/get_random_outs is now fully async using stackful coroutines (#142)

CMakeLists.txt

@@ -161,7 +161,7 @@ if(STATIC)
   set(Boost_USE_STATIC_LIBS ON)
   set(Boost_USE_STATIC_RUNTIME ON)
 endif()
-find_package(Boost 1.70 QUIET REQUIRED COMPONENTS chrono filesystem program_options regex serialization system thread)
+find_package(Boost 1.70 QUIET REQUIRED COMPONENTS chrono coroutine filesystem program_options regex serialization system thread)
 
 if (NOT (Boost_THREAD_LIBRARY STREQUAL monero_Boost_THREAD_LIBRARY_RELEASE))
   message(STATUS "Found Boost_THREAD_LIBRARY: ${Boost_THREAD_LIBRARY}")

src/CMakeLists.txt

@@ -56,6 +56,7 @@ target_link_libraries(monero-lws-daemon-common
     monero-lws-wire-json
     monero-lws-util
     ${Boost_CHRONO_LIBRARY}
+    ${Boost_COROUTINE_LIBRARY}
     ${Boost_PROGRAM_OPTIONS_LIBRARY}
     ${Boost_SYSTEM_LIBRARY}
     ${Boost_THREAD_LIBRARY}

src/net/zmq_async.h

@@ -143,20 +143,20 @@ namespace net { namespace zmq
 
   //! Cannot have an `async_read` and `async_write` at same time (edge trigger)
   template<typename F>
-  void async_read(async_client& sock, std::string& buffer, F&& f)
+  auto async_read(async_client& sock, std::string& buffer, F&& f)
   {
     // async_compose is required for correct strand invocation, etc
-    boost::asio::async_compose<F, void(boost::system::error_code, std::size_t)>(
+    return boost::asio::async_compose<F, void(boost::system::error_code, std::size_t)>(
       read_msg_op{sock, buffer}, f, *sock.asock
     );
   }
 
   //! Cannot have an `async_write` and `async_read` at same time (edge trigger)
   template<typename F>
-  void async_write(async_client& sock, epee::byte_slice msg, F&& f)
+  auto async_write(async_client& sock, epee::byte_slice msg, F&& f)
   {
     // async_compose is required for correct strand invocation, etc
-    boost::asio::async_compose<F, void(boost::system::error_code, std::size_t)>(
+    return boost::asio::async_compose<F, void(boost::system::error_code, std::size_t)>(
       write_msg_op{sock, std::move(msg)}, f, *sock.asock
     );
   }

src/rest_server.cpp

@@ -29,6 +29,7 @@
 #include <algorithm>
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/asio/io_service.hpp>
+#include <boost/asio/spawn.hpp>
 #include <boost/asio/steady_timer.hpp>
 #include <boost/asio/strand.hpp>
 #include <boost/beast/core/error.hpp>
@@ -116,66 +117,6 @@ namespace lws
     };
     using async_complete = void(expect<copyable_slice>);
 
-    expect<rpc::client*> thread_client(const rpc::client& gclient, const bool reset = false)
-    {
-      struct tclient
-      {
-        rpc::client client;
-        std::chrono::steady_clock::time_point last_connect;
-
-        explicit tclient() noexcept
-          : client(), last_connect(std::chrono::seconds{0})
-        {}
-      };
-      static boost::thread_specific_ptr<tclient> global;
-
-      tclient* thread_ptr = global.get();
-      if (!thread_ptr)
-      {
-        thread_ptr = new tclient;
-        global.reset(thread_ptr);
-      }
-
-      if (reset || !thread_ptr->client)
-      {
-        // This reduces ZMQ internal errors with lack of file descriptors
-        const auto now = std::chrono::steady_clock::now();
-        if (now - thread_ptr->last_connect < zmq_reconnect_backoff)
-          return {error::daemon_timeout};
-
-        // careful, gclient and thread_ptr->client could be aliased
-        expect<rpc::client> new_client = gclient.clone();
-        thread_ptr->client = rpc::client{};
-        thread_ptr->last_connect = now;
-        if (!new_client)
-          return new_client.error();
-
-        thread_ptr->client = std::move(*new_client);
-      }
-
-      return {std::addressof(thread_ptr->client)};
-    }
-
-    expect<void> send_with_retry(rpc::client& tclient, epee::byte_slice message, const std::chrono::seconds timeout)
-    {
-      expect<void> resp{common_error::kInvalidArgument};
-      for (unsigned i = 0; i < 2; ++i)
-      {
-        resp = tclient.send(message.clone(), timeout);
-        if (resp || resp != net::zmq::make_error_code(EFSM))
-          break;
-        // fix state machine by reading+discarding previously timed out response
-        auto read = tclient.get_message(timeout);
-        if (!read)
-        {
-          // message could've been delivered, then dropped in process failure
-          thread_client(tclient, true);
-          return read.error();
-        }
-      }
-      return resp;
-    }
-
     bool is_locked(std::uint64_t unlock_time, db::block_id last) noexcept
     {
       if (unlock_time > CRYPTONOTE_MAX_BLOCK_NUMBER)
@@ -316,7 +257,7 @@ namespace lws
       using response = epee::byte_slice; // sometimes async
       using async_response = rpc::daemon_status_response;
 
