xaminmo: (Logo IBM CATE)
[personal profile] xaminmo
DNS query timeouts are mediated by the environment variables:

RES_TIMEOUT
RES_RETRY

The defaults are 5 and 4 respectively. Each retry doubles the timeout from before.

5 + 10 + 20 + 50 = 75 seconds.

Multiply this by the number of nameservers you have listed in /etc/resolv.conf and that's your DNS timeout PER QUERY when DNS is unreachable.



The minimum values are 1 and 1, which means:

1 + 2 = 3 seconds per nameserver.

If your network is routinely laggy, overloaded or has packet drops, then setting this to minimums could lead to unexpected and intermittant DNS failures.

However, something like this could let you use multiple nameservers and not have to worry about SSH hanging for 5 minutes in your DR site.



The best place to make these changes are /etc/environment. Log out and back in, then restart any processes you want to have faster timeouts.

For anything started and owned by init, you may need need to reboot.


-JD

Profile

eserver: (Default)
IBM POWER servers

June 2017

S M T W T F S
    123
45678 910
11121314151617
18192021222324
252627282930 

Syndicate

RSS Atom

Most Popular Tags

Style Credit

Expand Cut Tags

No cut tags
Page generated Jul. 21st, 2017 10:29 am
Powered by Dreamwidth Studios