The number of required plugins has increased to the extent that
controller on Zuul FT infrastructure almost runs out of memory [1].
This potentially induces various problems such as FT failure noises
or POST_FAILURE at the ansible task 'export-devstack-journal'.
To request expanded images such as ubuntu-focal-expanded (16GB) or
ubuntu-focal-32GB would be an option, but it turns out that would
lead us to another problematic situation. [2]
This patch, instead, addresses the issue by subdividing the memory
load. As a first step, introduce a new subnode 'tacker-controller',
on which both tacker-server and tacker-conductor are located.
Note:
* when we re-locate some other components to this new subnode, it might
better to rename it.
* `devstack_local_conf: {}` in .zuul.yaml is to cancel out the global
job.vars devstack_local_conf.post-config.$NEUTRON_DHCP_CONF, which
is not present on 'tacker-controller' in the first place.
* TACKER_MODE is set to 'standalone'. 'all-in-one' supposes core
services like nova, neutron, keystone, etc. api servers are located
on the same host as tacker-server.
* in devstack/lib/tacker:create_tacker_accounts, SERVICE_HOST should
have been TACKER_HOST. this minor fix is included.
* in roles/setup-default-vim/tasks/main.yaml, the same where conditions
were scattered but all tasks in it just needed to run on 'controller'
only. so let us wrap them all in a block.
* renamed devstack/plugin.sh:tacker_register_default_vim for clarity.
* policy file modification for Heat is now done by an ansible task.
it frees us from the co-location requirements for Tacker and Heat.
* drop devstack/lib/tacker:is_tacker_enabled as it's no longer needed.
[1]: we investigated how severe the memory load on 'controller' was
on Zuul FT infrastructure:
* The highest memory-consuming processes in desc order:
808.70MB (9.87%) 828112 /usr/sbin/mysqld
179.81MB (2.19%) 184124 ... /usr/local/bin/tacker-server ...
152.57MB (1.86%) 156232 ... /usr/local/bin/tacker-conductor .
146.67MB (1.79%) 150188 ... /usr/local/bin/neutron-server ...
132.96MB (1.62%) 136148 ... /usr/local/bin/neutron-server ...
129.08MB (1.58%) 132180 ... /usr/local/bin/heat-engine ...
127.48MB (1.56%) 130544 ... /usr/local/bin/heat-engine ...
122.16MB (1.49%) 125092 nova-apiuWSGI worker 1
121.00MB (1.48%) 123900 neutron-openvswitch-agent ...
119.50MB (1.46%) 122368 cinder-apiuWSGI worker 1
---(snip)---
* `free -m` output
total used free shared buff/cache available
Mem: 7955 7427 196 16 331 219
Swap: 1022 1019 3
[2]: http://eavesdrop.openstack.org/irclogs/%23openstack-infra/
%23openstack-infra.2020-11-25.log.html
Change-Id: I030ffd5fd11b7ca9abca56e85e449ed4c4d709bd
578b12e989