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 ignore it
 191         if not file.isfile():
 192             log.msg('entering directory: %s' % file.path)
 193             reactor.callLater(0, self._scanDirectories, None, walker)
 194             return
 195
 196         # If it's already properly in the DB, ignore it
 197         if self.db.isUnchanged(file):
 198             log.msg('file is unchanged: %s' % file.path)
 199             reactor.callLater(0, self._scanDirectories, None, walker)
 200             return
 201
 202         # Don't hash files in the cache that are not in the DB
 203         if self.scanning[0] == self.cache_dir:
 204             log.msg('ignoring unknown cache file: %s' % file.path)
 205             reactor.callLater(0, self._scanDirectories, None, walker)
 206             return
 207
 208         # Otherwise hash it
 209         log.msg('start hash checking file: %s' % file.path)
 210         hash = HashObject()
 211         df = hash.hashInThread(file)
 212         df.addBoth(self._doneHashing, file, walker)
 213         df.addErrback(log.err)
 214
 215     def _doneHashing(self, result, file, walker):
 216
 217         if isinstance(result, HashObject):
 218             log.msg('hash check of %s completed with hash: %s' % (file.path, result.hexdigest()))
 219             url = None
 220             if self.scanning[0] == self.cache_dir:
 221                 url = 'http:/' + file.path[len(self.cache_dir.path):]
 222             new_hash = self.db.storeFile(file, result.digest())
 223             df = self.manager.new_cached_file(file, result, new_hash, url, True)
 224             if df is None:
 225                 reactor.callLater(0, self._scanDirectories, None, walker)
 226             else:
 227                 df.addBoth(self._scanDirectories, walker)
 228         else:
 229             log.msg('hash check of %s failed' % file.path)
 230             log.err(result)
 231             reactor.callLater(0, self._scanDirectories, None, walker)
 232
 233     def save_file(self, response, hash, url):
 234         """Save a downloaded file to the cache and stream it."""
 235         if response.code != 200:
 236             log.msg('File was not found (%r): %s' % (response, url))
 237             return response
 238
 239         log.msg('Returning file: %s' % url)
 240
 241         parsed = urlparse(url)
 242         destFile = self.cache_dir.preauthChild(parsed[1] + parsed[2])
 243         log.msg('Saving returned %r byte file to cache: %s' % (response.stream.length, destFile.path))
 244
 245         if destFile.exists():
 246             log.msg('File already exists, removing: %s' % destFile.path)
 247             destFile.remove()
 248         elif not destFile.parent().exists():
 249             destFile.parent().makedirs()
 250
 251         root, ext = os.path.splitext(destFile.basename())
 252         if root.lower() in DECOMPRESS_FILES and ext.lower() in DECOMPRESS_EXTS:
 253             ext = ext.lower()
 254             decFile = destFile.sibling(root)
 255             log.msg('Decompressing to: %s' % decFile.path)
 256             if decFile.exists():
 257                 log.msg('File already exists, removing: %s' % decFile.path)
 258                 decFile.remove()
 259         else:
 260             ext = None
 261             decFile = None
 262
 263         orig_stream = response.stream
 264         response.stream = ProxyFileStream(orig_stream, destFile, hash, ext, decFile)
 265         response.stream.doneDefer.addCallback(self._save_complete, url, destFile,
 266                                               response.headers.getHeader('Last-Modified'),
 267                                               ext, decFile)
 268         response.stream.doneDefer.addErrback(self.save_error, url)
 269         return response
 270
 271     def _save_complete(self, hash, url, destFile, modtime = None, ext = None, decFile = None):
 272         """Update the modification time and AptPackages."""
 273         if modtime:
 274             os.utime(destFile.path, (modtime, modtime))
 275             if ext:
 276                 os.utime(decFile.path, (modtime, modtime))
 277
 278         result = hash.verify()
 279         if result or result is None:
 280             if result:
 281                 log.msg('Hashes match: %s' % url)
 282             else:
 283                 log.msg('Hashed file to %s: %s' % (hash.hexdigest(), url))
 284
 285             new_hash = self.db.storeFile(destFile, hash.digest())
 286             log.msg('now avaliable: %s' % (url))
 287
 288             if self.manager:
 289                 self.manager.new_cached_file(destFile, hash, new_hash, url)
 290                 if ext:
 291                     self.manager.new_cached_file(decFile, None, False, url[:-len(ext)])
 292         else:
 293             log.msg("Hashes don't match %s != %s: %s" % (hash.hexexpected(), hash.hexdigest(), url))
 294             destFile.remove()
 295             if ext:
 296                 decFile.remove()
 297
 298     def save_error(self, failure, url):
 299         """An error has occurred in downloadign or saving the file."""
 300         log.msg('Error occurred downloading %s' % url)
 301         log.err(failure)
 302         return failure
 303
 304 class TestMirrorManager(unittest.TestCase):
 305     """Unit tests for the mirror manager."""
 306
 307     timeout = 20
 308     pending_calls = []
 309     client = None
 310
 311     def setUp(self):
 312         self.client = CacheManager(FilePath('/tmp/.apt-dht'))
 313
 314     def tearDown(self):
 315         for p in self.pending_calls:
 316             if p.active():
 317                 p.cancel()
 318         self.client = None
 319