Add custom Ansible filters

Author: Alex-Welsh

etc/kayobe/ansible.cfg

@@ -10,6 +10,8 @@ inject_facts_as_vars = False
 callbacks_enabled = ansible.posix.profile_tasks
 # Silence warning about invalid characters found in group names
 force_valid_group_names = ignore
+# Default value plus custom filter plugins path
+filter_plugins = $ANSIBLE_HOME/plugins/filter:/usr/share/ansible/plugins/filter:$KAYOBE_CONFIG_PATH/ansible/filter_plugins/
 
 [inventory]
 # Fail when any inventory source cannot be parsed.

etc/kayobe/ansible/filter_plugins/filters.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+from ansible.errors import AnsibleFilterError
+from ansible.plugins.filter.core import to_bool
+
+class FilterModule(object):
+    def filters(self):
+        return {
+            'select_enabled': self.select_enabled
+        }
+
+    def select_enabled(self, items: list[dict], key: str = 'items') -> list:
+        """Filters a list of dictionaries to select enabled items.
+
+        Parameters:
+            items:
+                List of dictionaries - Each item contains an 'enabled' key, and
+                a key matching the "key" parameter.
+            key:
+                String - The key in each dictionary to extract when 'enabled'
+                is true.
+        
+        Returns:
+            A list of values from the specified key in each dictionary where
+            'enabled' is true. List values are flattened.
+        """
+        result = []
+        for item in items:
+            try:
+                if to_bool(item["enabled"]):
+                    result += item[key] if isinstance(item[key], list) else [item[key]]
+            except KeyError as e:
+                raise AnsibleFilterError("Key %s not found in item: %s" % (e, item))
+        return result

etc/kayobe/kolla/inventory/group_vars/prometheus-blackbox-exporter

@@ -6,16 +6,7 @@
 # prometheus_blackbox_exporter_endpoints_kayobe is another set of default
 # endpoints that are templated by Kayobe rather than Kolla Ansible. See
 # kolla/globals.yml for more details.
-prometheus_blackbox_exporter_endpoints_custom: |
-  {% set endpoints = [] %}
-  {% for dict_item in (prometheus_blackbox_exporter_endpoints_kayobe | default([]) + stackhpc_prometheus_blackbox_exporter_endpoints_default) %}
-  {% if dict_item.enabled | bool %}
-  {% for endpoint in dict_item.endpoints %}
-  {% set _ = endpoints.append(endpoint) %}
-  {% endfor %}
-  {% endif %}
-  {% endfor %}
-  {{ (endpoints + stackhpc_prometheus_blackbox_exporter_endpoints_custom) | unique | select | list }}
+prometheus_blackbox_exporter_endpoints_custom: "{{ ((prometheus_blackbox_exporter_endpoints_kayobe | default([]) + stackhpc_prometheus_blackbox_exporter_endpoints_default) | select_enabled('endpoints') + stackhpc_prometheus_blackbox_exporter_endpoints_custom) | unique | select | list }}"
 
 # A list of custom prometheus Blackbox exporter endpoints. Each element should
 # have the following format:

releasenotes/notes/custom-ansible-filters-bad99d417495b7e0.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    Added a new file ``filters.py`` containing custom Ansible filters.
+    Custom filters can be used to replace complex jinja expressions with
+    simplified python code. The first filter ``select_enabled`` replaces
+    an expression to template Blackbox Exporter endpoints. It also serves as an
+    example for future filters.