We should call res_init() on Linux systems after failure in getaddrinfo().
Handle cases when the DNS resolver has been changed by resetting the cache.
Should ideally be fixed in glibc but do not think they will as outlined http://sourceware.org/bugzilla/show_bug.cgi?id=3675
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This is a minor issue effecting DNS on RedHat derivative linux distributions due to an implementation choice in GLIBC in those distributions. The issue is, if you make changes to the DNS resolver underneath MongoDB you will need to restart your database under any RHEL based Linux.
This does not effect Debian derivatives as they use a patched version of GLIBC.