Source Code for Module flumotion.component.misc.httpserver.httpcached.resource_manager

  1  # -*- Mode: Python; test-case-name: flumotion.test.test_component_providers -*- 
  2  # vi:si:et:sw=4:sts=4:ts=4 
  3  # 
  4  # Flumotion - a streaming media server 
  5  # Copyright (C) 2004,2005,2006,2007,2008 Fluendo, S.L. (www.fluendo.com). 
  6  # All rights reserved. 
  7   
  8  # This file may be distributed and/or modified under the terms of 
  9  # the GNU General Public License version 2 as published by 
 10  # the Free Software Foundation. 
 11  # This file is distributed without any warranty; without even the implied 
 12  # warranty of merchantability or fitness for a particular purpose. 
 13  # See "LICENSE.GPL" in the source distribution for more information. 
 14   
 15  # Licensees having purchased or holding a valid Flumotion Advanced 
 16  # Streaming Server license may use this file in accordance with the 
 17  # Flumotion Advanced Streaming Server Commercial License Agreement. 
 18  # See "LICENSE.Flumotion" in the source distribution for more information. 
 19   
 20  # Headers in this file shall remain intact. 
 21   
 22  import errno 
 23   
 24  from twisted.internet import defer 
 25   
 26  from flumotion.common import log 
 27   
 28  from flumotion.component.misc.httpserver import fileprovider 
 29  from flumotion.component.misc.httpserver import cachestats 
 30   
 31  LOG_CATEGORY = "resource-manager" 
 32   
 33   
 34  errnoLookup = {errno.ENOENT: fileprovider.NotFoundError, 
 35                 errno.EISDIR: fileprovider.CannotOpenError, 
 36                 errno.EACCES: fileprovider.AccessError} 
 37   
 38   
 39 -class DataSource(object): 
 40      """ 
 41      Base class for all resources data source. 
 42      """ 
 43   
 44      url = None 
 45      identifier = None 
 46      mimeType = None 
 47      mtime = None 
 48      size = None 
 49   
 50 -    def read(self, offset, size): 
 51          raise NotImplementedError() 
 52   
 53 -    def close(self): 
 54          raise NotImplementedError() 
 55   
 56   
 57 -class ResourceManager(log.Loggable): 
 58      """ 
 59      Provide file-like resources for URLs. 
 60      """ 
 61   
 62      logCategory = LOG_CATEGORY 
 63   
 64 -    def __init__(self, strategy, stats): 
 65          self.strategy = strategy 
 66          self.stats = stats 
 67   
 68 -    def getResourceFor(self, url): 
 69          self.debug("Resource requested with %s", url) 
 70   
 71          stats = cachestats.RequestStatistics(self.stats) 
 72   
 73          d = defer.Deferred() 
 74          d.addCallback(self.strategy.getSourceFor, stats) 
 75          d.addCallback(Resource, stats) 
 76   
 77          d.callback(url) 
 78   
 79          return d 
 80   
 81   
 82 -class Resource(object): 
 83      """ 
 84      Offers a file-like interface of a data source. 
 85      Handle errors and asynchronous readings and file offset. 
 86      """ 
 87   
 88 -    def __init__(self, source, stats): 
 89          self._open(source) 
 90          self._offset = 0 
 91          self._reading = False 
 92          self.stats = stats 
 93   
 94 -    def getMimeType(self): 
 95          return self.mimeType 
 96   
 97 -    def getmtime(self): 
 98          return self._source.mtime 
 99   
100 -    def getsize(self): 
101          return self._source.size 
102   
103 -    def tell(self): 
104          return self._offset 
105   
106 -    def seek(self, offset): 
107          self._check() 
108          self._offset = offset 
109   
110 -    def read(self, size): 
111          self._check() 
112          assert not self._reading, "Simultaneous read not supported" 
113          try: 
114              d = self._source.read(self._offset, size) 
115              if isinstance(d, defer.Deferred): 
116                  self._reading = True 
117                  return d.addCallback(self._cbUpdateOffset) 
118              self._offset += len(d) 
119              return defer.succeed(d) 
120          except IOError, e: 
121              cls = errnoLookup.get(e.errno, fileprovider.FileError) 
122              return defer.fail(cls("Failed to read data: %s", str(e))) 
123          except: 
124              return defer.fail() 
125   
126 -    def produce(self, consumer, fromOffset=None): 
127          """ 
128          Returns a producer that produce data from the specified position 
129          or from the current position if None is specified. 
130          Can return None if a producer cannot be provided or is not convenient. 
131          """ 
132          self._check() 
133          return self._source.produce(consumer, fromOffset or self._offset) 
134   
135 -    def close(self): 
136          self._check() 
137          self._source.close() 
138          self._source = None 
139   
140 -    def getLogFields(self): 
141          return self.stats.getLogFields() 
142   
143      ### Protected Methods ### 
144   
145 -    def _check(self): 
146          if self._source is None: 
147              raise fileprovider.FileClosedError("File Closed") 
148   
149 -    def _open(self, source): 
150          self._source = source 
151          self.mimeType = source.mimeType 
152   
153      ### Private Methods ### 
154   
155 -    def _cbUpdateOffset(self, data): 
156          self._reading = False 
157          self._offset += len(data) 
158          return data 
159