[thredds] Problem with time variable in FMRC "Best" collection

• To: "thredds@xxxxxxxxxxxxxxxx" <thredds@xxxxxxxxxxxxxxxx>
• Subject: [thredds] Problem with time variable in FMRC "Best" collection
• From: Tor Nordam <Tor.Nordam@xxxxxxxxx>
• Date: Mon, 15 Dec 2014 15:31:43 +0000

Hi,

I'm trying to set up a Forecast Model Run Collection using THREDDS. I have a 
collection of netCDF files, where the time at which the simulation was run is 
part of the filename:

forecast_yyMMddHHmm.nc

In the files, the time variable is an integer, and gives time as number of 
hours since a given date. This date is the same in all my files. Since the 
times are given in integer hours, there should be absolutely no uncertainty as 
to whether two timesteps are the same.

However, when the THREDDS server presents this as an FMRC using the "best" 
model (for a given timpstep, it always serves data from the most recently 
performed simulation), it converts the time variable to a double, and somehow 
manages to present some timesteps which are actually the same as slightly 
different. For example, all of these are actually the same in my data, yet are 
presented as three different timesteps:

-65.10000033333334, -65.10000033333333, -65.1

The reason that the numbers are not whole hours is that the server also changes 
the reference point for the time axis from that specified in my files, to the 
simulation run time of the first file. This is fair enough, if only the data 
would be presented correctly.

Interestingly, if I restart the thredds server, it manages to read and 
correctly present the files that are there at the time of restart, but later 
on, if it does a rescan triggered by the cron expression in the xml file, it 
doesn't get the timesteps right.

Any suggestions as to what I'm doing wrong?

The dataset definition in the xml-file looks like this:

  <dataset name="FMRC Example">
    <featureCollection name="BOM" featureType="FMRC" harvest="true" path="BOM">
      <metadata inherited="true">
        <serviceName>fmrcServices</serviceName>
        <dataFormat>netCDF</dataFormat>
        <documentation type="summary">Example BOM</documentation>
      </metadata>

      <collection spec="/system/data/forecast_#yyMMddHHmm#.*\.nc$"/>
      <update startup="test" rescan="0 0/10 * * * ? *" trigger="allow"/>
      <fmrcConfig regularize="false" datasetTypes="Best"/>
    </featureCollection>
  </dataset>