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# Copyright (C) 2010 Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import math
import logging
from google.appengine.ext import blobstore
from google.appengine.ext import db
MAX_DATA_ENTRY_PER_FILE = 30
MAX_ENTRY_LEN = 1000 * 1000
class ChunkData:
def __init__(self):
self.reused_key = None
self.data_entry = None
self.entry_future = None
self.index = None
class DataEntry(db.Model):
"""Datastore entry that stores one segmant of file data
(<1000*1000 bytes).
"""
data = db.BlobProperty()
@classmethod
def get(cls, key):
return db.get(key)
@classmethod
def get_async(cls, key):
return db.get_async(key)
@classmethod
def delete_async(cls, key):
return db.delete_async(key)
class DataStoreFile(db.Model):
"""This class stores file in datastore.
If a file is oversize (>1000*1000 bytes), the file is split into
multiple segments and stored in multiple datastore entries.
"""
name = db.StringProperty()
data_keys = db.ListProperty(db.Key)
# keys to the data store entries that can be reused for new data.
# If it is emtpy, create new DataEntry.
new_data_keys = db.ListProperty(db.Key)
date = db.DateTimeProperty(auto_now_add=True)
data = None
def _get_chunk_indices(self, data_length):
nchunks = math.ceil(float(data_length) / MAX_ENTRY_LEN)
return xrange(0, int(nchunks) * MAX_ENTRY_LEN, MAX_ENTRY_LEN)
def _convert_blob_keys(self, keys):
converted_keys = []
for key in keys:
new_key = blobstore.BlobMigrationRecord.get_new_blob_key(key)
if new_key:
converted_keys.append(new_key)
else:
converted_keys.append(key)
return keys
def delete_data(self, keys=None):
if not keys:
keys = self._convert_blob_keys(self.data_keys)
logging.info('Doing async delete of keys: %s', keys)
get_futures = [DataEntry.get_async(k) for k in keys]
delete_futures = []
for get_future in get_futures:
result = get_future.get_result()
if result:
delete_futures.append(DataEntry.delete_async(result.key()))
for delete_future in delete_futures:
delete_future.get_result()
def save_data(self, data):
if not data:
logging.warning("No data to save.")
return False
if len(data) > (MAX_DATA_ENTRY_PER_FILE * MAX_ENTRY_LEN):
logging.error("File too big, can't save to datastore: %dK",
len(data) / 1024)
return False
start = 0
# Use the new_data_keys to store new data. If all new data are saved
# successfully, swap new_data_keys and data_keys so we can reuse the
# data_keys entries in next run. If unable to save new data for any
# reason, only the data pointed by new_data_keys may be corrupted,
# the existing data_keys data remains untouched. The corrupted data
# in new_data_keys will be overwritten in next update.
keys = self._convert_blob_keys(self.new_data_keys)
self.new_data_keys = []
chunk_indices = self._get_chunk_indices(len(data))
logging.info('Saving file in %s chunks', len(chunk_indices))
chunk_data = []
for chunk_index in chunk_indices:
chunk = ChunkData()
chunk.index = chunk_index
if keys:
chunk.reused_key = keys.pop()
chunk.entry_future = DataEntry.get_async(chunk.reused_key)
else:
chunk.data_entry = DataEntry()
chunk_data.append(chunk)
put_futures = []
for chunk in chunk_data:
if chunk.entry_future:
data_entry = chunk.entry_future.get_result()
if not data_entry:
logging.warning("Found key, but no data entry: %s", chunk.reused_key)
data_entry = DataEntry()
chunk.data_entry = data_entry
chunk.data_entry.data = db.Blob(data[chunk.index: chunk.index + MAX_ENTRY_LEN])
put_futures.append(db.put_async(chunk.data_entry))
for future in put_futures:
key = None
try:
key = future.get_result()
self.new_data_keys.append(key)
except Exception, err:
logging.error("Failed to save data store entry: %s", err)
self.delete_data(keys)
return False
if keys:
self.delete_data(keys)
temp_keys = self._convert_blob_keys(self.data_keys)
self.data_keys = self.new_data_keys
self.new_data_keys = temp_keys
self.data = data
return True
def load_data(self):
if not self.data_keys:
logging.warning("No data to load.")
return None
data_futures = [(k, DataEntry.get_async(k)) for k in self._convert_blob_keys(self.data_keys)]
data = []
for key, future in data_futures:
result = future.get_result()
if not result:
logging.error("No data found for key: %s.", key)
return None
data.append(result)
self.data = "".join([d.data for d in data])
return self.data
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