Support configuration of custom fluentd filters

In some scenarios it may be useful to apply custom filters to logs
before forwarding them.  This may be useful to add additional tags to
the messages or to modify the tags to conform to a log format that
differs from the one defined by kolla-ansible.

Configuration of custom fluentd filters is possible by placing filter
configuration files in ``/etc/kolla/config/fluentd/filter/*.conf`` on
the ansible control host.

Change-Id: I29a20efb0df4bf3564ef009616c786e928aa26d9
Implements: blueprint fluentd-custom-filters

ansible/roles/common/handlers/main.yml

@@ -21,6 +21,7 @@
       or fluentd_output_custom.changed | bool
       or fluentd_format.changed | bool
       or fluentd_filter.changed | bool
+      or fluentd_filter_custom.changed | bool
       or fluentd_td_agent.changed | bool
       or fluentd_container.changed | bool
 

ansible/roles/common/tasks/config.yml

@@ -117,6 +117,23 @@
   notify:
     - Restart fluentd container
 
+- name: Find custom fluentd filter config files
+  local_action:
+    module: find
+    path: "{{ node_custom_config }}/fluentd/filter"
+    pattern: "*.conf"
+  run_once: True
+  register: find_custom_fluentd_filters
+
+- name: Copying over custom fluentd filter config files
+  template:
+    src: "{{ item.path }}"
+    dest: "{{ node_config_directory }}/fluentd/filter/{{ item.path | basename }}"
+  register: fluentd_filter_custom
+  with_items: "{{ find_custom_fluentd_filters.files }}"
+  notify:
+    - Restart fluentd container
+
 - name: Copying over td-agent.conf
   template:
     src: "td-agent.conf.j2"

ansible/roles/common/templates/fluentd.json.j2

@@ -47,15 +47,11 @@
             "owner": "{{ fluentd_user }}",
             "perm": "0600"
         },
+        {# Copy all configuration files in filter/ directory to include #}
+        {# custom filter configs. #}
         {
-            "source": "{{ container_config_directory }}/filter/00-record_transformer.conf",
-            "dest": "{{ fluentd_dir }}/filter/00-record_transformer.conf",
-            "owner": "{{ fluentd_user }}",
-            "perm": "0600"
-        },
-        {
-            "source": "{{ container_config_directory }}/filter/01-rewrite.conf",
-            "dest": "{{ fluentd_dir }}/filter/01-rewrite.conf",
+            "source": "{{ container_config_directory }}/filter/*.conf",
+            "dest": "{{ fluentd_dir }}/filter/",
             "owner": "{{ fluentd_user }}",
             "perm": "0600"
         },

doc/source/reference/central-logging-guide.rst

@@ -155,6 +155,18 @@ can also be exported at once by choosing *export everything* option.
 In the same tab (Settings - Objects) one can also import saved items by
 choosing *import* option.
 
+Custom log filtering
+====================
+
+In some scenarios it may be useful to apply custom filters to logs before
+forwarding them.  This may be useful to add additional tags to the messages
+or to modify the tags to conform to a log format that differs from the one
+defined by kolla-ansible.
+
+Configuration of custom fluentd filters is possible by placing filter
+configuration files in ``/etc/kolla/config/fluentd/filter/*.conf`` on the
+control host.
+
 Custom log forwarding
 =====================
 

releasenotes/notes/fluentd-custom-filter-config-26ee8801c7782b08.yaml

+---
+features:
+  - |
+    Adds ability to configure custom fluentd filters.
+
+    In some scenarios it may be useful to apply custom filters to logs before
+    forwarding them.  This may be useful to add additional tags to the messages
+    or to modify the tags to conform to a log format that differs from the one
+    defined by kolla-ansible.
+
+    Configuration of custom fluentd filters is possible by placing filter
+    configuration files in ``/etc/kolla/config/fluentd/filter/*.conf`` on the
+    control host.