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Re: [External] Mdev-10664 Add statuses about optimistic parallel replication stalls.


Hi Sachin,

I am very happy to see you work on that.  Comments below.

On 8 January 2017 at 09:34, Sachin Setiya <sachin.setiya@xxxxxxxxxxx> wrote:

> I am stuck at one problem in Mdev-10664. Suppose there is multisource
> replication('master1' and 'master2' )
> and we want to  update status var, How to know which master_info to
> update ?. Does slave threads have current
> replication channel name? (I was not able to find any , I have looked
> in rpl_group_info)

By updating master_info above you mean updating the master_info RAM
structre, right ?  Not the master_info file...

The easier way to give visibility on parallel replication stalls is to add
a global status variable like slave_retried_transactions
(slave_optimistic_stalls ?).  However, this hides which multi-source
channel generated that stall (or retried transaction).  Is there a way to
show this information in SHOW SLAVE STATUS or in Performance Schema (Oracle
MySQL is exposing per-channel counter in P_S I thing...) ?

While you are working on this, might I suggest that you also expose
something like what BINLOG_COMMIT and BINLOG_GROUP_COMMIT the slave is
seeing from the master in conservative mode (and per-channel).  Today, to
monitor parallel replication, we need to get this information from the
master and maps it to the position including lag) of the slave.  It would
be great to be able to monitor a slave only by looking at the slave
(something like slave_binlog_commit_master and
slave_binlog_group_commit_master global status would be a 1st start).

Many thanks


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