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


Hi Jean-Francois B. Gagne,

On Sun, Jan 8, 2017 at 8:39 PM, Jean-Francois B. Gagne
<jeanfrancois.gagne@xxxxxxxxxxx> wrote:
> 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...) ?
Yes this can be done.  Kristian what you think ?
> 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).
Created a mdev for this task MDEV-11744. I am not sure how to do this.
It will take some time.
> Many thanks