-      static expect<response> handle(const request&, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete> resume)
+      static expect<response> handle(const request&, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete>&& resume)
       {
         using info_rpc = cryptonote::rpc::GetInfo;
 
@@ -507,7 +448,7 @@ namespace lws
       using request = rpc::account_credentials;
       using response = rpc::get_address_info_response;
 
-      static expect<response> handle(const request& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>)
+      static expect<response> handle(const request& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>&&)
       {
         auto user = open_account(req, data.disk.clone());
         if (!user)
@@ -581,7 +522,7 @@ namespace lws
       using request = rpc::account_credentials;
       using response = rpc::get_address_txs_response;
 
-      static expect<response> handle(const request& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>)
+      static expect<response> handle(const request& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>&&)
       {
         auto user = open_account(req, data.disk.clone());
         if (!user)
@@ -705,138 +646,335 @@ namespace lws
       using response = void; // always asynchronous response
       using async_response = rpc::get_random_outs_response;
 
-      static expect<response> handle(request req, boost::asio::io_service& io, const rest_server_data& data, std::function<async_complete> resume)
+      static expect<response> handle(request&& req, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete>&& resume)
       {
         using distribution_rpc = cryptonote::rpc::GetOutputDistribution;
         using histogram_rpc = cryptonote::rpc::GetOutputHistogram;
         using distribution_rpc = cryptonote::rpc::GetOutputDistribution;
 
-        std::vector<std::uint64_t> amounts = std::move(req.amounts.values);
-
-        if (50 < req.count || 20 < amounts.size())
+        if (50 < req.count || 20 < req.amounts.values.size())
           return {lws::error::exceeded_rest_request_limit};
 
-        const expect<rpc::client*> tclient = thread_client(data.client);
-        if (!tclient)
-          return tclient.error();
-        if (*tclient == nullptr)
-          throw std::logic_error{"Unexpected rpc::client nullptr"};
+        std::sort(req.amounts.values.begin(), req.amounts.values.end(), std::greater<>{});
 
-        const std::greater<std::uint64_t> rsort{};
-        std::sort(amounts.begin(), amounts.end(), rsort);
-        const std::size_t ringct_count =
-          amounts.end() - std::lower_bound(amounts.begin(), amounts.end(), 0, rsort);
-
-        std::vector<lws::histogram> histograms{};
-        if (ringct_count < amounts.size())
+        struct frame
         {
-          // reuse allocated vector memory
-          amounts.resize(amounts.size() - ringct_count);
+          rest_server_data* parent;
+          net::zmq::async_client client;
+          boost::asio::steady_timer timer;
+          boost::asio::strand<boost::asio::io_context::executor_type> strand;
+          std::deque<std::pair<request, std::function<async_complete>>> resumers;
 
-          histogram_rpc::Request histogram_req{};
-          histogram_req.amounts = std::move(amounts);
-          histogram_req.min_count = 0;
-          histogram_req.max_count = 0;
-          histogram_req.unlocked = true;
-          histogram_req.recent_cutoff = 0;
+          frame(rest_server_data& parent, boost::asio::io_service& io, net::zmq::async_client client)
+            : parent(std::addressof(parent)),
+              client(std::move(client)),
+              timer(io),
+              strand(io.get_executor()),
+              resumers()
+          {}
+        };
 
-          epee::byte_slice msg = rpc::client::make_message("get_output_histogram", histogram_req);
-          MONERO_CHECK(send_with_retry(**tclient, std::move(msg), std::chrono::seconds{10}));
+        struct cached_result
+        {
+          std::weak_ptr<frame> status;
+          boost::mutex sync;
 
