You need to find a set of line in the trace like this
[2019-08-24T16:02:30,115][TRACE][filewatch.sincedbcollection] open: reading from /dev/null
[2019-08-24T16:02:30,140][TRACE][filewatch.sincedbcollection] open: count of keys read: 0
[2019-08-24T16:02:30,322][TRACE][filewatch.discoverer ] discover_files {"count"=>1}
[2019-08-24T16:02:30,520][TRACE][filewatch.discoverer ] discover_files handling: {"new discovery"=>true, "watched_file details"=> ...
[2019-08-24T16:02:30,557][TRACE][filewatch.sincedbcollection] associate: finding {"inode"=>"12714756", "path"=>"/home/foo.txt"}
[2019-08-24T16:02:30,565][TRACE][filewatch.sincedbcollection] associate: unmatched
[2019-08-24T16:02:30,774][TRACE][filewatch.tailmode.processor] Delayed Delete processing
[2019-08-24T16:02:30,802][TRACE][filewatch.tailmode.processor] Watched + Active restat processing
[2019-08-24T16:02:30,885][TRACE][filewatch.tailmode.processor] Rotation In Progress processing
[2019-08-24T16:02:30,914][TRACE][filewatch.tailmode.processor] Watched processing
[2019-08-24T16:02:30,933][TRACE][filewatch.tailmode.handlers.createinitial] handling: foo.txt
[2019-08-24T16:02:30,994][TRACE][filewatch.tailmode.handlers.createinitial] opening foo.txt
[2019-08-24T16:02:31,087][TRACE][filewatch.tailmode.handlers.createinitial] handle_specifically opened file handle: 85, path: foo.txt
[2019-08-24T16:02:31,175][TRACE][filewatch.tailmode.handlers.createinitial] add_new_value_sincedb_collection ...
[2019-08-24T16:02:31,242][TRACE][filewatch.tailmode.processor] Active - file grew: foo.txt: new size is 677, bytes read 0
[2019-08-24T16:02:31,249][TRACE][filewatch.tailmode.handlers.grow] handling: foo.txt
[2019-08-24T16:02:31,293][TRACE][filewatch.tailmode.handlers.grow] reading... {"iterations"=>1, "amount"=>677, "filename"=>"foo.txt"}
[2019-08-24T16:02:31,306][DEBUG][filewatch.tailmode.handlers.grow] read_to_eof: get chunk
[2019-08-24T16:02:31,356][DEBUG][logstash.inputs.file ] Received line