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44 lines
2.2 KiB
Markdown
44 lines
2.2 KiB
Markdown
# AWX as an Ansible Fact Cache
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AWX can store and retrieve per-host facts via an Ansible Fact Cache Plugin.
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This behavior is configurable on a per-job-template basis. When enabled, AWX
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will serve fact requests for all Hosts in an Inventory related to the Job
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running. This allows users to use Job Templates with `--limit` while still
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having access to the entire Inventory of Host facts.
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## AWX Fact Cache Implementation Details
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### AWX Injection
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In order to understand the behavior of AWX as a fact cache, you will need to
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understand how fact caching is achieved in AWX. When a Job launches with
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`use_fact_cache=True`, AWX will write all `ansible_facts` associated with
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each Host in the associated Inventory as JSON files on the local file system
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(one JSON file per host). Jobs invoked with `use_fact_cache=False` will not
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write `ansible_facts` files.
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### Ansible Plugin Usage
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When `use_fact_cache=True`, Ansible will be configured to use the `jsonfile`
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cache plugin. Any `get()` call to the fact cache interface in Ansible will
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result in a JSON file lookup for the host-specific set of facts. Any `set()`
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call to the fact cache will result in a JSON file being written to the local
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file system.
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### AWX Cache to DB
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When a Job with `use_fact_cache=True` finishes running, AWX will look at all
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of the local JSON files that represent the fact data. Any records with file
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modification times that have increased (because Ansible updated the file via
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`cache.set()`) will result in the latest value being saved to the database. On
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subsequent playbook runs, AWX will _only_ inject cached facts that are _newer_
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than `settings.ANSIBLE_FACT_CACHE_TIMEOUT` seconds.
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## AWX Fact Logging
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New and changed facts will be logged via AWX's logging facility, specifically
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to the `system_tracking` namespace or logger. The logging payload will include
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the fields `host_name`, `inventory_id`, and `ansible_facts`. Where
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`ansible_facts` is a dictionary of all Ansible facts for `host_name` in AWX
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Inventory `inventory_id`.
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## Integration Testing
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* Ensure `clear_facts` sets `hosts/<id>/ansible_facts` to `{}`.
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* Ensure that `gather_facts: False` does NOT result in clearing existing facts.
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* Ensure that when a host fact timeout is reached, that the facts are not used from the cache.
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