Consistent data

5. Keeping your data set consistent

5.1 Fixing broken refs

Occasionally when you are working on setting up the relationships between recs in a station, you will delete a Component that has other Components referencing it. For instance, in the example in 4.4, if we delete "TrashCompactor", then both of our BooleanWritables will have an invalid equipRef.

To fix this problem, there is an action on NHaystackService called removeBrokenRefs that you can invoke. This action deletes all of the refs in the station that do not reference a valid rec. Each time a broken ref is deleted, a message is also generated in the station log telling you which Component was fixed.

In a future version of NHaystack, there will be a view on NHaystackService that will make it easier for you to find the broken refs and fix them.

5.2 Using TimeZone Aliases

Sometimes an N4 TimeZone (a.k.a BTimeZone) do not map cleanly into a Haystack TimeZone (a.k.a HTimeZone). This happens when the BTimeZone uses an offset-style TimeZone ID, like "GMT-05:00", rather than a valid Olson ID, like "America/New_York". When this occurs, you will see errors in your log output that look like this:

ERROR [11:59:01 04-May-13 GMT-05:00][nhaystack] Cannot create tz tag: Unknown tz: GMT-05:00

In cases like this, NHaystack simply omits the tz tag for the historized point in question.

However, NHaystack also allows you to provide a custom mapping that overcomes this problem, via the "timeZoneAliases" folder on your BHaystackService. Go to the nhaystack palette in Workbench, drag a "timeZoneAlias" onto the "timeZoneAliases" folder, and configure it so that the bogus N4 TimeZone ID, like "GMT-05:00", is mapped onto a proper HTimezone, such as "America/New_York". Now when NHaystack is attempting to generate the tz tag, it will know how to proceed when it encounters non-Olson timezones.

In a future version of NHaystack, there will be a view on NHaystackService that will help you find which timezones are invalid in your dataset, but for now you must go through your log output, find the "Cannot create tz tag" error messages, and copy-and-paste the offending TimeZone ID into a timeZoneAlias that maps onto the 'real' HTimezone.

Note that if the machine that you are running Workbench from is mis-configured, it will provide a default HTimeZone of the form "Etc/GMT-5" in your timeZoneAlias. You should not use the HTimeZones from the "Etc" region unless you are really sure of what you are doing. Instead, always use the proper geographic region-and-timezone, like "America/New_York".