net.server_epoll: Add debug logging for delayed reading In :onreadable, if there is still buffered incoming data after reading from the socket (as indicated by the :dirty method, usually because LuaSocket has an 8k buffer that's full but it read a smaller amount), another attempt to read is scheduled via this :pausefor method. This is also called from some other places where it would be pointless to read because there shouldn't be any data. In the delayed read case, this should report that the socket is "dirty". If it reports that the socket is "clean" then the question is where the buffer contents went? If this doesn't get logged after the scheduled time (0.000001s by default) then this would suggests a problem with timer or scheduling.

--- a/net/server_epoll.lua	Sat Dec 07 17:39:29 2019 +0100
+++ b/net/server_epoll.lua	Sat Dec 07 19:05:10 2019 +0100
@@ -660,6 +660,7 @@
 	self._pausefor = addtimer(t, function ()
 		self._pausefor = nil;
 		self:set(true);
+		self:debug("Resuming after pause, connection is %s", not self.conn and "missing" or self.conn:dirty() and "dirty" or "clean");
 		if self.conn and self.conn:dirty() then
 			self:onreadable();
 		end