Make Websocket send queue configurable

doc/rippled-example.cfg

@@ -273,6 +273,12 @@
 #               keep rippled from connecting to other instances of rippled or
 #               prevent RPC and WebSocket clients from connecting.
 #
+#   send_queue_limit = = [1..65535]
+#
+#       A Websocket will disconnect when its send queue exceeds this limit.
+#       The default is 100. A larger value may help with erratic disconnects but
+#       may adversely affect server performance.
+#
 # WebSocket permessage-deflate extension options
 #
 #   These settings configure the optional permessage-deflate extension

src/ripple/rpc/impl/ServerHandlerImp.cpp

@@ -832,6 +832,7 @@ to_Port(ParsedPort const& parsed, std::ostream& log)
     p.ssl_chain = parsed.ssl_chain;
     p.ssl_ciphers = parsed.ssl_ciphers;
     p.pmd_options = parsed.pmd_options;
+    p.ws_queue_limit = parsed.ws_queue_limit;
 
     return p;
 }

src/ripple/server/Port.h

@@ -58,6 +58,9 @@ struct Port
     // port in the range [0, 65535] where 0 means unlimited.
     int limit = 0;
 
+    // Websocket disconnects if send queue exceeds this limit
+    std::uint16_t ws_queue_limit;
+
     // Returns `true` if any websocket protocols are specified
     bool websockets() const;
 
@@ -87,6 +90,7 @@ struct ParsedPort
     std::string ssl_ciphers;
     beast::websocket::permessage_deflate pmd_options;
     int limit = 0;
+    std::uint16_t ws_queue_limit;
 
     boost::optional<boost::asio::ip::address> ip;
     boost::optional<std::uint16_t> port;

src/ripple/server/impl/BaseWSPeer.h

@@ -217,21 +217,18 @@ void
 BaseWSPeer<Handler, Impl>::
 send(std::shared_ptr<WSMsg> w)
 {
-    // Maximum send queue size
-    static std::size_t constexpr limit = 100;
     if(! strand_.running_in_this_thread())
         return strand_.post(std::bind(
             &BaseWSPeer::send, impl().shared_from_this(),
                 std::move(w)));
     if(do_close_)
         return;
-    if(wq_.size() >= limit)
+    if(wq_.size() > port().ws_queue_limit)
     {
         JLOG(this->j_.info()) <<
             "closing slow client";
         cr_.code = static_cast<beast::websocket::close_code::value>(4000);
         cr_.reason = "Client is too slow.";
-        static_assert(limit >= 1, "");
         wq_.erase(std::next(wq_.begin()), wq_.end());
         close();
         return;

src/ripple/server/impl/Port.cpp

@@ -205,6 +205,34 @@ parse_Port (ParsedPort& port, Section const& section, std::ostream& log)
         }
     }
 
+    {
+        auto const result = section.find("send_queue_limit");
+        if (result.second)
+        {
+            try
+            {
+                port.ws_queue_limit =
+                    beast::lexicalCastThrow<std::uint16_t>(result.first);
+
+                // Queue must be greater than 0
+                if (port.ws_queue_limit == 0)
+                    Throw<std::exception>();
+            }
+            catch (std::exception const&)
+            {
+                log <<
+                    "Invalid value '" << result.first << "' for key " <<
+                    "'send_queue_limit' in [" << section.name() << "]\n";
+                Rethrow();
+            }
+        }
+        else
+        {
+            // Default Websocket send queue size limit
+            port.ws_queue_limit = 100;
+        }
+    }
+
     populate (section, "admin", log, port.admin_ip, true, {});
     populate (section, "secure_gateway", log, port.secure_gateway_ip, false,
         port.admin_ip.get_value_or({}));