHookTest, MakeRequestReturnsError) {
+    bool makeRequestCalled = false;
+    bool handleReplyCalled = false;
+
+    Status makeRequestError{ErrorCodes::DBPathInUse, "bloooh"};
+
+    start(makeTestHook(
+        [&](const HostAndPort& remoteHost, const RemoteCommandResponse& isMasterReply)
+            -> Status { return Status::OK(); },
+        [&](const HostAndPort& remoteHost) -> StatusWith<boost::optional<RemoteCommandRequest>> {
+            makeRequestCalled = true;
+            return makeRequestError;
+        },
+        [&](const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
+            handleReplyCalled = true;
+            return Status::OK();
+        }));
+
+    stdx::promise<RemoteCommandResponse> done;
+    auto doneFuture = done.get_future();
+
+    net().startCommand({},
+                       {testHost,
+                        "blah",
+                        BSON("foo"
+                             << "bar")},
+                       [&](StatusWith<RemoteCommandResponse> result) {
+                           try {
+                               done.set_value(uassertStatusOK(result));
+                           } catch (...) {
+                               done.set_exception(std::current_exception());
+                           }
+                       });
 
-        stream->pushRead({pastHeader, dataBytes + static_cast<std::size_t>(replyMsg->size())});
-    }
+    auto stream = streamFactory().blockUntilStreamExists(testHost);
+    ConnectEvent{stream}.skip();
+
+    // simulate isMaster reply.
+    stream->simulateServer(rpc::Protocol::kOpQuery,
+                           [](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               RemoteCommandResponse response;
+                               response.data = BSON("minWireVersion" << mongo::minWireVersion
+                                                                     << "maxWireVersion"
+                                                                     << mongo::maxWireVersion);
+                               return response;
+                           });
+
+    // We should stop here.
+    assertThrowsStatus(std::move(doneFuture), makeRequestError);
+
+    ASSERT(makeRequestCalled);
+    ASSERT(!handleReplyCalled);
+}
 
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-    }
+TEST_F(NetworkInterfaceASIOConnectionHookTest, MakeRequestReturnsNone) {
+    bool makeRequestCalled = false;
+    bool handleReplyCalled = false;
+
+    start(makeTestHook(
+        [&](const HostAndPort& remoteHost, const RemoteCommandResponse& isMasterReply)
+            -> Status { return Status::OK(); },
+        [&](const HostAndPort& remoteHost) -> StatusWith<boost::optional<RemoteCommandRequest>> {
+            makeRequestCalled = true;
+            return {boost::none};
+        },
+        [&](const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
+            handleReplyCalled = true;
+            return Status::OK();
+        }));
+
+    stdx::promise<RemoteCommandResponse> done;
+    auto doneFuture = done.get_future();
+
+    auto commandRequest = BSON("foo"
+                               << "bar");
+
+    net().startCommand({},
+                       {testHost, "blah", commandRequest},
+                       [&](StatusWith<RemoteCommandResponse> result) {
+                           try {
+                               done.set_value(uassertStatusOK(result));
+                           } catch (...) {
+                               done.set_exception(std::current_exception());
+                           }
+                       });
 
-    {
-        stream->waitUntilBlocked();
-        auto guard = MakeGuard([&] { stream->unblock(); });
-    }
 
-    auto res = fut.get();
+    auto stream = streamFactory().blockUntilStreamExists(testHost);
+    ConnectEvent{stream}.skip();
+
+    // simulate isMaster reply.
+    stream->simulateServer(rpc::Protocol::kOpQuery,
+                           [](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               RemoteCommandResponse response;
+                               response.data = BSON("minWireVersion" << mongo::minWireVersion
+                                                                     << "maxWireVersion"
+                                                                     << mongo::maxWireVersion);
+                               return response;
+                           });
+
+    auto commandReply = BSON("foo"
+                             << "boo"
+                             << "ok" << 1.0);
+
+    auto metadata = BSON("aaa"
+                         << "bbb");
+
+    // Simulate user command.
+    stream->simulateServer(rpc::Protocol::kOpCommandV1,
+                           [&](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               ASSERT_EQ(commandRequest, request.cmdObj);
+
+                               RemoteCommandResponse response;
+                               response.data = commandReply;
+                               response.metadata = metadata;
+                               return response;
+                           });
+
+    // We should get back the reply now.
+    auto reply = doneFuture.get();
+    ASSERT_EQ(reply.data, commandReply);
+    ASSERT_EQ(reply.metadata, metadata);
+}
 
