[netcdf-java] zarr

• To: Java NetCDF <netcdf-java@xxxxxxxxxxxxxxxx>
• Subject: [netcdf-java] zarr
• From: Bob Simons - NOAA Federal <bob.simons@xxxxxxxx>
• Date: Thu, 11 Aug 2022 14:28:14 -0400

The netcdf-java documentation says that it now supports reading data from
zarr "files".
https://docs.unidata.ucar.edu/netcdf-java/5.5/userguide/reading_zarr.html
I'm trying to experiment with that (in netcdf-java 5.5.3) and not having
any luck.

One option listed there is
  NetcdfFile objectStoreZarr = NetcdfFiles.open(pathToObjectStore);
I found a sample zarr file on the web at
https://hrrrzarr.s3.amazonaws.com/index.html#sfc/20160823/
If I try
  NetcdfFile objectStoreZarr = NetcdfFiles.open("
https://hrrrzarr.s3.amazonaws.com/sfc/20160823/20160823_14z_anl.zarr";);
or other variants, it fails with
Exception in thread "main" java.io.FileNotFoundException:
https://hrrrzarr.s3.amazonaws.com/sfc/20160823/20160823_14z_anl.zarr
HTTP/1.1 404 Not Found
        at
ucar.unidata.io.http.HTTPRandomAccessFile.doConnect(HTTPRandomAccessFile.java:137)
        at
ucar.unidata.io.http.HTTPRandomAccessFile.<init>(HTTPRandomAccessFile.java:69)
        at
ucar.unidata.io.http.HTTPRandomAccessFile$Provider.open(HTTPRandomAccessFile.java:256)
        at ucar.nc2.NetcdfFiles.getRaf(NetcdfFiles.java:411)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:274)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:243)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:216)
I tried other variants (with/without the trailing '/', the parent
directory, etc), but all without success.

I also copied all of the 20160803 directory to my local computer with AWS
CLI, then tried to open the local zarr file with
NetcdfFile directoryStoreZarr = NetcdfFiles.open(pathToDirectoryStore);
i.e.,
NetcdfFiles.open("c:/erddapTest/zarr/20160803/20160803_14z_anl.zarr/");
That fails with
Exception in thread "main" java.io.FileNotFoundException:
c:\erddapTest\zarr\20160803\20160803_14z_anl.zarr (The system cannot find
the path specified)
        at java.base/java.io.RandomAccessFile.open0(Native Method)
        at
java.base/java.io.RandomAccessFile.open(RandomAccessFile.java:344)
        at
java.base/java.io.RandomAccessFile.<init>(RandomAccessFile.java:259)
        at
java.base/java.io.RandomAccessFile.<init>(RandomAccessFile.java:213)
        at
java.base/java.io.RandomAccessFile.<init>(RandomAccessFile.java:127)
        at
ucar.unidata.io.RandomAccessFile.<init>(RandomAccessFile.java:322)
        at
ucar.unidata.io.RandomAccessFile.acquire(RandomAccessFile.java:192)
        at ucar.nc2.NetcdfFiles.getRaf(NetcdfFiles.java:465)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:274)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:243)
        at ucar.nc2.NetcdfFiles.open(NetcdfFiles.java:216)
I tried a lot of variants of the "file" name, and just got the same error.

Can you please tell me what I'm doing wrong?
Or, can you send me a simple example that works?

If you also have a simple example with a .zip file that I can download,
that would be great.

Thank you.