-          auto histogram_resp = (*tclient)->receive<histogram_rpc::Response>(std::chrono::minutes{3}, MLWS_CURRENT_LOCATION);
-          if (!histogram_resp)
-            return histogram_resp.error();
-          if (histogram_resp->histogram.size() != histogram_req.amounts.size())
-            return {lws::error::bad_daemon_response};
+          cached_result() noexcept
+            : status(), sync()
+          {}
+        };
 
-          histograms = std::move(histogram_resp->histogram);
+        static cached_result cache;
+        boost::unique_lock<boost::mutex> lock{cache.sync};
 
-          amounts = std::move(histogram_req.amounts);
-          amounts.insert(amounts.end(), ringct_count, 0);
+        auto active = cache.status.lock();
+        if (active)
+        {
+          active->resumers.emplace_back(std::move(req), std::move(resume));
+          return success();
         }
 
-        std::vector<std::uint64_t> distributions{};
-        if (ringct_count)
+        struct async_handler
         {
-          distribution_rpc::Request distribution_req{};
-          if (ringct_count == amounts.size())
-            distribution_req.amounts = std::move(amounts);
+          std::shared_ptr<frame> self_;
 
-          distribution_req.amounts.resize(1);
-          distribution_req.from_height = 0;
-          distribution_req.to_height = 0;
-          distribution_req.cumulative = true;
-
-          epee::byte_slice msg =
-            rpc::client::make_message("get_output_distribution", distribution_req);
-          MONERO_CHECK(send_with_retry(**tclient, std::move(msg), std::chrono::seconds{10}));
-
-          auto distribution_resp =
-            (*tclient)->receive<distribution_rpc::Response>(std::chrono::minutes{3}, MLWS_CURRENT_LOCATION);
-          if (!distribution_resp)
-            return distribution_resp.error();
-
-          if (distribution_resp->distributions.size() != 1)
-            return {lws::error::bad_daemon_response};
-          if (distribution_resp->distributions[0].amount != 0)
-            return {lws::error::bad_daemon_response};
-
-          distributions = std::move(distribution_resp->distributions[0].data.distribution);
-
-          if (amounts.empty())
-          {
-            amounts = std::move(distribution_req.amounts);
-            amounts.insert(amounts.end(), ringct_count - 1, 0);
-          }
-        }
-
-        class zmq_fetch_keys
-        {
-          /* `std::function` needs a copyable functor. The functor was made
-             const and copied in the function instead of using a reference to
-             make the callback in `std::function` thread-safe. This shouldn't
-             be a problem now, but this is just-in-case of a future refactor. */
-          rpc::client* tclient;
-        public:
-          zmq_fetch_keys(rpc::client* src) noexcept
-            : tclient(src)
+          explicit async_handler(std::shared_ptr<frame> self)
+            : self_(std::move(self))
           {}
 
-          zmq_fetch_keys(zmq_fetch_keys&&) = default;
-          zmq_fetch_keys(const zmq_fetch_keys&) = default;
-
-          expect<std::vector<output_keys>> operator()(std::vector<lws::output_ref> ids) const
+          void send_response(const boost::system::error_code error, expect<copyable_slice> value) const
           {
-            using get_keys_rpc = cryptonote::rpc::GetOutputKeys;
-            if (tclient == nullptr)
-              throw std::logic_error{"Unexpected nullptr in zmq_fetch_keys"};
+            assert(self_ != nullptr);
 
-            get_keys_rpc::Request keys_req{};
-            keys_req.outputs = std::move(ids);
+            std::deque<std::pair<request, std::function<async_complete>>> resumers;
+            {
+              const boost::lock_guard<boost::mutex> lock{cache.sync};
+              if (error)
+              {
+                // Prevent further resumers, ZMQ REQ/REP in bad state
+                MERROR("Failure in /get_random_outs: " << error.message());
+                if (value)
+                  value = {lws::error::daemon_timeout};
+                cache.status.reset();
+                resumers.swap(self_->resumers);
+              }
+              else
+              {
+                MDEBUG("Completed ZMQ request in /get_random_outs");
+                resumers.push_back(std::move(self_->resumers.front()));
+                self_->resumers.pop_front();
+              }
+            }
 
