Add tables_open_file func to retry opening

ska_helpers/retry/__init__.py

@@ -19,12 +19,12 @@
 See the License for the specific language governing permissions and
 limitations under the License.
 """
-__all__ = ['retry', 'retry_call', 'RetryError']
+__all__ = ['retry', 'retry_call', 'RetryError', 'tables_open_file']
 
 import logging
 from logging import StreamHandler
 
-from .api import retry, retry_call, RetryError
+from .api import retry, retry_call, RetryError, tables_open_file
 
 log = logging.getLogger(__name__)
 log.addHandler(StreamHandler())

ska_helpers/retry/api.py

@@ -8,6 +8,7 @@
 
 logging_logger = logging.getLogger(__name__)
 
+
 class RetryError(Exception):
     """
     Keep track of the stack of exceptions when trying multiple times.
@@ -131,3 +132,24 @@ def retry_call(f, args=None, kwargs=None, exceptions=Exception, tries=-1, delay=
 
     return __retry_internal(f, exceptions, tries, delay, max_delay,
                             backoff, jitter, logger, args=args, kwargs=kwargs)
+
+
+def tables_open_file(*args, **kwargs):
+    """Call tables.open_file(*args, **kwargs) with retry up to 3 times.
+
+    This only catches tables.exceptions.HDF5ExtError. After an initial failure
+    it will try again after 2 seconds and once more after 4 seconds.
+
+    :param *args: args passed through to tables.open_file()
+    :param **kwargs: kwargs passed through to tables.open_file()
+    :returns: tables file handle
+    """
+    import ska_helpers.retry
+    import tables
+    import tables.exceptions
+
+    h5 = ska_helpers.retry.retry_call(
+        tables.open_file, args=args, kwargs=kwargs,
+        exceptions=tables.exceptions.HDF5ExtError,
+        delay=2, tries=3, backoff=2)
+    return h5

ska_helpers/utils.py

@@ -192,5 +192,3 @@ def cache_info():
         _wrapped.cache_clear = func.cache_clear
         return _wrapped
     return _wrapper
-
-