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| author | Matthew Wild <mwild1@gmail.com> | 2020-06-25 15:29:49 +0100 |
|---|---|---|
| committer | Matthew Wild <mwild1@gmail.com> | 2020-06-25 15:29:49 +0100 |
| commit | d080fee3235102dd6a20cdfcd53f1ee080a1266b (patch) | |
| tree | 8df55f859b30222d668ee096689a736cf417e153 | |
| parent | 3ff48b8386fdc9faf6e7f9d99a93858ec3a49728 (diff) | |
| download | prosody-d080fee3235102dd6a20cdfcd53f1ee080a1266b.tar.gz prosody-d080fee3235102dd6a20cdfcd53f1ee080a1266b.zip | |
net.dns: Add jitter to spread queries and reduce failures due to congestion
| -rw-r--r-- | net/dns.lua | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/net/dns.lua b/net/dns.lua index 1dcb0479..6f5f28d4 100644 --- a/net/dns.lua +++ b/net/dns.lua @@ -72,6 +72,8 @@ local ztact = { -- public domain 20080404 lua@ztact.com 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 @@ end 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 @@ function resolver:query(qname, qtype, qclass) -- - - - - - - - - - -- query 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 @@ function resolver:query(qname, qtype, qclass) -- - - - - - - - - - -- query 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 @@ function resolver:servfail(sock, err) 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 |