[bind10-dev] Refreshing a slave server on startup, was document zonemgr configurations

Shane Kerr shane at isc.org
Wed Dec 14 11:50:47 UTC 2011


All,

On Wed, 2011-12-14 at 10:08 +0800, Jerry.zzchen wrote:
> On Fri, Dec 9, 2011 at 3:09 AM, Jeremy C. Reed <jreed at isc.org> wrote:
> > Please help provide some succinct explanations for the the zonemgr
> > configurations. Any clarifications would be appreciated.
> >       reload_jitter
> >       This value is a real number. The default is 0.75.
> >
> > * What is this reload_jitter? Why is the default 0.75? I attempted to
> > read the code several times. Why is it called "reload"?  Why doesn't it
> > have a maximum? Can it be disabled?
> The initial goal of reload_jitter is to avoid many zones need to do
> refresh at the same time on zonemgr startup.
> For more information, please refer to http://bind10.isc.org/ticket/387.

FYI, we had an internal discussion within ISC recently about startups
and massive zone checking.

An alternative way to reducing load may be to keep track of last refresh
information in secondary storage somewhere (an SQLite database would be
fine for this). Then when you re-start you only need to check zones that
are not fresh. Actually, you probably want to check them all (in case
you missed a NOTIFY), but you can at least prioritize the ones you know
need to be checked.

We may also consider using a TCP session if we have a lot of SOA RR to
check from a single master, and probably send the queries without
waiting for a response on that channel for efficiency.

Thinking further, it would be even better if there was something like
IXFR but for an entire server. So, something like a TCP session like
this:

        Client: Here is logical timestamp of the last update I got from
        you.
        
        Server: Okay, I know which zones you are slaving, and here is a
        list of all of the zones which have changed

One could add an EDNS with this logical timestamp on every SOA answer so
clients could keep track of this.

--
Shane




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