User should be able to choose RabbitMQ network partition policy

[Gaëtan Trellu]

By defaut [1], the RabbitMQ network policy should not be set to autoheal
which could result to a split-brain but to pause_minority or even ignore.

With pause_minority, you get consistency while sacrificing availability.
The minority node(s) will pause and disconnect all clients. The clients
will reconnect to other nodes in the majority-half of the cluster and
resume normal operation.

With autoheal, you get availability while sacrificing consistency. The
cluster becomes "split-brained". The success of each RPC request is
contingent upon all participating connections involved in the request
being on the same partition as one another, which is not very likely.
So until the partition ends, the system will be in a degraded state and
most things are going to fail.

Source: [2]

User should be able to choose the policy by using an option in globals.yml

- [1] https://github.com/openstack/kolla-ansible/blob/stable/stein/ansible/roles/rabbitmq/templates/rabbitmq.conf.j2#L5
- [2] https://bugzilla.redhat.com/show_bug.cgi?id=1189480#c34

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/672562

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/stein
Review: https://review.opendev.org/686032

[OpenStack Infra (hudson-openstack)]

Change abandoned by Radosław Piliszek (<email address hidden>) on branch: stable/stein
Review: https://review.opendev.org/686032

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/672562
Committed: https://git.openstack.org/cgit/openstack/kolla-ansible/commit/?id=5b0a281d5122d1806f2e689f5b5c7f48658b41d7
Submitter: Zuul
Branch: master

commit 5b0a281d5122d1806f2e689f5b5c7f48658b41d7
Author: Gaëtan Trellu <email address hidden>
Date: Wed Jul 24 12:38:40 2019 -0400

    Set RabbitMQ cluster_partition_handling to pause_minority

    This is to avoid split-brain.

    This change also adds relevant docs that sort out the
    HA/quorum questions.

    Change-Id: I9a8c2ec4dbbd0318beb488548b2cde8f4e487dc1
    Closes-Bug: #1837761
    Co-authored-by: Radosław Piliszek <email address hidden>

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/kolla-ansible 9.0.0.0rc1 release candidate.