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authorMatthew Wild <mwild1@gmail.com>2020-06-25 15:29:49 +0100
committerMatthew Wild <mwild1@gmail.com>2020-06-25 15:29:49 +0100
commitd080fee3235102dd6a20cdfcd53f1ee080a1266b (patch)
tree8df55f859b30222d668ee096689a736cf417e153
parent3ff48b8386fdc9faf6e7f9d99a93858ec3a49728 (diff)
downloadprosody-d080fee3235102dd6a20cdfcd53f1ee080a1266b.tar.gz
prosody-d080fee3235102dd6a20cdfcd53f1ee080a1266b.zip
net.dns: Add jitter to spread queries and reduce failures due to congestion
-rw-r--r--net/dns.lua22
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