Re: [Tarantool-patches] [PATCH v15 11/11] box/journal: redesign journal operations

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Fri, Mar 20, 2020 at 01:58:42PM +0300, Konstantin Osipov wrote:
> * Cyrill Gorcunov <gorcunov@gmail.com> [20/03/20 13:34]:
> > > >  
> > > > -	if (txn_write_to_wal(req) != 0)
> > > > +	fiber_set_txn(fiber(), NULL);
> > > > +	if (journal_write(req) != 0) {
> > > > +		fiber_set_txn(fiber(), txn);
> > > 
> > > I wonder why do you need to clear/set txn in txn_commit()?
> 
> Forgive me for being really painful about it, but why not use
> different complete callbacks for sync and async wal writes?-)
> Under the hood they will still call txn_complete(), but one will
> assert, and another will not?

Hmm. If I remember correctly we've been planning to use callbacks
only for async writes. Actually I can introduce callback helper
for sync writes as well but this ruines the whole idea, no?

I can easily hide this bit test inside txn_complete itself and
for sync write there will be plain txn_complete call, like

txn_commit
	...
	journal_write();
	...
	txn_complete();

ie the whole idea was to not use callbacks for sync write, no?
...
> > > >  
> > > > -	/*
> > > > -	 * In case of non-yielding journal the transaction could already
> > > > -	 * be done and there is nothing to wait in such cases.
> > > > -	 */
> > > >  	if (!txn_has_flag(txn, TXN_IS_DONE)) {
> > > > -		bool cancellable = fiber_set_cancellable(false);
> > > > -		fiber_yield();
> > > > -		fiber_set_cancellable(cancellable);
> > > > +		txn->signature = req->res;
> > > > +		txn_complete(txn);
> > > > +		fiber_set_txn(fiber(), NULL);
> > > 
> 
> I mean fiber_set_txn() is done twice, if I am not mistaken.

True, this one is redundant. Thanks!