Hi. I'm trying to set up a Storm cluster using Kerberos authentication. I can
make that work in a static case: that is, I can generate keytabs and jaas.conf
files and the right stuff in storm.yaml and zoo.cfg and the like and it's all
working.
Now, for my next trick: being able to change the keytabs on a routine basis,
without having to take the whole cluster down.
There are two things in particular about which I'm unclear.
First, and most importantly, the examples I've found for setting this up all
use a single Kerberos principal (storm@REALM) to authenticate to Zookeeper.
And of course something sets the ACL on /storm and the stuff below it to be
storm@REALM.
So if we update the credentials for storm@REALM, we presumably need to update
those credentials on every Storm host in fairly short order, or individual
supervisors (or Nimbus or the UI) won't be able to authenticate to Zookeeper.
But coordinating that at more-or-less the same time seems tricky, especially in
an environment where some central host can't just reach out and coordinate all
the changes at once.
I don't know if it's possible to set storm.zookeeper.superACL to a list of
credentials, one per host, so that everything can still make changes under
/storm but all the individual hosts can update their credentials on their own
schedule.
Second, I'm not quite sure what happens to roll the keytabs themselves. If I
update a keytab, do I have to restart the supervisor (or whatever) that's using
that keytab? Or do the various components just try to authenticate
periodically, and if they fail, re-read the keytab file -- or do they never
cache the contents of the keytab file, and always read it fresh, so if we just
update the keytab file with the latest key shortly after we change the
credential on the KDC?
If someone could share some details on how they handle key rolls on a
production cluster, that'd be hugely useful. I'd be happy to try to update the
"running an authenticated Storm cluster" docs to reflect how that sort of
detail works.
And please accept my apologies in advance if I'm saying something dumb here: I
am far from being an expert on Kerberos.
Thanks!
-Steve
