Merge pull request #30 from repeatedly/support-prepare-values

Support prepare_value

Author: repeatedly

README.md

@@ -62,6 +62,20 @@ But unlike `record_transformer`, `record_modifier` doesn't support following fea
 - tag_suffix and tag_prefix
 - dynamic key placeholder
 
+### prepare_value
+
+Prepare values for filtering. This ruby code is evaluated in `configure` phase and prepared values can be used in `<record>`. Here is an example:
+
+    <filter pattern>
+      @type record_modifier
+      prepare_value require 'foo'; @foo = Foo.new
+      <record>
+        key ${@foo.method1}
+      </record>
+    </filter>
+
+This feature is useful for using external library.
+
 ### char_encoding
 
 Fluentd including some plugins treats logs as a BINARY by default to forward.

lib/fluent/plugin/filter_record_modifier.rb

@@ -4,6 +4,11 @@ module Fluent
   class Plugin::RecordModifierFilter < Plugin::Filter
     Fluent::Plugin.register_filter('record_modifier', self)
 
+    config_param :prepare_value, :string, default: nil,
+                 desc: <<-DESC
+Prepare values for filtering in configure phase. Prepared values can be used in <record>.
+You can write any ruby code.
+DESC
     config_param :char_encoding, :string, default: nil,
                  desc: <<-DESC
 Fluentd including some plugins treats the logs as a BINARY by default to forward.
@@ -26,7 +31,7 @@ class Plugin::RecordModifierFilter < Plugin::Filter
 This option is exclusive with `remove_keys`.
 DESC
 
-    BUILTIN_CONFIGURATIONS = %W(type @type log_level @log_level id @id char_encoding remove_keys whitelist_keys)
+    BUILTIN_CONFIGURATIONS = %W(type @type log_level @log_level id @id char_encoding remove_keys whitelist_keys prepare_value)
 
     def configure(conf)
       super
@@ -68,7 +73,7 @@ def configure(conf)
           check_config_placeholders(k, v)
           element.has_key?(k) # to suppress unread configuration warning
           @has_tag_parts = true if v.include?('tag_parts')
-          @map[k] = DynamicExpander.new(k, v)
+          @map[k] = DynamicExpander.new(k, v, @prepare_value)
         end
       end
 
@@ -157,7 +162,7 @@ def check_config_placeholders(k, v)
     end
 
     class DynamicExpander
-      def initialize(param_key, param_value)
+      def initialize(param_key, param_value, prepare_value)
         if param_value.include?('${')
           __str_eval_code__ = parse_parameter(param_value)
 
@@ -173,6 +178,12 @@ def expand(tag, time, record, tag_parts)
           @param_value = param_value
         end
 
+        begin
+          eval prepare_value if prepare_value
+        rescue SyntaxError
+          raise ConfigError, "Pass invalid syntax parameter : key = prepare_value, value = #{prepare_value}"
+        end
+
         begin
           # check eval genarates wrong code or not
           expand(nil, nil, nil, nil)

test/test_filter_record_modifier.rb

@@ -126,6 +126,21 @@ def test_remove_non_whitelist_keys
     assert_equal [{"k1" => 'v', "k2" => 'v'}], d.filtered.map(&:last)
   end
 
+  def test_prepare_values
+    d = create_driver %[
+      prepare_value @foo = 'foo'
+      <record>
+        test_key ${@foo}
+      </record>
+    ]
+
+    d.run(default_tag: @tag) do
+      d.feed("k1" => 'v')
+    end
+
+    assert_equal [{"k1" => 'v', "test_key" => 'foo'}], d.filtered.map(&:last)
+  end
+
   sub_test_case 'frozen check' do
     def test_set_char_encoding
       d = create_driver %[