-    ASSERT(callbackCalled);
-    ASSERT_EQ(res.data, expectedCommandReply);
-    ASSERT_EQ(res.metadata, expectedMetadata);
+TEST_F(NetworkInterfaceASIOConnectionHookTest, HandleReplyReturnsError) {
+    bool makeRequestCalled = false;
+
+    bool handleReplyCalled = false;
+    bool handleReplyArgumentCorrect = false;
+
+    BSONObj hookCommandRequest = BSON("1ddd"
+                                      << "fff");
+    BSONObj hookRequestMetadata = BSON("wdwd" << 1212);
+
+    BSONObj hookCommandReply = BSON("blah"
+                                    << "blah"
+                                    << "ok" << 1.0);
+    BSONObj hookReplyMetadata = BSON("1111" << 2222);
+
+    Status handleReplyError{ErrorCodes::AuthSchemaIncompatible, "daowdjkpowkdjpow"};
+
+    start(makeTestHook(
+        [&](const HostAndPort& remoteHost, const RemoteCommandResponse& isMasterReply)
+            -> Status { return Status::OK(); },
+        [&](const HostAndPort& remoteHost) -> StatusWith<boost::optional<RemoteCommandRequest>> {
+            makeRequestCalled = true;
+            return {boost::make_optional<RemoteCommandRequest>(
+                {testHost, "foo", hookCommandRequest, hookRequestMetadata})};
+
+        },
+        [&](const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
+            handleReplyCalled = true;
+            handleReplyArgumentCorrect =
+                (response.data == hookCommandReply) && (response.metadata == hookReplyMetadata);
+            return handleReplyError;
+        }));
+
+    stdx::promise<RemoteCommandResponse> done;
+    auto doneFuture = done.get_future();
+    auto commandRequest = BSON("foo"
+                               << "bar");
+    net().startCommand({},
+                       {testHost, "blah", commandRequest},
+                       [&](StatusWith<RemoteCommandResponse> result) {
+                           try {
+                               done.set_value(uassertStatusOK(result));
+                           } catch (...) {
+                               done.set_exception(std::current_exception());
+                           }
+                       });
+
+    auto stream = streamFactory().blockUntilStreamExists(testHost);
+    ConnectEvent{stream}.skip();
+
+    // simulate isMaster reply.
+    stream->simulateServer(rpc::Protocol::kOpQuery,
+                           [](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               RemoteCommandResponse response;
+                               response.data = BSON("minWireVersion" << mongo::minWireVersion
+                                                                     << "maxWireVersion"
+                                                                     << mongo::maxWireVersion);
+                               return response;
+                           });
+
+    // Simulate hook reply
+    stream->simulateServer(rpc::Protocol::kOpCommandV1,
+                           [&](RemoteCommandRequest request) -> RemoteCommandResponse {
+                               ASSERT_EQ(request.cmdObj, hookCommandRequest);
+                               ASSERT_EQ(request.metadata, hookRequestMetadata);
+
+                               RemoteCommandResponse response;
+                               response.data = hookCommandReply;
+                               response.metadata = hookReplyMetadata;
+                               return response;
+                           });
+
+    assertThrowsStatus(std::move(doneFuture), handleReplyError);
+
+    ASSERT(makeRequestCalled);
+    ASSERT(handleReplyCalled);
+    ASSERT(handleReplyArgumentCorrect);
 }
 
 TEST_F(NetworkInterfaceASIOTest, setAlarm) {
diff --git a/src/mongo/executor/network_interface_mock_test.cpp b/src/mongo/executor/network_interface_mock_test.cpp
index 011e0f0924e..283ec71fe59 100644
--- a/src/mongo/executor/network_interface_mock_test.cpp
+++ b/src/mongo/executor/network_interface_mock_test.cpp
@@ -33,9 +33,10 @@
 #include <utility>
 
