Re: [tarantool-patches] [PATCH v3 11/14] txn: introduce asynchronous txn commit

["Георгий Кириченко" <georgy@tarantool.org>]

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On Thursday, June 13, 2019 5:34:00 PM MSK Vladimir Davydov wrote:
> On Sun, Jun 09, 2019 at 11:44:40PM +0300, Georgy Kirichenko wrote:
> > diff --git a/src/box/txn.c b/src/box/txn.c

> I don't see why we need to have in_txn() in on_commit/rollback triggers.
> Could you please point me?
Unfortunately lua on_commit triggers use it (because of vshard requirements) 
and I'm don't see the right way to remove it.
> 
> > diff --git a/src/box/wal.c b/src/box/wal.c
> > index e868a8e71..eff48b4fe 100644
> > --- a/src/box/wal.c
> > +++ b/src/box/wal.c
> > @@ -272,6 +272,8 @@ tx_schedule_f(va_list ap)
> > 
> >  			struct journal_entry *req =
> >  			
> >  				stailq_shift_entry(&writer->schedule_queue,
> >  				
> >  						   struct journal_entry, fifo);
> > 
> > +			if (req->on_done_cb != NULL)
> > +				req->on_done_cb(req, req->on_done_cb_data);
> > 
> >  			req->done = true;
> >  			fiber_cond_broadcast(&req->done_cond);
> 
> Why do we need cond if we have a callback? Can't we wake up the awaiting
> fiber from the callback?
The condition and the done variable is required the time when all transaction 
data could be purged. Definitely it could not be done while on_done_cb because 
we will lost transaction status in this case. I think there are some ways to 
handle this but I think the solution would be too complicated.
I use the callback to process txn finalization and call on_commit/on_rollback 
trigger one of them signals an applier fiber to collect transaction and 
determine replication state.


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