On Mon, Mar 24, 2014 at 5:54 PM, Magnus Hagander <magnus@hagander.net> wrote: > I was looking at http://www.postgresql.org/docs/devel/static/bgworker.html > with a client today. > > It says: > "Unlike RegisterBackgroundWorker, which can only be called from within the > postmaster,RegisterDynamicBackgroundWorker must be called from a regular > backend." > > Is that the correct restriction? In particular, don't we allow calling > RegisterDynamicBackgroundWorker from another background worker? (In the > launcher/worker kind of scenario, like AutoVacuum).
Yes, you can start a dynamic background worker from another background worker, have a look for example at contrib/worker_spi. Perhaps the correct wording would be "RegisterDynamicBackgroundWorker must be called from a regular backend or another background worker".
That's what I thought. Can a dynamic background worker start *another* dynamic background worker, or can they only be started from "first level" background workers?
> Also: > "Background workers are expected to be continuously running; if they exit > cleanly, postgres will restart them immediately. " > > This doesn't apply to dynamic ones, which we might want to clarify. Do we > have a "term" for non-dynamic background workers? "static workers"?
In the code or the documentation, there is no explicit differentiation, bgworkers are either called plainly "bgworker", or "dynamic bgworker". Perhaps the solution here is simply to say "background workers started by the postmaster are expected blabla".