 #include "mongo/base/status.h"
-#include "mongo/executor/network_interface.h"
 #include "mongo/executor/network_connection_hook.h"
+#include "mongo/executor/network_interface.h"
 #include "mongo/executor/network_interface_mock.h"
+#include "mongo/executor/test_network_connection_hook.h"
 #include "mongo/executor/thread_pool_mock.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/unittest.h"
@@ -44,44 +45,6 @@ namespace mongo {
 namespace executor {
 namespace {
 
-template <typename ValidateFunc, typename RequestFunc, typename ReplyFunc>
-class TestConnectionHook final : public NetworkConnectionHook {
-public:
-    TestConnectionHook(ValidateFunc&& validateFunc,
-                       RequestFunc&& requestFunc,
-                       ReplyFunc&& replyFunc)
-        : _validateFunc(std::forward<ValidateFunc>(validateFunc)),
-          _requestFunc(std::forward<RequestFunc>(requestFunc)),
-          _replyFunc(std::forward<ReplyFunc>(replyFunc)) {}
-
-    Status validateHost(const HostAndPort& remoteHost,
-                        const RemoteCommandResponse& isMasterReply) override {
-        return _validateFunc(remoteHost, isMasterReply);
-    }
-
-    StatusWith<boost::optional<RemoteCommandRequest>> makeRequest(const HostAndPort& remoteHost) {
-        return _requestFunc(remoteHost);
-    }
-
-    Status handleReply(const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
-        return _replyFunc(remoteHost, std::move(response));
-    }
-
-private:
-    ValidateFunc _validateFunc;
-    RequestFunc _requestFunc;
-    ReplyFunc _replyFunc;
-};
-
-template <typename Val, typename Req, typename Rep>
-static std::unique_ptr<TestConnectionHook<Val, Req, Rep>> makeTestHook(Val&& validateFunc,
-                                                                       Req&& requestFunc,
-                                                                       Rep&& replyFunc) {
-    return stdx::make_unique<TestConnectionHook<Val, Req, Rep>>(std::forward<Val>(validateFunc),
-                                                                std::forward<Req>(requestFunc),
-                                                                std::forward<Rep>(replyFunc));
-}
-
 class NetworkInterfaceMockTest : public mongo::unittest::Test {
 public:
     NetworkInterfaceMockTest() : _net{}, _executor(&_net, 1) {}
diff --git a/src/mongo/executor/remote_command_request.h b/src/mongo/executor/remote_command_request.h
index 325455ec1da..91a3689f61c 100644
--- a/src/mongo/executor/remote_command_request.h
+++ b/src/mongo/executor/remote_command_request.h
@@ -31,8 +31,9 @@
 #include <string>
 
 #include "mongo/db/jsobj.h"
-#include "mongo/util/net/hostandport.h"
 #include "mongo/rpc/metadata.h"
+#include "mongo/rpc/request_interface.h"
+#include "mongo/util/net/hostandport.h"
 #include "mongo/util/time_support.h"
 
 namespace mongo {
@@ -72,6 +73,15 @@ struct RemoteCommandRequest {
         : RemoteCommandRequest(
               theTarget, theDbName, theCmdObj, rpc::makeEmptyMetadata(), timeoutMillis) {}
 
+    RemoteCommandRequest(const HostAndPort& theTarget,
+                         const rpc::RequestInterface& request,
+                         const Milliseconds timeoutMillis = kNoTimeout)
+        : RemoteCommandRequest(theTarget,
+                               request.getDatabase().toString(),
+                               request.getCommandArgs(),
+                               request.getMetadata(),
+                               timeoutMillis) {}
+
     std::string toString() const;
 
     HostAndPort target;
diff --git a/src/mongo/executor/remote_command_response.cpp b/src/mongo/executor/remote_command_response.cpp
index a27d6856f24..a0b1baeeb79 100644
--- a/src/mongo/executor/remote_command_response.cpp
+++ b/src/mongo/executor/remote_command_response.cpp
@@ -30,11 +30,19 @@
 
 #include "mongo/executor/remote_command_response.h"
 
+#include "mongo/rpc/reply_interface.h"
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
 namespace executor {
 
