Re: BUG #16643: PG13 - Logical replication - initial startup never finishes and gets stuck in startup loop

On 2020-Nov-05, Amit Kapila wrote:

> On Wed, Nov 4, 2020 at 7:19 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > On 2020-Nov-04, Amit Kapila wrote:
> >
> > > On Thu, Oct 15, 2020 at 8:20 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > > > * STREAM COMMIT bug?
> > > >   In apply_handle_stream_commit, we do CommitTransactionCommand, but
> > > >   apparently in a tablesync worker we shouldn't do it.
> > >
> > > In the tablesync stage, we don't allow streaming. See pgoutput_startup
> > > where we disable streaming for the init phase. As far as I understand,
> > > for tablesync we create the initial slot during which streaming will
> > > be disabled then we will copy the table (here logical decoding won't
> > > be used) and then allow the apply worker to get any other data which
> > > is inserted in the meantime. Now, I might be missing something here
> > > but if you can explain it a bit more or share some test to show how we
> > > can reach here via tablesync worker then we can discuss the possible
> > > solution.
> >
> > Hmm, okay, that sounds like there would be no bug then.  Maybe what we
> > need is just an assert in apply_handle_stream_commit that
> > !am_tablesync_worker(), as in the attached patch.  Passes tests.
> >
> 
> +1. But do we want to have this Assert only in stream_commit API or
> all stream APIs as well?

Well, the only reason I care about this is that apply_handle_commit
contains a comment that we must not do CommitTransactionCommand in the
syncworker case; so if you look at apply_handle_stream_commit and note
that it doesn't concern it about that, you become concerned that it
might be broken.  I don't think the other routines handling the "stream"
thing have that issue.