-            epee::byte_slice msg = rpc::client::make_message("get_output_keys", keys_req);
-            MONERO_CHECK(send_with_retry(*tclient, std::move(msg), std::chrono::seconds{10}));
+            for (const auto& r : resumers)
+              r.second(value);
+          }
 
-            auto keys_resp = tclient->receive<get_keys_rpc::Response>(std::chrono::seconds{10}, MLWS_CURRENT_LOCATION);
-            if (!keys_resp)
-              return keys_resp.error();
+          bool set_timeout(std::chrono::steady_clock::duration timeout, const bool expecting) const
+          {
+            assert(self_ != nullptr);
+            if (!self_->timer.expires_after(timeout) && expecting)
+              return false;
 
-            return {std::move(keys_resp->keys)};
+            auto& self = self_;
+            self->timer.async_wait(
+              [self] (boost::system::error_code error)
+              {
+                if (error == boost::asio::error::operation_aborted)
+                  return;
+
+                self->strand.dispatch(
+                  [self] ()
+                  {
+                    boost::system::error_code error{};
+                    MWARNING("Timeout on /get_random_outs ZMQ call");
+                    self->client.close = true;
+                    self->client.asock->cancel(error);
+                  },
+                  boost::asio::get_associated_allocator(*self)
+                );
+              }
+            );
+            return true;
+          }
+
+          void operator()(boost::asio::yield_context yield) const
+          {
+            if (!self_)
+              return;
+
+            std::chrono::steady_clock::time_point last{std::chrono::seconds{0}};
+            std::vector<std::uint64_t> distributions{};
+            request next{};
+
+            for (;;)
+            {
+              {
+                const boost::lock_guard<boost::mutex> lock{cache.sync};
+                if (self_->resumers.empty())
+                {
+                  cache.status.reset();
+                  self_->parent->store_async_client(std::move(self_->client));
+                  MDEBUG("Finishing ZMQ coroutine in /get_random_outs");
+                  return;
+                }
+                next = std::move(self_->resumers.front().first);
+              }
+
+              boost::system::error_code error{};
+              std::vector<lws::histogram> histograms{};
+              const std::size_t ringct_count =
+                next.amounts.values.end() -
+                  std::lower_bound(
+                    next.amounts.values.begin(), next.amounts.values.end(), 0, std::greater<>{}
+                  );
+
+              if (ringct_count < next.amounts.values.size())
+              {
+                // reuse allocated vector memory
+                next.amounts.values.resize(next.amounts.values.size() - ringct_count);
+
+                histogram_rpc::Request histogram_req{};
+                histogram_req.amounts = std::move(next.amounts.values);
+                histogram_req.min_count = 0;
+                histogram_req.max_count = 0;
+                histogram_req.unlocked = true;
+                histogram_req.recent_cutoff = 0;
+
+                epee::byte_slice msg = rpc::client::make_message("get_output_histogram", histogram_req);
+
+                MDEBUG("Fetching histograms for /get_random_outs");
+                set_timeout(std::chrono::seconds{10}, false);
+                net::zmq::async_write(self_->client, std::move(msg), yield[error]);
+                if (error)
+                  return send_response(error, async_ready());
+                if (!set_timeout(std::chrono::minutes{3}, true))
+                  return send_response(boost::asio::error::operation_aborted, async_ready());
+
+                std::string in;
+                net::zmq::async_read(self_->client, in, yield[error]);
+                if (error)
+                  return send_response(error, async_ready());
+                if (!self_->timer.cancel(error))
+                  return send_response(boost::asio::error::operation_aborted, async_ready());
+
+                histogram_rpc::Response histogram_resp{};
+                const expect<void> status =
+                  rpc::parse_response(histogram_resp, std::move(in));
+                if (!status)
+                  return send_response(boost::asio::error::invalid_argument, status.error());
+                if (histogram_resp.histogram.size() != histogram_req.amounts.size())
+                  return send_response(boost::asio::error::invalid_argument, {lws::error::bad_daemon_response});
+
+                histograms = std::move(histogram_resp.histogram);
+
+                next.amounts.values = std::move(histogram_req.amounts);
+                next.amounts.values.insert(next.amounts.values.end(), ringct_count, 0);
+              }
+
+              if (ringct_count && (distributions.empty() || (daemon_cache_timeout < std::chrono::steady_clock::now() - last)))
+              {
+                distribution_rpc::Request distribution_req{};
+                if (ringct_count == next.amounts.values.size())
+                {
+                  distribution_req.amounts = std::move(next.amounts.values);
+                  next.amounts.values.clear();
+                }
+
+                distribution_req.amounts.resize(1);
+                distribution_req.from_height = 0;
+                distribution_req.to_height = 0;
