"Jakub K" <slonymaillist at gmail.com> writes:
> Hello,
> i am new in slony and i have question, about how it's works.
> Q: slony is pull or push replication? or both?

When it combines "publish" and "subscribe," that implies a bit of
both, though it mostly looks like "pull," as that's where the bulk of
the work takes place.

> I set replication using slonik, than start slon daemon on subsrciber
> (sub) and publisher (pub).  And now, subsrciber is asking for data
> or publisher is sending data? How often?  -S SYNC check interval
> means how often are data asking (sub) or sending (pub)

"How often" is essentially controlled by the origin; it is there that
the "check interval" is used to determine if a SYNC event should be
published.

  -> If, within the sync_interval period, replication work has arrived,
     the origin will generate a SYNC event.

  -> If the origin is quiet (e.g. - not receiving any replicable work),
     there will still be a SYNC event each sync_interval_timeout
     milliseconds.

The SYNC event is published via the LISTEN/NOTIFY system in
PostgreSQL, which will cause a quiescent subscriber to wake up and
know it has new work to do.  That's when the "pulling" takes place.
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