1# Copyright (C) 2010 Google Inc. All rights reserved. 2# 3# Redistribution and use in source and binary forms, with or without 4# modification, are permitted provided that the following conditions are 5# met: 6# 7# * Redistributions of source code must retain the above copyright 8# notice, this list of conditions and the following disclaimer. 9# * Redistributions in binary form must reproduce the above 10# copyright notice, this list of conditions and the following disclaimer 11# in the documentation and/or other materials provided with the 12# distribution. 13# * Neither the name of Google Inc. nor the names of its 14# contributors may be used to endorse or promote products derived from 15# this software without specific prior written permission. 16# 17# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 29import math 30import logging 31 32from google.appengine.ext import blobstore 33from google.appengine.ext import db 34 35MAX_DATA_ENTRY_PER_FILE = 30 36MAX_ENTRY_LEN = 1000 * 1000 37 38 39class ChunkData: 40 def __init__(self): 41 self.reused_key = None 42 self.data_entry = None 43 self.entry_future = None 44 self.index = None 45 46 47class DataEntry(db.Model): 48 """Datastore entry that stores one segmant of file data 49 (<1000*1000 bytes). 50 """ 51 52 data = db.BlobProperty() 53 54 @classmethod 55 def get(cls, key): 56 return db.get(key) 57 58 @classmethod 59 def get_async(cls, key): 60 return db.get_async(key) 61 62 @classmethod 63 def delete_async(cls, key): 64 return db.delete_async(key) 65 66 67class DataStoreFile(db.Model): 68 """This class stores file in datastore. 69 If a file is oversize (>1000*1000 bytes), the file is split into 70 multiple segments and stored in multiple datastore entries. 71 """ 72 73 name = db.StringProperty() 74 data_keys = db.ListProperty(db.Key) 75 # keys to the data store entries that can be reused for new data. 76 # If it is emtpy, create new DataEntry. 77 new_data_keys = db.ListProperty(db.Key) 78 date = db.DateTimeProperty(auto_now_add=True) 79 80 data = None 81 82 def _get_chunk_indices(self, data_length): 83 nchunks = math.ceil(float(data_length) / MAX_ENTRY_LEN) 84 return xrange(0, int(nchunks) * MAX_ENTRY_LEN, MAX_ENTRY_LEN) 85 86 def _convert_blob_keys(self, keys): 87 converted_keys = [] 88 for key in keys: 89 new_key = blobstore.BlobMigrationRecord.get_new_blob_key(key) 90 if new_key: 91 converted_keys.append(new_key) 92 else: 93 converted_keys.append(key) 94 return keys 95 96 def delete_data(self, keys=None): 97 if not keys: 98 keys = self._convert_blob_keys(self.data_keys) 99 logging.info('Doing async delete of keys: %s', keys) 100 101 get_futures = [DataEntry.get_async(k) for k in keys] 102 delete_futures = [] 103 for get_future in get_futures: 104 result = get_future.get_result() 105 if result: 106 delete_futures.append(DataEntry.delete_async(result.key())) 107 108 for delete_future in delete_futures: 109 delete_future.get_result() 110 111 def save_data(self, data): 112 if not data: 113 logging.warning("No data to save.") 114 return False 115 116 if len(data) > (MAX_DATA_ENTRY_PER_FILE * MAX_ENTRY_LEN): 117 logging.error("File too big, can't save to datastore: %dK", 118 len(data) / 1024) 119 return False 120 121 start = 0 122 # Use the new_data_keys to store new data. If all new data are saved 123 # successfully, swap new_data_keys and data_keys so we can reuse the 124 # data_keys entries in next run. If unable to save new data for any 125 # reason, only the data pointed by new_data_keys may be corrupted, 126 # the existing data_keys data remains untouched. The corrupted data 127 # in new_data_keys will be overwritten in next update. 128 keys = self._convert_blob_keys(self.new_data_keys) 129 self.new_data_keys = [] 130 131 chunk_indices = self._get_chunk_indices(len(data)) 132 logging.info('Saving file in %s chunks', len(chunk_indices)) 133 134 chunk_data = [] 135 for chunk_index in chunk_indices: 136 chunk = ChunkData() 137 chunk.index = chunk_index 138 if keys: 139 chunk.reused_key = keys.pop() 140 chunk.entry_future = DataEntry.get_async(chunk.reused_key) 141 else: 142 chunk.data_entry = DataEntry() 143 chunk_data.append(chunk) 144 145 put_futures = [] 146 for chunk in chunk_data: 147 if chunk.entry_future: 148 data_entry = chunk.entry_future.get_result() 149 if not data_entry: 150 logging.warning("Found key, but no data entry: %s", chunk.reused_key) 151 data_entry = DataEntry() 152 chunk.data_entry = data_entry 153 154 chunk.data_entry.data = db.Blob(data[chunk.index: chunk.index + MAX_ENTRY_LEN]) 155 put_futures.append(db.put_async(chunk.data_entry)) 156 157 for future in put_futures: 158 key = None 159 try: 160 key = future.get_result() 161 self.new_data_keys.append(key) 162 except Exception, err: 163 logging.error("Failed to save data store entry: %s", err) 164 self.delete_data(keys) 165 return False 166 167 if keys: 168 self.delete_data(keys) 169 170 temp_keys = self._convert_blob_keys(self.data_keys) 171 self.data_keys = self.new_data_keys 172 self.new_data_keys = temp_keys 173 self.data = data 174 175 return True 176 177 def load_data(self): 178 if not self.data_keys: 179 logging.warning("No data to load.") 180 return None 181 182 data_futures = [(k, DataEntry.get_async(k)) for k in self._convert_blob_keys(self.data_keys)] 183 184 data = [] 185 for key, future in data_futures: 186 result = future.get_result() 187 if not result: 188 logging.error("No data found for key: %s.", key) 189 return None 190 data.append(result) 191 192 self.data = "".join([d.data for d in data]) 193 194 return self.data 195