Capture unmatched lines

lib/fluent/plugin/in_tail.rb

@@ -65,6 +65,8 @@ def initialize
     config_param :read_lines_limit, :integer, default: 1000
     desc 'The interval of flushing the buffer for multiline format'
     config_param :multiline_flush_interval, :time, default: nil
+    desc 'Enable the option to emit unmatched lines.'
+    config_param :emit_unmatched_lines, :bool, default: false
     desc 'Enable the additional watch timer.'
     config_param :enable_watch_timer, :bool, default: true
     desc 'The encoding after conversion of the input.'
@@ -357,6 +359,11 @@ def convert_line_to_event(line, es, tail_watcher)
             record[@path_key] ||= tail_watcher.path unless @path_key.nil?
             es.add(time, record)
           else
+            if @emit_unmatched_lines
+              record = {'unmatched_line' => line}
+              record[@path_key] ||= tail_watcher.path unless @path_key.nil?
+              es.add(Fluent::EventTime.now, record)
+            end
             log.warn "pattern not match: #{line.inspect}"
           end
         }
@@ -387,6 +394,9 @@ def parse_multilines(lines, tail_watcher)
             lb = line
           else
             if lb.nil?
+              if @emit_unmatched_lines
+                convert_line_to_event(line, es, tail_watcher)
+              end
               log.warn "got incomplete line before first line from #{tail_watcher.path}: #{line.inspect}"
             else
               lb << line

test/plugin/test_in_tail.rb

@@ -149,6 +149,28 @@ def test_emit(data)
       assert_equal(1, d.emit_count)
     end
 
+    def test_emit_with_emit_unmatched_lines_true
+      config = config_element("", "", { "format" => "/^(?<message>test.*)/", "emit_unmatched_lines" => true })
+      File.open("#{TMP_DIR}/tail.txt", "wb") { |f| }
+
+      d = create_driver(config)
+      d.run(expect_emits: 1) do
+        File.open("#{TMP_DIR}/tail.txt", "ab") {|f|
+          f.puts "test line 1"
+          f.puts "test line 2"
+          f.puts "bad line 1"
+          f.puts "test line 3"
+        }
+      end
+
+      events = d.events
+      assert_equal(4, events.length)
+      assert_equal({"message" => "test line 1"}, events[0][2])
+      assert_equal({"message" => "test line 2"}, events[1][2])
+      assert_equal({"unmatched_line" => "bad line 1"}, events[2][2])
+      assert_equal({"message" => "test line 3"}, events[3][2])
+    end
+
     data('flat 1' => [:flat, 1, 2],
          'flat 10' => [:flat, 10, 1],
          'parse 1' => [:parse, 1, 2],
@@ -516,6 +538,35 @@ def test_multiline(data)
       assert_equal({"message1" => "test8"}, events[3][2])
     end
 
+    data(flat: MULTILINE_CONFIG,
+         parse: PARSE_MULTILINE_CONFIG)
+    def test_multiline_with_emit_unmatched_lines_true(data)
+      config = data + config_element("", "", { "emit_unmatched_lines" => true })
+      File.open("#{TMP_DIR}/tail.txt", "wb") { |f| }
+
+      d = create_driver(config)
+      d.run(expect_emits: 1) do
+        File.open("#{TMP_DIR}/tail.txt", "ab") { |f|
+          f.puts "f test1"
+          f.puts "s test2"
+          f.puts "f test3"
+          f.puts "f test4"
+          f.puts "s test5"
+          f.puts "s test6"
+          f.puts "f test7"
+          f.puts "s test8"
+        }
+      end
+
+      events = d.events
+      assert_equal(5, events.length)
+      assert_equal({"unmatched_line" => "f test1"}, events[0][2])
+      assert_equal({"message1" => "test2", "message2" => "test3", "message3" => "test4"}, events[1][2])
+      assert_equal({"message1" => "test5"}, events[2][2])
+      assert_equal({"message1" => "test6", "message2" => "test7"}, events[3][2])
+      assert_equal({"message1" => "test8"}, events[4][2])
+    end
+
     data(flat: MULTILINE_CONFIG,
          parse: PARSE_MULTILINE_CONFIG)
     def test_multiline_with_flush_interval(data)