| Subject: | Semantics of "retry" and "retrans" options has changed with 1.03 |
1) A meaning of a "retry" option in Net::DNS::Resolver::new has changed
between versions 1.02 and 1.03, while its documentations remains unchanged:
retry
print 'number of tries: ', $resolver->retry, "\n";
$resolver->retry(2);
Get or set the number of times to try the query. The default is 4.
Actually the "retry" in 1.02 and earlier meant the number of
attempts (=tries, i.e. 4 transmissions, at its default value of 4),
while with 1.03 the number of transmissions is one more, i.e. the
semantics became: 1 first transmission + "retry" repeats, total of 5.
The change is undocumented, and is unfortunate, as what could previously
be achieved by retry=>1, retrans=>5 -> one send and a 5 second timeout,
now became two sends with a total of 15 second timeout (5+10) on
an unresponsive DNS server.
2) a meaning of "retrans" has changed too: in 1.02 and earlier
one could achieve a single send and a one second timeout
(waiting for a reply) by setting retry=>1, retrans=>0.
Now with 1.03 the same setting causes rapid firing of retry+1
UDP packets and zero wait time, so in practice no answer is
received unless the information is already in a cache of a
fast and close DNS resolver.
The documentation states:
retrans
Get or set the retransmission interval The default is 5 seconds.
which does not mention doubling the interval with each attempt,
and does not say that the last (again doubled) interval is the
final timeout.