maria-developers team mailing list archive

[Nirbhay Choubey <nirbhay@xxxxxxxxxxx>]

Hi Serg,

On Mon, Jun 27, 2016 at 7:38 AM, Sergei Golubchik <serg@xxxxxxxxxxx> wrote:

> Hi, Nirbhay!
>
> On Jun 08, Nirbhay Choubey wrote:
> > revision-id: 075233312cc5bc6c242f4629f8293d4c67937f02
> (mariadb-10.1.14-10-g0752333)
> > parent(s): c9f05974e618a869563f2360ef1ca910974a4f1c
> > author: Nirbhay Choubey
> > committer: Nirbhay Choubey
> > timestamp: 2016-06-08 16:03:01 -0400
> > message:
> >
> > MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file
> >
> > Since wsrep_sync_wait & wsrep_causal_reads variables are related,
> > they are always kept in sync whenever one of them changes.
> > Same is tried on server start, where wsrep_sync_wait get updated
> > based on wsrep_causal_reads' value. But, since wsrep_causal_reads
> > is OFF by default, wsrep_sync_wait's value gets modified and loses
> > its WSREP_SYNC_WAIT_BEFORE_READ bit.
> >
> > Fixed by giving higher precedence to one that's explicitly set to
> > a non-default value and later to wsrep_sync_wait in case both are
> > set.
> >
> > diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
> > index d0798ef..fffb0cc 100644
> > --- a/sql/wsrep_mysqld.cc
> > +++ b/sql/wsrep_mysqld.cc
> > @@ -567,7 +567,39 @@ int wsrep_init()
> >
> >    wsrep_sst_auth_init(wsrep_sst_auth);
> >
> > -  wsrep_causal_reads_update(&global_system_variables);
> > +  /*
> > +    On server start, there is no way to detect whether the default value
> > +    for a system variable was set explicitly by the user.
> > +    Now, since wsrep_causal_reads & wsrep_sync_wait are used for same
> > +    purpose, a rule of precedence must be defined to keep their values
> > +    in sync. It goes as following:
>
> This is wrong. First, in 10.1 there is a way to detect whether the value
> was set by a user. I_S.SYSTEM_VARIABLES can show that.
>

sys_var::value_origin == CONFIG.  I wasn't aware of that.


> But even if you'd detected that, it won't help you do distinguish
> between
>
>   mysqld --wsrep-sync-wait=1 --wsrep-causal-reads=0
>   mysqld --wsrep-sync-wait=0 --wsrep-causal-reads=1
>
> The only correct solution is to handle this in the mysqld_get_one_option
> switch, updating the dependent option when one of these two is set.
>

Correct. I have committed another one using this approach.

http://lists.askmonty.org/pipermail/commits/2016-June/009503.html

Thank you.

- Nirbhay



>
> Regards,
> Sergei
> Chief Architect MariaDB
> and security@xxxxxxxxxxx
>