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The mapping from compose-style `docker_restart_policy` (`no`,
`on-failure[:N]`, `always`, `unless-stopped`) to swarm's
`deploy.restart_policy.condition` (`none`, `on-failure`, `any`) was
seven lines of inline Jinja `{% set / if / elif / else %}` in
`roles/sys-svc-container/templates/deploy.yml.j2`. That made the
template noisy at the call site, hid the typo-safety logic from
unit tests, and forced every reviewer to re-derive the mapping table
from a chain of conditionals.
Move the mapping into a dedicated filter plugin so the call site is
a single readable expression and the mapping is exercised by a
focused test suite.
- plugins/filter/swarm_restart_condition.py: pure function, no Jinja
context dependency (the input is the only thing that matters).
Strips + str-casts the input so YAML-literal slop like `" no "`
or a numeric `0` does not defeat the mapping. Output is always a
member of the closed swarm condition set `{none, on-failure, any}`;
unknown / typo inputs map to `any` (safe default -- a misconfigured
long-running service still runs and the operator notices the typo
via the literal `condition: any` in the rendered file, instead of
silently degrading to `none` which would skip respawning a real
service).
- tests/unit/plugins/filter/test_swarm_restart_condition.py: 12
cases. Direct mapping per branch, `on-failure:N` suffix form
(suffix dropped because swarm carries max-attempts in a separate
`max_attempts` key), None / empty / whitespace fallback,
stringification of non-string input, strip semantics, an explicit
unknown-value test that pins the safe-default rationale, and a
property test over twelve inputs that asserts the output is always
inside the closed swarm condition set. A second test class
verifies the filter is registered under the exact name
`swarm_restart_condition` so a typo in the FilterModule shim does
not silently fall back to the identity filter.
- roles/sys-svc-container/templates/deploy.yml.j2: thirteen lines of
inline Jinja (`{% set _drp = … %}` + four `{% set
_swarm_restart_condition = … %}` branches) collapse to a single
filter expression:
condition: {{ docker_restart_policy
| default(DOCKER_RESTART_POLICY)
| swarm_restart_condition }}
The runtime mapping is identical to the pre-refactor inline
version (verified by the new unit tests against the same input
buckets), so nothing changes for existing roles.
Custom Filter Plugins for Infinito.Nexus
This directory contains custom Ansible filter plugins used within the Infinito.Nexus project.
When to Use a Filter Plugin
- Transform values: Use filters to transform, extract, reformat, or compute values from existing variables or facts.
- Inline data manipulation: Filters are designed for inline use in Jinja2 expressions (in templates, tasks, vars, etc.).
- No external lookups: Filters only operate on data you explicitly pass to them and cannot access external files, the Ansible inventory, or runtime context.
Examples
{{ role_name | get_entity_name }}
{{ my_list | unique }}
{{ user_email | regex_replace('^(.+)@.*$', '\\1') }}
When not to Use a Filter Plugin
- If you need to load data from an external source (e.g., file, environment, API), use a lookup plugin instead.
- If your logic requires access to inventory, facts, or host-level information that is not passed as a parameter.