+// TODO(amidvidy): we currently discard output docs when we use this constructor. We should
+// have RCR hold those too, but we need more machinery before that is possible.
+RemoteCommandResponse::RemoteCommandResponse(const rpc::ReplyInterface& rpcReply,
+                                             Milliseconds millis)
+    : RemoteCommandResponse(rpcReply.getCommandReply(), rpcReply.getMetadata(), std::move(millis)) {
+}
+
 std::string RemoteCommandResponse::toString() const {
     return str::stream() << "RemoteResponse -- "
                          << " cmd:" << data.toString();
diff --git a/src/mongo/executor/remote_command_response.h b/src/mongo/executor/remote_command_response.h
index 0f3e1c9ce0e..65d3f72c66b 100644
--- a/src/mongo/executor/remote_command_response.h
+++ b/src/mongo/executor/remote_command_response.h
@@ -34,6 +34,11 @@
 #include "mongo/util/time_support.h"
 
 namespace mongo {
+
+namespace rpc {
+class ReplyInterface;
+}  // namespace rpc
+
 namespace executor {
 
 
@@ -46,6 +51,8 @@ struct RemoteCommandResponse {
     RemoteCommandResponse(BSONObj dataObj, BSONObj metadataObj, Milliseconds millis)
         : data(std::move(dataObj)), metadata(std::move(metadataObj)), elapsedMillis(millis) {}
 
+    RemoteCommandResponse(const rpc::ReplyInterface& rpcReply, Milliseconds millis);
+
     std::string toString() const;
 
     BSONObj data;
diff --git a/src/mongo/executor/test_network_connection_hook.h b/src/mongo/executor/test_network_connection_hook.h
new file mode 100644
index 00000000000..0294b23cd38
--- /dev/null
+++ b/src/mongo/executor/test_network_connection_hook.h
@@ -0,0 +1,87 @@
+/**
+ *    Copyright (C) 2015 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.
+ */
+
+#include <boost/optional.hpp>
+#include <memory>
+
+#include "mongo/base/status_with.h"
+#include "mongo/executor/network_connection_hook.h"
+#include "mongo/stdx/memory.h"
+
+namespace mongo {
+namespace executor {
+
+
+/**
+ * A utility for creating one-off NetworkConnectionHook instances from inline lambdas. This is
+ * only to be used in testing code, not in production.
+ */
+template <typename ValidateFunc, typename RequestFunc, typename ReplyFunc>
+class TestConnectionHook final : public NetworkConnectionHook {
+public:
+    TestConnectionHook(ValidateFunc&& validateFunc,
+                       RequestFunc&& requestFunc,
+                       ReplyFunc&& replyFunc)
+        : _validateFunc(std::forward<ValidateFunc>(validateFunc)),
+          _requestFunc(std::forward<RequestFunc>(requestFunc)),
+          _replyFunc(std::forward<ReplyFunc>(replyFunc)) {}
+
+    Status validateHost(const HostAndPort& remoteHost,
+                        const RemoteCommandResponse& isMasterReply) override {
+        return _validateFunc(remoteHost, isMasterReply);
+    }
+
+    StatusWith<boost::optional<RemoteCommandRequest>> makeRequest(const HostAndPort& remoteHost) {
+        return _requestFunc(remoteHost);
+    }
+
+    Status handleReply(const HostAndPort& remoteHost, RemoteCommandResponse&& response) {
+        return _replyFunc(remoteHost, std::move(response));
+    }
+
+private:
+    ValidateFunc _validateFunc;
+    RequestFunc _requestFunc;
+    ReplyFunc _replyFunc;
+};
+
+/**
+ * Factory function for TestConnectionHook instances. Needed for template type deduction, so that
+ * one can instantiate a TestConnectionHook instance without uttering the unutterable (types).
+ */
+template <typename Val, typename Req, typename Rep>
+std::unique_ptr<TestConnectionHook<Val, Req, Rep>> makeTestHook(Val&& validateFunc,
+                                                                Req&& requestFunc,
+                                                                Rep&& replyFunc) {
+    return stdx::make_unique<TestConnectionHook<Val, Req, Rep>>(std::forward<Val>(validateFunc),
+                                                                std::forward<Req>(requestFunc),
+                                                                std::forward<Rep>(replyFunc));
+}
+
+}  // namespace executor
+}  // namespace mongo