Occasionally we hit a bug where the ‘whois’ command hangs on one of our CentOS servers and goes CPU-bound. This has been happening on several CentOS versions, including 6.8. Specifically, this is a problem in jwhois, the whois client included in CentOS.
Apparently, CentOS (and RHEL, on whose source code it’s based) is missing a number of fixes that have been added to other Linux versions including Fedora over the last couple of years. So the problem is actually known and a fix has been available for years, it’s just not included in the product.
On Jan 26, 2010, Fedora received a fix (“Use select to wait for input (patch by Joshua Roys <joshua.roys AT gtri.gatech.edu>)”) for a new 4.0-19 build that resolved bug #469412 for precisely this issue. There are many more changes in Fedora’s jwhois after that, unlike its RHEL and CentOS equivalent, which in all the years since then received only a single update. This is also called 4.0-19, but it was made on Jun 23, 2011 and it includes only two fixes for unrelated issues that were fixed in Fedora’s jwhois updates 4.0-24 (Dec 20, 2010) and 4.0-26 (Mar 15, 2011), but not the earlier select fix or fixes for any of the other issues. CentOS is missing the “jwhois-4.0-select.patch” and that’s why WHOIS hangs.