[wishlist] addition config items for wsrep_slave_threads and gcs.fc_limit

[Xav Paice]

On a busy cluster, we would like to be able to tune the replication to avoid flow control from slowing down the primary. So far, we've added the following manually to a second config file but adding things manually falls down when we add units.

wsrep_provider_options="gcs.fc_limit=10000"
wsrep_slave_threads=48

[Xav Paice (xavpaice)]

https://review.openstack.org/#/c/612876

[Xav Paice (xavpaice)]

Subscribed field-medium, the change in progress needs review

[Ryan Beisner (1chb1n)]

Thank you for your work on this. I want to make sure we have the necessary coverage and that we've discussed the product defaults in light of the proposed changes (ie. evaluate the charm's default stance, and potentially improve the db story by default).

Please see reviews @ https://review.openstack.org/#/c/612876/2.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/612876
Committed: https://git.openstack.org/cgit/openstack/charm-percona-cluster/commit/?id=7b7188b610c0ff19c6164fcecda0d6fdaf37f199
Submitter: Zuul
Branch: master

commit 7b7188b610c0ff19c6164fcecda0d6fdaf37f199
Author: Xav Paice <email address hidden>
Date: Wed Oct 24 16:04:32 2018 +1300

    Add wsrep-slave-threads and gcs-fc-limit

    These options allow tuning the Galera replication to avoid flow control from
    slowing down the primary.

    Change-Id: Ib275cae0db02e4c8c0a85fcc8cb138b26eb26982
    Closes-Bug: 1799622