Config Update *without* service interuption?

[Steve Hotz]

Hi All,

I know gdnsd has been used for Wikimedia ...

Working with an organization that wants minimal downtime on config switchover/update (i.e. the few seconds on reload is being noticed) ... any tips/techniques that might help??

thanks,

sh

[Brandon Black]

gdnsd already has support for a nearly seamless overlapped restart.  All startup delays in the new daemon happen while the old is still answering queries, and then new sockets are created with SO_REUSEPORT before stopping the old sockets/daemon.  This is what happens by default when using "gdnsd restart".

The SO_REUSEPORT part requires Linux kernel 3.9+ (or BSD).  The other caveat is that the overlapped restart isn't systemd-compatible.  There's some work in progress on doing things in a vastly more complicated way that will work with systemd, but it's not ready for release yet.

--Brandon