*: if we have two instances of the same DAG running at the same time (or any two DAG instances whose node jobs share user log files), things will get goofed up because the submit event notes only contain the node name; there's no way to tell which DAG the event goes with if they both have nodes with the given name *: possible confusion in recovery mode when going from DST to standard time, because timestamps are in local time *: ReadMultipleUserLogs class vs. MultiLogFiles class +*: 1-sec sleeps before submits to make sure we can unambiguously order events when reading them back (because the user log timestamps only have a resolution of 1 sec)
