Log the situation when resolving the ILM template settings.

Author: mashhurs

lib/logstash/outputs/elasticsearch/template_manager.rb

@@ -54,19 +54,27 @@ def self.add_ilm_settings_to_template(plugin, template)
     end
 
     def self.resolve_template_settings(plugin, template)
-      return composable_index_template_settings(template) if template.key?('template')
-      return legacy_index_template_settings(template) if template.key?('settings')
-      return template_endpoint(plugin) == INDEX_TEMPLATE_ENDPOINT ?
-               composable_index_template_settings(template) :
-               legacy_index_template_settings(template)
+      if template.key?('template')
+        plugin.logger.trace("Resolving ILM template settings: under 'template' key", :template => template, :template_api => plugin.template_api, :es_version => plugin.maximum_seen_major_version)
+        composable_index_template_settings(template)
+      elsif template.key?('settings')
+        plugin.logger.trace("Resolving ILM template settings: under 'settings' key", :template => template, :template_api => plugin.template_api, :es_version => plugin.maximum_seen_major_version)
+        legacy_index_template_settings(template)
+      else
+        template_endpoint = template_endpoint(plugin)
+        plugin.logger.trace("Resolving ILM template settings: template doesn't have 'settings' or 'template' fields, falling back to auto detection", :template => template, :template_api => plugin.template_api, :es_version => plugin.maximum_seen_major_version, :template_endpoint => template_endpoint)
+        template_endpoint == INDEX_TEMPLATE_ENDPOINT ?
+          composable_index_template_settings(template) :
+          legacy_index_template_settings(template)
+      end
     end
 
-    # Returns (if exists) or creates _template API compatible template settings
+    # Sets ['settings'] field to be compatible with _template API structure
     def self.legacy_index_template_settings(template)
       template['settings'] ||= {}
     end
 
-    # Returns (if exists) or creates _index_template API compatible template settings
+    # Sets the ['template']['settings'] fields if not exist to be compatible with _index_template API structure
     def self.composable_index_template_settings(template)
       template['template'] ||= {}
       template['template']['settings'] ||= {}

spec/unit/outputs/elasticsearch/template_manager_spec.rb

@@ -73,6 +73,7 @@
         let(:template_api) { "composable" }
 
         it 'resolves composable index template API compatible setting' do
+          expect(plugin).to receive(:maximum_seen_major_version).at_least(:once).and_return(8) # required to log
           template = {}
           described_class.resolve_template_settings(plugin, template)
           expect(template["template"]["settings"]).not_to eq(nil)
@@ -83,6 +84,7 @@
         let(:template_api) { "legacy" }
 
         it 'resolves legacy index template API compatible setting' do
+          expect(plugin).to receive(:maximum_seen_major_version).at_least(:once).and_return(7) # required to log
           template = {}
           described_class.resolve_template_settings(plugin, template)
           expect(template["settings"]).not_to eq(nil)