I find the original log line useful to keep

Author: Pablo Brasero

lib/heroku-log-parser.rb

@@ -63,6 +63,7 @@ def event_data(matching)
       event[:msg_id] = interpret_nil(nil)
       event[:structured_data] = interpret_nil(matching[7])
       event[:message] = interpret_nil(matching[8])
+      event[:original] = matching[0]
       event
     end
 

test/heroku_log_parser_test.rb

@@ -16,6 +16,7 @@
       msg_id: nil,
       structured_data: nil,
       message: "Starting process with command `bundle exec rackup config.ru -p 24405`",
+      original: "<40>1 2012-11-30T06:45:26+00:00 heroku web.3 d.73ea7440-270a-435a-a0ea-adf50b4e5f5a - Starting process with command `bundle exec rackup config.ru -p 24405`",
     }]
     assert_equal expected, actual
   end
@@ -34,6 +35,7 @@
       msg_id: nil,
       structured_data: nil,
       message: "- Started GET \"/2013/02/26/full-text-search-in-your-browser\" for 197.112.207.103 at 2014-07-17 12:59:25 +0000",
+      original: "<190>1 2014-07-17T12:59:25.223980+00:00 d.8f7a4b11-c323-c764-a74f-89bf4c1100ab app web.2 - - Started GET \"/2013/02/26/full-text-search-in-your-browser\" for 197.112.207.103 at 2014-07-17 12:59:25 +0000",
     }, {
       priority: 190,
       syslog_version: 1,
@@ -44,6 +46,7 @@
       msg_id: nil,
       structured_data: nil,
       message: "- Started GET \"/blog.rss\" for 54.219.13.100 at 2014-07-18 12:59:25 +0000",
+      original: "<190>1 2014-07-17T12:59:25.239432+00:00 d.8f7a4b11-c323-c764-a74f-89bf4c1100ab app web.1 - - Started GET \"/blog.rss\" for 54.219.13.100 at 2014-07-18 12:59:25 +0000",
     }]
     assert_equal expected, actual
   end