apt_dht/CacheManager.py

   1
   2 from bz2 import BZ2Decompressor
   3 from zlib import decompressobj, MAX_WBITS
   4 from gzip import FCOMMENT, FEXTRA, FHCRC, FNAME, FTEXT
   5 from urlparse import urlparse
   6 import os
   7
   8 from twisted.python import log
   9 from twisted.python.filepath import FilePath
  10 from twisted.internet import defer, reactor
  11 from twisted.trial import unittest
  12 from twisted.web2 import stream
  13 from twisted.web2.http import splitHostPort
  14
  15 from Hash import HashObject
  16
  17 aptpkg_dir='apt-packages'
  18
  19 DECOMPRESS_EXTS = ['.gz', '.bz2']
  20 DECOMPRESS_FILES = ['release', 'sources', 'packages']
  21
  22 class ProxyFileStream(stream.SimpleStream):
  23     """Saves a stream to a file while providing a new stream."""
  24
  25     def __init__(self, stream, outFile, hash, decompress = None, decFile = None):
  26         """Initializes the proxy.
  27
  28         @type stream: C{twisted.web2.stream.IByteStream}
  29         @param stream: the input stream to read from
  30         @type outFile: C{twisted.python.FilePath}
  31         @param outFile: the file to write to
  32         @type hash: L{Hash.HashObject}
  33         @param hash: the hash object to use for the file
  34         @type decompress: C{string}
  35         @param decompress: also decompress the file as this type
  36             (currently only '.gz' and '.bz2' are supported)
  37         @type decFile: C{twisted.python.FilePath}
  38         @param decFile: the file to write the decompressed data to
  39         """
  40         self.stream = stream
  41         self.outFile = outFile.open('w')
  42         self.hash = hash
  43         self.hash.new()
  44         self.gzfile = None
  45         self.bz2file = None
  46         if decompress == ".gz":
  47             self.gzheader = True
  48             self.gzfile = decFile.open('w')
  49             self.gzdec = decompressobj(-MAX_WBITS)
  50         elif decompress == ".bz2":
  51             self.bz2file = decFile.open('w')
  52             self.bz2dec = BZ2Decompressor()
  53         self.length = self.stream.length
  54         self.start = 0
  55         self.doneDefer = defer.Deferred()
  56
  57     def _done(self):
  58         """Close the output file."""
  59         if not self.outFile.closed:
  60             self.outFile.close()
  61             self.hash.digest()
  62             if self.gzfile:
  63                 data_dec = self.gzdec.flush()
  64                 self.gzfile.write(data_dec)
  65                 self.gzfile.close()
  66                 self.gzfile = None
  67             if self.bz2file:
  68                 self.bz2file.close()
  69                 self.bz2file = None
  70
  71             self.doneDefer.callback(self.hash)
  72
  73     def read(self):
  74         """Read some data from the stream."""
  75         if self.outFile.closed:
  76             return None
  77
  78         data = self.stream.read()
  79         if isinstance(data, defer.Deferred):
  80             data.addCallbacks(self._write, self._done)
  81             return data
  82
  83         self._write(data)
  84         return data
  85
  86     def _write(self, data):
  87         """Write the stream data to the file and return it for others to use."""
