[thredds] TDS and netCDF-4 Writing

• To: thredds@xxxxxxxxxxxxxxxx
• Subject: [thredds] TDS and netCDF-4 Writing
• From: Sean Arms <sarms@xxxxxxxxxxxxxxxx>
• Date: Tue, 20 Aug 2013 11:37:45 -0600

Greetings!

We have found an issue with netCDF-4 writing in the the TDS. This
basically stems from netCDF and HDF5 not being thread-safe by default,
and the end result is a nice, shiny core dump. Currently, the netCDF-C
library is not thread-safe, but the HDF5 library can be configured to
ensure a basic level of thread safety. If you have enabled netCDF-4
output from the TDS, we *strongly* encourage you to use a thread-safe
version of HDF5! Please see the netCDF-Java documentation:

http://www.unidata.ucar.edu/software/netcdf-java/reference/netcdf4Clibrary.html

or the HDF5 FAQ

http://www.hdfgroup.org/hdf5-quest.html#mthread

for information on how to build a thread-safe HDF5 library.

Please note that while building HDF5 as a thread-safe library will solve
the core dump issue (well, at least the one we've found), there still
may be issues since netCDF-4 is not thread-safe. The netCDF-C group is
looking into ways to make the netCDF-C library thread-safe, but in the
meantime, if you find any bugs, please let us know.

Cheers!

Sean