in_http: Honor keep_time_key parameter in batch mode.

The in_http plugin supports "batch" mode for sending multiple events in
a single HTTP request. The problem is that in_http does not honor the
`keep_time_key` option when processing those bulk-insertion requests.

This means that "time" key in each record gets discarded unconditionally
in batch mode. For example, the following request:

    $ curl -d '[{"time":1514736000,"key":"foo"}]' http://localhost/

will produces a log record:

    2018-01-01 01:00:00.000000000 +0900 : {"key":"foo"}

even if the `keep_time_key` option is enabled.

This patch fixes this issue by teaching in_http to honor the option
value of its parser plugin instance.

Signed-off-by: Fujimoto Seiji <[email protected]>

lib/fluent/plugin/in_http.rb

@@ -202,11 +202,17 @@ def on_request(path_info, params)
             if @add_remote_addr
               single_record['REMOTE_ADDR'] = params['REMOTE_ADDR']
             end
-            single_time = if t = single_record.delete('time')
-                            Fluent::EventTime.from_time(Time.at(t))
-                          else
-                            time
-                          end
+
+            if single_record.has_key?('time')
+                single_time = Fluent::EventTime.from_time(Time.at(single_record['time']))
+            else
+                single_time = time
+            end
+
+            unless @parser and @parser.keep_time_key
+                single_record.delete('time')
+            end
+
             mes.add(single_time, single_record)
           end
           router.emit_stream(tag, mes)