DNS resolution fails after resolv.conf update

[Bernd Eckenfels]

Hello,

not sure how I feel about the res_init(). Depending on the backends
used this might be expensive. Especially since it wont be rate
limited. The negative-ttl of 10s is for single records I thing. So at a
minimum you should rate-limit res_init to the same negative-ttl time).

But another aspect: this is also a problem for positive answers. Only
because you get an answer does not mean it is the NS you wanted to
query. Maybe a background refreshing could solve both? Would also
reduce concurrency.

debian/ubuntu BTW seems to have a rather elaborate reload hook
mechanism:
http://manpages.ubuntu.com/manpages/gutsy/man8/resolvconf.8.html


But that is I guess hard to integrate with JVM.

Gruss
Bernd


Am Mon, 04 May 2015 17:38:46 +0200
schrieb Stanislav Baiduzhyi <sbaiduzh at redhat.com>:

> Hi All,
> 
> We are facing an issue with DNS server caching on RHEL-based distros:
> after the update of resolv.conf java application cannot resolve the
> hosts any more.
> 
> Reproducer is very simple:
> 1. Clean /etc/resolv.conf or connect to vpn and use vpn-only
> nameserver. 2. Launch the minimal java app [1].
> 3. Restore the /etc/resolv.conf or disconnect from vpn
> (/etc/resolv.conf should be updated with accessible nameserver at
> this moment). 4. Notice that name resolution continues to fail.
> 
> I've prepared a small webrev that fixes the issue [2], but would like
> to hear some ideas/criticism first. If the patch looks ok to
> everyone, please create an issue for this, and I will submit it for
> approval/sponsorship.
> 
> [1]: 
> https://e61b615da46327c9050d624b0a3783ba21c6b125.googledrive.com/host/0B5Kp-cB1sXJrfnZ4NHZ0S1V3UTJZcDFra3RwUFZjQXY5WVZzUkwtTTd0Z1IyR1JmbDZPSVk/resolvconf-reinit/ResolvingHost.java
> 
> [2]:
> https://e61b615da46327c9050d624b0a3783ba21c6b125.googledrive.com/host/0B5Kp-cB1sXJrfnZ4NHZ0S1V3UTJZcDFra3RwUFZjQXY5WVZzUkwtTTd0Z1IyR1JmbDZPSVk/resolvconf-reinit/
>