[GitHub] szha commented on a change in pull request #9671: Exp backoff for downloads.

[GitBox <gi...@apache.org>]

szha commented on a change in pull request #9671: Exp backoff for downloads.
URL: https://github.com/apache/incubator-mxnet/pull/9671#discussion_r165443664
 
 

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 File path: python/mxnet/utils.py
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 @@ -0,0 +1,151 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""Utility functions applicable to all areas of code (tests, tutorials, gluon, etc)."""
+
+__all__ = ['check_sha1', 'download', 'create_dir']
+
+import errno
+import logging
+import time
+import os
+import hashlib
+
+try:
+    import requests
+except ImportError:
+    class requests_failed_to_import(object):
+        pass
+    requests = requests_failed_to_import
+
+
+def check_sha1(filename, sha1_hash):
+    """Check whether the sha1 hash of the file content matches the expected hash.
+
+    Parameters
+    ----------
+    filename : str
+        Path to the file.
+    sha1_hash : str
+        Expected sha1 hash in hexadecimal digits.
+
+    Returns
+    -------
+    bool
+        Whether the file content matches the expected hash.
+    """
+    sha1 = hashlib.sha1()
+    with open(filename, 'rb') as f:
+        while True:
+            data = f.read(1048576)
+            if not data:
+                break
+            sha1.update(data)
+
+    return sha1.hexdigest() == sha1_hash
+
+
+def _download_retry_with_backoff(fname, url, max_attempts=4):
+    """Downloads a url with backoff applied, automatically re-requesting after a failure.
 
 Review comment:
   Retry can be added to existing download function.

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