  88         if data is None:
  89             self._done()
  90             return data
  91
  92         self.outFile.write(data)
  93         self.hash.update(data)
  94         if self.gzfile:
  95             if self.gzheader:
  96                 self.gzheader = False
  97                 new_data = self._remove_gzip_header(data)
  98                 dec_data = self.gzdec.decompress(new_data)
  99             else:
 100                 dec_data = self.gzdec.decompress(data)
 101             self.gzfile.write(dec_data)
 102         if self.bz2file:
 103             dec_data = self.bz2dec.decompress(data)
 104             self.bz2file.write(dec_data)
 105         return data
 106
 107     def _remove_gzip_header(self, data):
 108         if data[:2] != '\037\213':
 109             raise IOError, 'Not a gzipped file'
 110         if ord(data[2]) != 8:
 111             raise IOError, 'Unknown compression method'
 112         flag = ord(data[3])
 113         # modtime = self.fileobj.read(4)
 114         # extraflag = self.fileobj.read(1)
 115         # os = self.fileobj.read(1)
 116
 117         skip = 10
 118         if flag & FEXTRA:
 119             # Read & discard the extra field, if present
 120             xlen = ord(data[10])
 121             xlen = xlen + 256*ord(data[11])
 122             skip = skip + 2 + xlen
 123         if flag & FNAME:
 124             # Read and discard a null-terminated string containing the filename
 125             while True:
 126                 if not data[skip] or data[skip] == '\000':
 127                     break
 128                 skip += 1
 129             skip += 1
 130         if flag & FCOMMENT:
 131             # Read and discard a null-terminated string containing a comment
 132             while True:
 133                 if not data[skip] or data[skip] == '\000':
 134                     break
 135                 skip += 1
 136             skip += 1
 137         if flag & FHCRC:
 138             skip += 2     # Read & discard the 16-bit header CRC
 139         return data[skip:]
 140
 141     def close(self):
 142         """Clean everything up and return None to future reads."""
 143         self.length = 0
 144         self._done()
 145         self.stream.close()
 146
 147 class CacheManager:
 148     """Manages all requests for cached objects."""
 149
 150     def __init__(self, cache_dir, db, other_dirs = [], manager = None):
 151         self.cache_dir = cache_dir
 152         self.other_dirs = other_dirs
 153         self.all_dirs = self.other_dirs[:]
 154         self.all_dirs.insert(0, self.cache_dir)
 155         self.db = db
 156         self.manager = manager
 157         self.scanning = []
 158
 159         # Init the database, remove old files
 160         self.db.removeUntrackedFiles(self.all_dirs)
 161
 162
 163     def scanDirectories(self):
 164         """Scan the cache directories, hashing new and rehashing changed files."""
 165         assert not self.scanning, "a directory scan is already under way"
 166         self.scanning = self.all_dirs[:]
 167         self._scanDirectories()
 168
 169     def _scanDirectories(self, result = None, walker = None):
 170         # Need to start waling a new directory
 171         if walker is None:
 172             # If there are any left, get them
 173             if self.scanning:
 174                 log.msg('started scanning directory: %s' % self.scanning[0].path)
 175                 walker = self.scanning[0].walk()
 176             else:
 177                 log.msg('cache directory scan complete')
 178                 return
 179
 180         try:
 181             # Get the next file in the directory
 182             file = walker.next()
 183         except StopIteration:
 184             # No files left, go to the next directory
 185             log.msg('done scanning directory: %s' % self.scanning[0].path)
 186             self.scanning.pop(0)
 187             reactor.callLater(0, self._scanDirectories)
 188             return
 189
 190         # If it's not a file, or it's already properly in the DB, ignore it
 191         if not file.isfile() or self.db.isUnchanged(file):
 192             if not file.isfile():
 193                 log.msg('entering directory: %s' % file.path)
 194             else:
 195                 log.msg('file is unchanged: %s' % file.path)
 196             reactor.callLater(0, self._scanDirectories, None, walker)
 197             return
 198
 199         # Otherwise hash it
 200         log.msg('start hash checking file: %s' % file.path)
 201         hash = HashObject()
 202         df = hash.hashInThread(file)
 203         df.addBoth(self._doneHashing, file, walker)
 204         df.addErrback(log.err)
 205
 206     def _doneHashing(self, result, file, walker):
 207
 208         if isinstance(result, HashObject):
 209             log.msg('hash check of %s completed with hash: %s' % (file.path, result.hexdigest()))
 210             url = None
 211             if self.scanning[0] == self.cache_dir:
 212                 url = 'http:/' + file.path[len(self.cache_dir.path):]
 213             self.db.storeFile(file, result.digest())
 214             df = self.manager.new_cached_file(file, result, url, True)
 215             if df is None:
 216                 reactor.callLater(0, self._scanDirectories, None, walker)
 217             else:
 218                 df.addBoth(self._scanDirectories, walker)
 219         else:
 220             log.msg('hash check of %s failed' % file.path)
 221             log.err(result)
 222             reactor.callLater(0, self._scanDirectories, None, walker)
 223
 224     def save_file(self, response, hash, url):
 225         """Save a downloaded file to the cache and stream it."""