+                distribution_req.cumulative = true;
+
+                epee::byte_slice msg =
+                  rpc::client::make_message("get_output_distribution", distribution_req);
+
+                MDEBUG("Fetching distributions for /get_random_outs");
+                set_timeout(std::chrono::seconds{10}, false);
+                net::zmq::async_write(self_->client, std::move(msg), yield[error]);
+                if (error)
+                  return send_response(error, async_ready());
+                if (!set_timeout(std::chrono::minutes{3}, true))
+                  return send_response(boost::asio::error::operation_aborted, async_ready());
+
+                std::string in;
+                net::zmq::async_read(self_->client, in, yield[error]);
+                if (error)
+                  return send_response(error, async_ready());
+                if (!self_->timer.cancel(error))
+                  return send_response(boost::asio::error::operation_aborted, async_ready());
+
+                distribution_rpc::Response distribution_resp{};
+                const expect<void> status =
+                  rpc::parse_response(distribution_resp, std::move(in));
+                if (!status)
+                  return send_response(boost::asio::error::invalid_argument, status.error());
+                if (distribution_resp.distributions.size() != 1)
+                  return send_response(boost::asio::error::invalid_argument, {lws::error::bad_daemon_response});
+                if (distribution_resp.distributions[0].amount != 0)
+                  return send_response(boost::asio::error::invalid_argument, {lws::error::bad_daemon_response});
+
+                last = std::chrono::steady_clock::now();
+                distributions = std::move(distribution_resp.distributions[0].data.distribution);
+
+                if (next.amounts.values.empty())
+                {
+                  next.amounts.values = std::move(distribution_req.amounts);
+                  next.amounts.values.insert(
+                    next.amounts.values.end(), ringct_count - 1, 0
+                  );
+                }
+              }
+
+              class zmq_fetch_keys
+              {
+                /* `std::function` needs a copyable functor. The functor was made
+                   const and copied in the function instead of using a reference to
+                   make the callback in `std::function` thread-safe. This shouldn't
+                   be a problem now, but this is just-in-case of a future refactor. */
+                async_handler self_;
+                boost::asio::yield_context yield_;
+
+              public:
+                zmq_fetch_keys(async_handler self, boost::asio::yield_context yield)
+                  : self_(std::move(self)), yield_(std::move(yield))
+                {}
+
+                zmq_fetch_keys(zmq_fetch_keys&&) = default;
+                zmq_fetch_keys(const zmq_fetch_keys&) = default;
+
+                expect<std::vector<output_keys>> operator()(std::vector<lws::output_ref> ids) const
+                {
+                  using get_keys_rpc = cryptonote::rpc::GetOutputKeys;
+                  if (self_.self_ == nullptr)
+                    throw std::logic_error{"Unexpected nullptr in zmq_fetch_keys"};
+
+                  boost::system::error_code error{};
+                  get_keys_rpc::Request keys_req{};
+                  keys_req.outputs = std::move(ids);
+
+                  epee::byte_slice msg = rpc::client::make_message("get_output_keys", keys_req);
+
+                  self_.set_timeout(std::chrono::seconds{10}, false);
+                  net::zmq::async_write(self_.self_->client, std::move(msg), yield_[error]);
+
+                  if (error)
+                  {
+                    MERROR("Internal ZMQ error in /get_random_outs: " << error.message());
+                    return {error::daemon_timeout};
+                  }
+                  if (!self_.set_timeout(std::chrono::seconds{10}, true))
+                    return {error::daemon_timeout};
+
+                  std::string in;
+                  net::zmq::async_read(self_.self_->client, in, yield_[error]);
+                  if (error)
+                  {
+                    MERROR("Internal ZMQ error in /get_random_outs: " << error.message());
+                    return {error::daemon_timeout};
+                  }
+                  if (!self_.self_->timer.cancel(error))
+                    return {error::daemon_timeout};
+
+                  get_keys_rpc::Response keys_resp{};
+                  const expect<void> status =
+                    rpc::parse_response(keys_resp, std::move(in));
+                  if (!status)
+                    return status.error();
+
+                  return {std::move(keys_resp.keys)};
+                }
+              };
+
+              lws::gamma_picker pick_rct{std::move(distributions)};
+              auto rings = pick_random_outputs(
+                next.count,
+                epee::to_span(next.amounts.values),
+                pick_rct,
+                epee::to_mut_span(histograms),
+                zmq_fetch_keys{*this, yield}
+              );
+              distributions = pick_rct.take_offsets();
+              if (!rings)
+                return send_response(boost::asio::error::invalid_argument, rings.error());
+              else
+                send_response({}, json_response(async_response{std::move(*rings)}));
+            }
           }
         };
 
