bfc4354905
One way to improve the performance of Ansible is through fact caching.
Rather than gather facts in every play, we can configure Ansible to
cache them in a persistent store. An example Ansible configuration for
doing this is as follows:
[defaults]
gathering = smart
fact_caching = jsonfile
fact_caching_connection = ./facts
fact_caching_timeout = 86400
This does not affect Kolla Ansible however, since we use the setup
module which unconditionally gathers facts regardless of the state of
the cache. This gets worse with large inventories limited to a small
batch of hosts via --limit or serial, since the limited hosts must
gather facts for all others.
One way to detect whether facts exist for a host is via the
'module_setup' variable, which exists only when facts exist. This change
uses the 'module_setup' fact to determine whether facts need to be
gathered for hosts outside of the batch. For hosts in the batch, we
switch from using the setup module to gather_facts on the play, which
can use the 'smart' gathering logic.
Change-Id: I04841fb62b2e1d9e97ce4b75ce3a7349b9c74036
Partially-Implements: blueprint performance-improvements
(cherry picked from commit e0ba55a85d)
41 lines
1.6 KiB
YAML
41 lines
1.6 KiB
YAML
---
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# NOTE(awiddersheim): Gather facts for all hosts as a
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# first step since several plays below require them when
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# building their configurations.
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- name: Gather facts for all hosts
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hosts: all
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serial: '{{ kolla_serial|default("0") }}'
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gather_facts: true
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tasks:
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- name: Group hosts to determine when using --limit
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group_by:
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key: "all_using_limit_{{ (ansible_play_batch | length) != (groups['all'] | length) }}"
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tags: always
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# NOTE(pbourke): This case covers deploying subsets of hosts using --limit. The
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# limit arg will cause the first play to gather facts only about that node,
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# meaning facts such as IP addresses for rabbitmq nodes etc. will be undefined
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# in the case of adding a single compute node.
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# NOTE(mgoddard): Divide all hosts to be queried between the hosts selected via
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# the limit.
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- name: Gather facts for all hosts (if using --limit)
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hosts: all_using_limit_True
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serial: '{{ kolla_serial|default("0") }}'
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gather_facts: false
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vars:
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batch_index: "{{ ansible_play_batch.index(inventory_hostname) }}"
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batch_size: "{{ ansible_play_batch | length }}"
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# Use a python list slice to divide the group up.
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# Syntax: [<start index>:<end index>:<step size>]
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delegate_hosts: "{{ groups['all'][batch_index | int::batch_size | int] }}"
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tasks:
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- name: Gather facts
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setup:
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delegate_facts: True
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delegate_to: "{{ item }}"
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with_items: "{{ delegate_hosts }}"
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# We gathered facts for all hosts in the batch during the first play.
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when:
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- not hostvars[item].module_setup | default(false)
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tags: always
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