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# -------------------------------------------------------------------------
# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License. See License.txt in the project root for
# license information.
# --------------------------------------------------------------------------
import threading
def _download_blob_chunks(blob_service, container_name, blob_name, snapshot,
download_size, block_size, progress, start_range, end_range,
stream, max_connections, progress_callback, validate_content,
lease_id, if_modified_since, if_unmodified_since, if_match,
if_none_match, timeout, operation_context):
downloader_class = _ParallelBlobChunkDownloader if max_connections > 1 else _SequentialBlobChunkDownloader
downloader = downloader_class(
blob_service,
container_name,
blob_name,
snapshot,
download_size,
block_size,
progress,
start_range,
end_range,
stream,
progress_callback,
validate_content,
lease_id,
if_modified_since,
if_unmodified_since,
if_match,
if_none_match,
timeout,
operation_context,
)
if max_connections > 1:
import concurrent.futures
executor = concurrent.futures.ThreadPoolExecutor(max_connections)
list(executor.map(downloader.process_chunk, downloader.get_chunk_offsets()))
else:
for chunk in downloader.get_chunk_offsets():
downloader.process_chunk(chunk)
class _BlobChunkDownloader(object):
def __init__(self, blob_service, container_name, blob_name, snapshot, download_size,
chunk_size, progress, start_range, end_range, stream,
progress_callback, validate_content, lease_id, if_modified_since,
if_unmodified_since, if_match, if_none_match, timeout, operation_context):
# identifiers for the blob
self.blob_service = blob_service
self.container_name = container_name
self.blob_name = blob_name
self.snapshot = snapshot
# information on the download range/chunk size
self.chunk_size = chunk_size
self.download_size = download_size
self.start_index = start_range
self.blob_end = end_range
# the destination that we will write to
self.stream = stream
# progress related
self.progress_callback = progress_callback
self.progress_total = progress
# parameters for each get blob operation
self.timeout = timeout
self.operation_context = operation_context
self.validate_content = validate_content
self.lease_id = lease_id
self.if_modified_since = if_modified_since
self.if_unmodified_since = if_unmodified_since
self.if_match = if_match
self.if_none_match = if_none_match
def get_chunk_offsets(self):
index = self.start_index
while index < self.blob_end:
yield index
index += self.chunk_size
def process_chunk(self, chunk_start):
if chunk_start + self.chunk_size > self.blob_end:
chunk_end = self.blob_end
else:
chunk_end = chunk_start + self.chunk_size
chunk_data = self._download_chunk(chunk_start, chunk_end).content
length = chunk_end - chunk_start
if length > 0:
self._write_to_stream(chunk_data, chunk_start)
self._update_progress(length)
# should be provided by the subclass
def _update_progress(self, length):
pass
# should be provided by the subclass
def _write_to_stream(self, chunk_data, chunk_start):
pass
def _download_chunk(self, chunk_start, chunk_end):
response = self.blob_service._get_blob(
self.container_name,
self.blob_name,
snapshot=self.snapshot,
start_range=chunk_start,
end_range=chunk_end - 1,
validate_content=self.validate_content,
lease_id=self.lease_id,
if_modified_since=self.if_modified_since,
if_unmodified_since=self.if_unmodified_since,
if_match=self.if_match,
if_none_match=self.if_none_match,
timeout=self.timeout,
_context=self.operation_context
)
# This makes sure that if_match is set so that we can validate
# that subsequent downloads are to an unmodified blob
self.if_match = response.properties.etag
return response
class _ParallelBlobChunkDownloader(_BlobChunkDownloader):
def __init__(self, blob_service, container_name, blob_name, snapshot, download_size,
chunk_size, progress, start_range, end_range, stream,
progress_callback, validate_content, lease_id, if_modified_since,
if_unmodified_since, if_match, if_none_match, timeout, operation_context):
super(_ParallelBlobChunkDownloader, self).__init__(blob_service, container_name, blob_name, snapshot,
download_size,
chunk_size, progress, start_range, end_range, stream,
progress_callback, validate_content, lease_id,
if_modified_since,
if_unmodified_since, if_match, if_none_match, timeout,
operation_context)
# for a parallel download, the stream is always seekable, so we note down the current position
# in order to seek to the right place when out-of-order chunks come in
self.stream_start = stream.tell()
# since parallel operations are going on
# it is essential to protect the writing and progress reporting operations
self.stream_lock = threading.Lock()
self.progress_lock = threading.Lock()
def _update_progress(self, length):
if self.progress_callback is not None:
with self.progress_lock:
self.progress_total += length
total_so_far = self.progress_total
self.progress_callback(total_so_far, self.download_size)
def _write_to_stream(self, chunk_data, chunk_start):
with self.stream_lock:
self.stream.seek(self.stream_start + (chunk_start - self.start_index))
self.stream.write(chunk_data)
class _SequentialBlobChunkDownloader(_BlobChunkDownloader):
def __init__(self, *args):
super(_SequentialBlobChunkDownloader, self).__init__(*args)
def _update_progress(self, length):
if self.progress_callback is not None:
self.progress_total += length
self.progress_callback(self.progress_total, self.download_size)
def _write_to_stream(self, chunk_data, chunk_start):
# chunk_start is ignored in the case of sequential download since we cannot seek the destination stream
self.stream.write(chunk_data)
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