-        lws::gamma_picker pick_rct{std::move(distributions)};
-        auto rings = pick_random_outputs(
-          req.count,
-          epee::to_span(amounts),
-          pick_rct,
-          epee::to_mut_span(histograms),
-          zmq_fetch_keys{*tclient}
-        );
-        if (!rings)
-          return rings.error();
+        expect<net::zmq::async_client> client = data.get_async_client(io);
+        if (!client)
+          return client.error();
 
-        resume(json_response(async_response{std::move(*rings)}));
+        active = std::make_shared<frame>(data, io, std::move(*client));
+        cache.status = active;
+
+        active->resumers.emplace_back(std::move(req), std::move(resume));
+        lock.unlock();
+
+        MDEBUG("Starting new ZMQ coroutine in /get_random_outs");
+        boost::asio::spawn(active->strand, async_handler{active});
         return success();
       }
     };
@@ -846,7 +984,7 @@ namespace lws
       using request = rpc::account_credentials;
       using response = rpc::get_subaddrs_response;
 
-      static expect<response> handle(request const& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>)
+      static expect<response> handle(request const& req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>&&)
       {
         auto user = open_account(req, data.disk.clone());
         if (!user)
@@ -925,7 +1063,7 @@ namespace lws
         );
       }
 
-      static expect<response> handle(request req, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete> resume)
+      static expect<response> handle(request req, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete>&& resume)
       {
         struct frame
         {
@@ -1109,7 +1247,7 @@ namespace lws
       using request = rpc::account_credentials;
       using response = rpc::import_response;
 
-      static expect<response> handle(request req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>)
+      static expect<response> handle(request req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>&&)
       {
         bool new_request = false;
         bool fulfilled = false;
@@ -1149,7 +1287,7 @@ namespace lws
       using request = rpc::login_request;
       using response = rpc::login_response;
 
-      static expect<response> handle(request req, boost::asio::io_service& io, const rest_server_data& data, std::function<async_complete> resume)
+      static expect<response> handle(request req, boost::asio::io_service& io, const rest_server_data& data, std::function<async_complete>&& resume)
       {
         if (!key_check(req.creds))
           return {lws::error::bad_view_key};
@@ -1206,7 +1344,7 @@ namespace lws
       using request = rpc::provision_subaddrs_request;
       using response = rpc::new_subaddrs_response;
 
-      static expect<response> handle(request req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>)
+      static expect<response> handle(request req, const boost::asio::io_service&, const rest_server_data& data, std::function<async_complete>&&)
       {
         if (!req.maj_i && !req.min_i && !req.n_min && !req.n_maj)
           return {lws::error::invalid_range};
@@ -1494,7 +1632,7 @@ namespace lws
     };
 
     template<typename E>
-    expect<epee::byte_slice> call(std::string&& root, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete> resume)
+    expect<epee::byte_slice> call(std::string&& root, boost::asio::io_service& io, rest_server_data& data, std::function<async_complete>&& resume)
     {
       using request = typename E::request;
       using response = typename E::response;
@@ -1534,7 +1672,7 @@ namespace lws
     }
 
     template<typename E>
-    expect<epee::byte_slice> call_admin(std::string&& root, boost::asio::io_service&, rest_server_data& data, std::function<async_complete>)
+    expect<epee::byte_slice> call_admin(std::string&& root, boost::asio::io_service&, rest_server_data& data, std::function<async_complete>&&)
     {
       using request = typename E::request;
       
@@ -1575,7 +1713,7 @@ namespace lws
     struct endpoint
     {
       char const* const name;
-      expect<epee::byte_slice> (*const run)(std::string&&, boost::asio::io_service&, rest_server_data&, std::function<async_complete>);
+      expect<epee::byte_slice> (*const run)(std::string&&, boost::asio::io_service&, rest_server_data&, std::function<async_complete>&&);
       const unsigned max_size;
       const bool is_async;
     };