Get zmq socket events in IO read callback. Allow batch recvs.

examples/ev_subscriber.lua

@@ -19,6 +19,11 @@
 -- THE SOFTWARE.
 
 local zmq = require"zmq"
+local z_NOBLOCK = zmq.NOBLOCK
+local z_EVENTS = zmq.EVENTS
+local z_POLLIN = zmq.POLLIN
+local z_POLLOUT = zmq.POLLOUT
+local z_POLLIN_OUT = z_POLLIN + z_POLLOUT
 local ev = require'ev'
 local loop = ev.Loop.default
 
@@ -51,27 +56,43 @@ local function sub_worker(loop, ctx, msg_cb)
 	-- need idle watcher since ZeroMQ sockets are edge-triggered instead of level-triggered
 	local s_io_idle
 	local s_io_read
-	s_io_idle = ev.Idle.new(function()
-		local msg, err = s:recv(zmq.NOBLOCK)
+	local max_recvs = 10
+	local function s_recv(recv_cnt)
+		local msg, err = s:recv(z_NOBLOCK)
 		if err == 'timeout' then
+			-- need to block on read IO
+			return false
+		end
+		self:msg_cb(msg)
+		if recv_cnt > 1 then
+			return s_recv(recv_cnt - 1)
+		end
+		return true
+	end
+	s_io_idle = ev.Idle.new(function()
+		if not s_recv(max_recvs) then
 			-- need to block on read IO
 			s_io_idle:stop(loop)
 			s_io_read:start(loop)
-			return
 		end
-		self:msg_cb(msg)
 	end)
 	s_io_idle:start(loop)
 	s_io_read = ev.IO.new(function()
-		s_io_idle:start(loop)
-		s_io_read:stop(loop)
+		local events = s:getopt(z_EVENTS)
+		if events == z_POLLIN or events == z_POLLIN_OUT then
+			if s_recv(max_recvs) then
+				-- read IO is not block, enable idle watcher to handle reads.
+				s_io_idle:start(loop)
+				s_io_read:stop(loop)
+			end
+		end
 	end, s:getopt(zmq.FD), ev.READ)
 	self.s_io_idle = s_io_idle
 	self.s_io_read = s_io_read
 	return self
 end
 
-local ctx = zmq.init(1)
+local ctx = zmq.init()
 
 -- message handling function.
 local function handle_msg(worker, msg)