Integrating New Zarr Data Stores¶
ZarrIO
by default uses the Zarr
DirectoryStore via
the zarr.convenience.open()
method. ZarrIO
further
supports all stores listed in SUPPORTED_ZARR_STORES
.
Users can specify a particular store using the path
parameter when creating a new
ZarrIO
instance. This document discusses key steps towards
integrating other data stores available for Zarr with ZarrIO
.
Updating ZarrIO¶
Import and add the new storage class to the
SUPPORTED_ZARR_STORES
. This will in turn allow instances of your new storage class to be passed as apath
parameter to__init__()
andload_namespaces()
and passdocval()
validation for these functions.Depending on the type of data store, it may also be necessary to update the handling of links and references in
ZarrIO
. In principle, reading and writing of links should not need to change, however, in particular the__resolve_ref()
andget_builder_exists_on_disk()
method may need to be updated to ensure references are opened correctly on read for files stored with your new store. The__get_ref()
function may also need to be updated, in particular in case the links to your store also modify the storage schema for links (e.g., if you need to store additional metadata in order to resolve links to your store).
Updating NWBZarrIO¶
In most cases we should not need to update NWBZarrIO
as it inherits
directly from ZarrIO
. However, in particular if the interface for
__init__
has changed for ZarrIO
,
then we may also need to modify NWBZarrIO
accordingly.
Updating Unit Tests¶
Much of the core test harness of hdmf_zarr
is modularized to simplify running existing
tests with new storage backends. In this way, we can quickly create a collection of common tests
for new backends, and new test cases added to the test suite can be run with all backends.
The relevant test class are located in the /tests/unit
directory of the hdmf_zarr repository.
test_zarrio.py¶
base_tests_zarrio.py
provides a collection of base classes that define common
test cases to test basic functionality of ZarrIO
. Using these base classes, the
test_zarrio.py module
then implements concrete tests for various backends. To create tests for a new data store, we need to
add the following main classes (while <MyStore>
in the code below would need to be replaced with the
class name of the new data store):
Create tests for new data store: Add the following main classes (while
<MyStore>
in the code below would need to be replaces with the class name of the new data store):######################################### # <MyStore> tests ######################################### class TestZarrWriter<MyStore>(BaseTestZarrWriter): """Test writing of builder with Zarr using a custom <MyStore>""" def setUp(self): super().setUp() self.store = <MyStore>() self.store_path = self.store.path class TestZarrWriteUnit<MyStore>(BaseTestZarrWriteUnit): """Unit test for individual write functions using a custom <MyStore>""" def setUp(self): super().setUp() self.store = <MyStore>() self.store_path = self.store.path class TestExportZarrToZarr<MyStore>(BaseTestExportZarrToZarr): """Test exporting Zarr to Zarr using <MyStore>.""" def setUp(self): super().setUp() self.stores = [<MyStore>() for i in range(len(self.store_path))] self.store_paths = [s.path for s in self.stores]
Update ``base_tests_zarrio.reopen_store`` If our new data store cannot be reused after it has been closed via
close()
, then update the method to either reopen or create a new equivalent data store that can be used for read. The function is used in tests that write data, then close the ZarrIO, and create a new ZarrIO to read and validate the data.Run and update tests Depending on your data store, some test cases in
BaseTestZarrWriter
,BaseTestZarrWriteUnit
orBaseTestExportZarrToZarr
may need to be updated to correctly work with our data store. Simply run the test suite to see if any cases are failing to see whether thesetUp
in your test classes or any specific test cases may need to be updated.
test_io_convert.py¶
test_io_convert.py uses a collection of mixin classes to define custom test classes to test export from one IO backend to another. As such, the test cases here typically first write to one target and then export to another target and then compare that the data between the two files is consistent.
Update ``MixinTestHDF5ToZarr``, ``MixinTestZarrToZarr``, and ``MixinTestZarrToZarr`` mixin classes to add the new backend to the
WRITE_PATHS
(if Zarr is the initial write target) and/orEXPORT_PATHS
(if Zarr is the export target) variables to define our store as a write or export store forZarrIO
, respectively. Once we have added our new store as write/export targets to these mixins, all test cases defined in the module will be run with our new backend. Specifically, we here commonly need to add an instance of our new data store to:MixinTestHDF5ToZarr.EXPORT_PATHS
MixinTestZarrToHDF5.WRITE_PATHS
MixinTestZarrToZarr.WRITE_PATHS
andMixinTestZarrToZarr.EXPORT_PATHS
Update tests and ZarrIO as necessary Run the test suite and fix any identified issues.