Software / code / prosody
Diff
net/dns.lua @ 10957:8902cecbdd39
net.dns: Add jitter to spread queries and reduce failures due to congestion
| author | Matthew Wild <mwild1@gmail.com> |
|---|---|
| date | Thu, 25 Jun 2020 15:29:49 +0100 |
| parent | 10956:03a09fa02e8e |
| child | 10958:25680ece29c2 |
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--- a/net/dns.lua Thu Jun 25 15:28:23 2020 +0100 +++ b/net/dns.lua Thu Jun 25 15:29:49 2020 +0100 @@ -72,6 +72,8 @@ local get, set = ztact.get, ztact.set; local default_timeout = 15; +local default_jitter = 1; +local default_retry_jitter = 2; -------------------------------------------------- module dns local _ENV = nil; @@ -668,6 +670,8 @@ resolver.delays = { 1, 3 }; +resolver.jitter = have_timer and default_jitter or nil; +resolver.retry_jitter = have_timer and default_retry_jitter or nil; function resolver:addnameserver(address) -- - - - - - - - - - addnameserver self.server = self.server or {}; @@ -855,7 +859,7 @@ packet = header..question, server = self.best_server, delay = 1, - retry = socket.gettime() + self.delays[1] + retry = socket.gettime() + self.delays[1]; qclass = qclass; qtype = qtype; qname = qname; @@ -869,7 +873,13 @@ if not conn then return nil, err; end - conn:send (o.packet) + if self.jitter then + timer.add_task(math.random()*self.jitter, function () + conn:send(o.packet); + end); + else + conn:send(o.packet); + end -- remember which coroutine wants the answer if co then @@ -920,8 +930,16 @@ sock, err = self:getsocket(o.server); if sock then retried = true; + if self.retry_jitter then + local delay = self.delays[((o.retries-1)%#self.delays)+1] + (math.random()*self.retry_jitter); + log("debug", "retry %d in %0.2fs", o.retries, delay); + timer.add_task(delay, function () + sock:send(o.packet); + end); + else log("debug", "retry %d (immediate)", o.retries); sock:send(o.packet); + end end end if not retried then
