added path_key to include read path into the event under this key

lib/fluent/plugin/in_tail.rb

@@ -25,6 +25,7 @@ def initialize
     end
 
     config_param :path, :string
+    config_param :path_key, :string, :default => nil
     config_param :tag, :string
     config_param :rotate_wait, :time, :default => 5
     config_param :pos_file, :string, :default => nil
@@ -126,11 +127,12 @@ def parse_line(line)
       return @parser.parse(line)
     end
 
-    def convert_line_to_event(line, es)
+    def convert_line_to_event(line, es, tail_watcher)
       begin
         line.chomp!  # remove \n
         time, record = parse_line(line)
         if time && record
+          record[@path_key] ||= tail_watcher.path unless @path_key.nil?
           es.add(time, record)
         else
           log.warn "pattern not match: #{line.inspect}"
@@ -144,7 +146,7 @@ def convert_line_to_event(line, es)
     def parse_singleline(lines, tail_watcher)
       es = MultiEventStream.new
       lines.each { |line|
-        convert_line_to_event(line, es)
+        convert_line_to_event(line, es, tail_watcher)
       }
       es
     end
@@ -155,7 +157,7 @@ def parse_multilines(lines, tail_watcher)
       lines.each { |line|
         if @parser.parser.firstline?(line)
           if lb
-            convert_line_to_event(lb, es)
+            convert_line_to_event(lb, es, tail_watcher)
           end
           lb = line
         else

test/plugin/in_tail.rb

@@ -203,4 +203,31 @@ def test_multilinelog_with_multiple_paths
     assert_equal({"message" => "test4"}, emits[2][2])
     assert_equal({"message" => "test4"}, emits[3][2])
   end
+
+  def test_path_key
+    File.open("#{TMP_DIR}/tail.txt", "w") { |f| }
+
+    d = create_driver(%[
+      path #{TMP_DIR}/tail.txt
+      tag t1
+      format /(?<message>.*)/
+      path_key path
+    ], false)
+
+    d.run do
+      sleep 1
+
+      File.open("#{TMP_DIR}/tail.txt", "a") {|f|
+        f.puts "test1"
+        f.puts "test2"
+      }
+      sleep 1
+    end
+
+    emits = d.emits
+    assert_equal(true, emits.length > 0)
+    assert_equal({"message"=>"test1", "path"=>"#{TMP_DIR}/tail.txt"}, emits[0][2])
+    assert_equal({"message"=>"test2", "path"=>"#{TMP_DIR}/tail.txt"}, emits[1][2])
+  end
+
 end