 226         if response.code != 200:
 227             log.msg('File was not found (%r): %s' % (response, url))
 228             return response
 229
 230         log.msg('Returning file: %s' % url)
 231
 232         parsed = urlparse(url)
 233         destFile = self.cache_dir.preauthChild(parsed[1] + parsed[2])
 234         log.msg('Saving returned %r byte file to cache: %s' % (response.stream.length, destFile.path))
 235
 236         if destFile.exists():
 237             log.msg('File already exists, removing: %s' % destFile.path)
 238             destFile.remove()
 239         elif not destFile.parent().exists():
 240             destFile.parent().makedirs()
 241
 242         root, ext = os.path.splitext(destFile.basename())
 243         if root.lower() in DECOMPRESS_FILES and ext.lower() in DECOMPRESS_EXTS:
 244             ext = ext.lower()
 245             decFile = destFile.sibling(root)
 246             log.msg('Decompressing to: %s' % decFile.path)
 247             if decFile.exists():
 248                 log.msg('File already exists, removing: %s' % decFile.path)
 249                 decFile.remove()
 250         else:
 251             ext = None
 252             decFile = None
 253
 254         orig_stream = response.stream
 255         response.stream = ProxyFileStream(orig_stream, destFile, hash, ext, decFile)
 256         response.stream.doneDefer.addCallback(self._save_complete, url, destFile,
 257                                               response.headers.getHeader('Last-Modified'),
 258                                               ext, decFile)
 259         response.stream.doneDefer.addErrback(self.save_error, url)
 260         return response
 261
 262     def _save_complete(self, hash, url, destFile, modtime = None, ext = None, decFile = None):
 263         """Update the modification time and AptPackages."""
 264         if modtime:
 265             os.utime(destFile.path, (modtime, modtime))
 266             if ext:
 267                 os.utime(decFile.path, (modtime, modtime))
 268
 269         result = hash.verify()
 270         if result or result is None:
 271             if result:
 272                 log.msg('Hashes match: %s' % url)
 273             else:
 274                 log.msg('Hashed file to %s: %s' % (hash.hexdigest(), url))
 275
 276             self.db.storeFile(destFile, hash.digest())
 277             log.msg('now avaliable: %s' % (url))
 278
 279             if self.manager:
 280                 self.manager.new_cached_file(destFile, hash, url)
 281                 if ext:
 282                     self.manager.new_cached_file(decFile, None, url[:-len(ext)])
 283         else:
 284             log.msg("Hashes don't match %s != %s: %s" % (hash.hexexpected(), hash.hexdigest(), url))
 285             destFile.remove()
 286             if ext:
 287                 decFile.remove()
 288
 289     def save_error(self, failure, url):
 290         """An error has occurred in downloadign or saving the file."""
 291         log.msg('Error occurred downloading %s' % url)
 292         log.err(failure)
 293         return failure
 294
 295 class TestMirrorManager(unittest.TestCase):
 296     """Unit tests for the mirror manager."""
 297
 298     timeout = 20
 299     pending_calls = []
 300     client = None
 301
 302     def setUp(self):
 303         self.client = CacheManager(FilePath('/tmp/.apt-dht'))
 304
 305     def tearDown(self):
 306         for p in self.pending_calls:
 307             if p.active():
 308                 p.cancel()
 309         self.client = None
 310