# Resolv-replace problem **URL:** \ **Category:** Ruby\ **Created:** [January 22, 2007, 11:45pm UTC](https://www.ruby-forum.com/t/resolv-replace-problem/82999 "2007-01-22T23:45:06Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![mly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a9a28c/32.png) [@mly](https://www.ruby-forum.com/u/mly)\ **Post date:** [January 22, 2007, 11:45pm UTC](https://www.ruby-forum.com/t/resolv-replace-problem/82999/1 "2007-01-22T23:45:06Z")
After running through aproximately 512 ip to name resolutions, the resolv-replace library seems to become very slow and starts blocking threads. Any ideas? Any good alternatives for doing ip address to name lookups on thousands of systems? – Matt It’s not what I know that counts. It’s what I can remember in time to use. ---
**Author:** ![mly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a9a28c/32.png) [@mly](https://www.ruby-forum.com/u/mly)\ **Post date:** [January 22, 2007, 11:55pm UTC](https://www.ruby-forum.com/t/resolv-replace-problem/82999/2 "2007-01-22T23:55:08Z")
On Tue, 2007-01-23 at 07:44 +0900, Matt L. wrote: > Any good alternatives for doing ip address to name lookups on thousands of > systems? You could have a look at Ruby/Cares[[http://cares.rubyforge.org/](http://cares.rubyforge.org/)]. It’s a wrapper for c-ares, a library that performs name-resolving asynchronously. Feedback welcome 🙂 Best regards, Andre ---
**Author:** ![mly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a9a28c/32.png) [@mly](https://www.ruby-forum.com/u/mly)\ **Post date:** [January 23, 2007, 12:50am UTC](https://www.ruby-forum.com/t/resolv-replace-problem/82999/3 "2007-01-23T00:50:21Z")
On Jan 22, 2007, at 14:44, Matt L. wrote: > After running through aproximately 512 ip to name resolutions, the > resolv-replace library seems to become very slow and starts > blocking threads. Any ideas? > > Any good alternatives for doing ip address to name lookups on > thousands of systems? I’ve experienced this problem and assumed it was due to resolv- replace waiting for the destination name servers to time out, but didn’t verify. Have you examined this possibility? If you’ve got 1000 bogus host names, 100 threads and a 30 second timeout per thread you’ll still wait at least 5 minutes for all of them to fail to resolve. – Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net) I LIT YOUR GEM ON FIRE! ---
**Author:** ![mly](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a9a28c/32.png) [@mly](https://www.ruby-forum.com/u/mly)\ **Post date:** [January 23, 2007, 12:57am UTC](https://www.ruby-forum.com/t/resolv-replace-problem/82999/4 "2007-01-23T00:57:22Z")
On Tue, 23 Jan 2007, Eric H. wrote: > Have you examined this possibility? > > If you’ve got 1000 bogus host names, 100 threads and a 30 second timeout per > thread you’ll still wait at least 5 minutes for all of them to fail to > resolve. Shouldn’t have to wait for all of the lookups to fail. Every time EACH lookup fails, the threads should continue. I have a limit in my program of 50 threads. After about 512 lookups, the number of threads goes from 50 active to 6 or 7 active. Even when using the same address range over and over. – Matt It’s not what I know that counts. It’s what I can remember in time to use.