maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Andrei,

On Mar 01, Andrei Elkin wrote:
> > On Feb 28, Andrei wrote:
> >> revision-id: 880e92a48ba (mariadb-10.6.6-16-g880e92a48ba)
> >> parent(s): 4030a9fb2eb
> >> author: Andrei
> >> committer: Andrei
> >> timestamp: 2022-02-21 14:58:13 +0200
> >> message:
> >> 
> >> MDEV-27760 event may non stop replicate in circular semisync setup
> >> 
> >> diff --git a/sql/slave.cc b/sql/slave.cc
> >> index c0eef02ca7a..a1f4f4f0081 100644
> >> --- a/sql/slave.cc
> >> +++ b/sql/slave.cc
> >> @@ -6186,13 +6186,13 @@ static int queue_event(Master_info* mi, const uchar *buf, ulong event_len)
> >>    bool is_rows_event= false;
> >>    /*
> >>      The flag has replicate_same_server_id semantics and is raised to accept
> >> -    a same-server-id event on the semisync slave, for both the gtid and legacy
> >> -    connection modes.
> >> -    Such events can appear as result of this server recovery so the event
> >> -    was created there and replicated elsewhere right before the crash. At recovery
> >> -    it could be evicted from the server's binlog.
> >> -  */
> >> -  bool do_accept_own_server_id= false;
> >> +    a same-server-id event group by the gtid strict mode semisync slave.
> >> +    Own server-id events can appear as result of this server crash-recovery:
> >> +    the transaction was created on this server then being master, got replicated
> >> +    elsewhere right before the crash before commit;
> >> +    finally at recovery the transaction gets evicted from the server's binlog.
> >> + */
> >> +  static bool do_accept_own_server_id= false;
> >
> > No, sorry, it cannot be static. If you need to preserve it between
> > events, you can keep it, for example, in Master_info.
> 
> The var is set by Gtid events to serve as a marker of the whole current Gtid-headed
> group of event.
> Only next Gtid event may change the current value.
> 
> Why can't it?

Why it cannot be static? Because it's not a property of the server, it's
a property of a specific replication stream. Technically one can have a
multi-source and do_accept_own_server_id could have different values for
different masters.

> > So, the question now is, why do you need to preserve the value of
> > do_accept_own_server_id between queue_event invocations?
> 
> The flag as said above applies to the whole group of events, so it's
> preserved at least through so many 
> queue_event() calls as many event in the group (I count Gtid itself in).

As far as I can see, you can calculate it for every event just the same.

> >> @@ -6281,6 +6281,8 @@ static int queue_event(Master_info* mi, const uchar *buf, ulong event_len)
> >>                      dbug_rows_event_count = 0;
> >>                    };);
> >>  #endif
> >> +  s_id= uint4korr(buf + SERVER_ID_OFFSET);
> >> +
> >>    mysql_mutex_lock(&mi->data_lock);
> >>  
> >>    switch (buf[EVENT_TYPE_OFFSET]) {
> >> @@ -6722,6 +6724,11 @@ static int queue_event(Master_info* mi, const uchar *buf, ulong event_len)
> >>  
> >>      ++mi->events_queued_since_last_gtid;
> >>      inc_pos= event_len;
> >> +
> >> +    do_accept_own_server_id=
> >> +      (s_id == global_system_variables.server_id && rpl_semi_sync_slave_enabled
> >> +       && mi->using_gtid != Master_info::USE_GTID_NO && opt_gtid_strict_mode) ?
> >> +      true : false;

Regards,
Sergei
VP of MariaDB Server Engineering
and security@xxxxxxxxxxx