net.server: Add a predrain callaback just before writes
Allows sneaking in things in the write buffer just before it's sent to
the network stack. For example ack requests, compression flushes or
other things that make sense to send after stanzas or other things.
This ensures any additional trailing data sent is included in the same
write, and possibly the same TCP packet. Other methods used such as
timers or nextTick might not have the same effect as it depends on
scheduling.
--- a/net/server_epoll.lua Mon Aug 16 11:37:51 2021 +0200
+++ b/net/server_epoll.lua Mon Aug 16 12:34:52 2021 +0200
@@ -472,6 +472,7 @@
function interface:onwritable()
self:onconnect();
if not self.conn then return; end -- could have been closed in onconnect
+ self:on("predrain");
local buffer = self.writebuffer;
local data = buffer or "";
if type(buffer) == "table" then
--- a/net/server_event.lua Mon Aug 16 11:37:51 2021 +0200
+++ b/net/server_event.lua Mon Aug 16 12:34:52 2021 +0200
@@ -449,6 +449,7 @@
self.onstatus = listener.onstatus;
self.ondetach = listener.ondetach;
self.onattach = listener.onattach;
+ self.onpredrain = listener.onpredrain;
self.ondrain = listener.ondrain;
self:onattach(data);
end
@@ -464,6 +465,8 @@
end
function interface_mt:onreadtimeout()
end
+function interface_mt:onpredrain()
+end
function interface_mt:ondrain()
end
function interface_mt:ondetach()
@@ -490,6 +493,7 @@
onincoming = listener.onincoming; -- will be called when client sends data
ontimeout = listener.ontimeout; -- called when fatal socket timeout occurs
onreadtimeout = listener.onreadtimeout; -- called when socket inactivity timeout occurs
+ onpredrain = listener.onpredrain; -- called before writes
ondrain = listener.ondrain; -- called when writebuffer is empty
ondetach = listener.ondetach; -- called when disassociating this listener from this connection
onstatus = listener.onstatus; -- called for status changes (e.g. of SSL/TLS)
@@ -540,6 +544,7 @@
interface.eventwritetimeout = false
end
end
+ interface:onpredrain();
interface.writebuffer = { t_concat(interface.writebuffer) }
local succ, err, byte = interface.conn:send( interface.writebuffer[1], 1, interface.writebufferlen )
--vdebug( "write data:", interface.writebuffer, "error:", err, "part:", byte )
--- a/net/server_select.lua Mon Aug 16 11:37:51 2021 +0200
+++ b/net/server_select.lua Mon Aug 16 12:34:52 2021 +0200
@@ -294,6 +294,7 @@
local dispatch = listeners.onincoming
local status = listeners.onstatus
local disconnect = listeners.ondisconnect
+ local predrain = listeners.onpredrain
local drain = listeners.ondrain
local onreadtimeout = listeners.onreadtimeout;
local detach = listeners.ondetach
@@ -338,6 +339,7 @@
dispatch = listeners.onincoming
disconnect = listeners.ondisconnect
status = listeners.onstatus
+ predrain = listeners.onpredrain
drain = listeners.ondrain
handler.onreadtimeout = listeners.onreadtimeout
detach = listeners.ondetach
@@ -552,6 +554,9 @@
listeners.onconnect(handler);
end
end
+ if predrain then
+ predrain(handler);
+ end
buffer = table_concat( bufferqueue, "", 1, bufferqueuelen )
succ, err, byte = send( socket, buffer, 1, bufferlen )
count = ( succ or byte or 0 ) * STAT_UNIT