56ae2db7ac
The common role was previously added as a dependency to all other roles. It would set a fact after running on a host to avoid running twice. This had the nice effect that deploying any service would automatically pull in the common services for that host. When using tags, any services with matching tags would also run the common role. This could be both surprising and sometimes useful. When using Ansible at large scale, there is a penalty associated with executing a task against a large number of hosts, even if it is skipped. The common role introduces some overhead, just in determining that it has already run. This change extracts the common role into a separate play, and removes the dependency on it from all other roles. New groups have been added for cron, fluentd, and kolla-toolbox, similar to other services. This changes the behaviour in the following ways: * The common role is now run for all hosts at the beginning, rather than prior to their first enabled service * Hosts must be in the necessary group for each of the common services in order to have that service deployed. This is mostly to avoid deploying on localhost or the deployment host * If tags are specified for another service e.g. nova, the common role will *not* automatically run for matching hosts. The common tag must be specified explicitly The last of these is probably the largest behaviour change. While it would be possible to determine which hosts should automatically run the common role, it would be quite complex, and would introduce some overhead that would probably negate the benefit of splitting out the common role. Partially-Implements: blueprint performance-improvements Change-Id: I6a4676bf6efeebc61383ec7a406db07c7a868b2a |
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