zeroinstall/injector/background.py

   1 """
   2 Check for updates in a background process. If we can start a program immediately, but some of our information
   3 is rather old (longer that the freshness threshold) then we run it anyway, and check for updates using a new
   4 process that runs quietly in the background.
   5
   6 This avoids the need to annoy people with a 'checking for updates' box when they're trying to run things.
   7 """
   8
   9 import sys, os
  10 from logging import info
  11 from zeroinstall.support import tasks
  12 from zeroinstall.injector.iface_cache import iface_cache
  13 from zeroinstall.injector import handler
  14
  15 # Copyright (C) 2007, Thomas Leonard
  16 # See the README file for details, or visit http://0install.net.
  17
  18 try:
  19         import dbus
  20         import dbus.glib
  21
  22         session_bus = dbus.SessionBus()
  23
  24         remote_object = session_bus.get_object('org.freedesktop.Notifications',
  25                                                 '/org/freedesktop/Notifications')
  26
  27         notification_service = dbus.Interface(remote_object,
  28                                         'org.freedesktop.Notifications')
  29
  30         # The Python bindings insist on printing a pointless introspection
  31         # warning to stderr if the service is missing. Force it to be done
  32         # now so we can skip it
  33         old_stderr = sys.stderr
  34         sys.stderr = None
  35         try:
  36                 notification_service.GetCapabilities()
  37         finally:
  38                 sys.stderr = old_stderr
  39
  40         have_notifications = True
  41 except Exception, ex:
  42         info("Failed to import D-BUS bindings: %s", ex)
  43         have_notifications = False
  44
  45 LOW = 0
  46 NORMAL = 1
  47 CRITICAL = 2
  48
  49 def _escape_xml(s):
  50         return s.replace('&', '&amp;').replace('<', '&lt;')
  51
  52 def notify(title, message, timeout = 0, actions = []):
  53         if not have_notifications:
  54                 info('%s: %s', title, message)
  55                 return None
  56
  57         import time
  58         import dbus.types
  59
  60         hints = {}
  61         if actions:
  62                 hints['urgency'] = dbus.types.Byte(NORMAL)
  63         else:
  64                 hints['urgency'] = dbus.types.Byte(LOW)
  65
  66         return notification_service.Notify('Zero Install',
  67                 0,              # replaces_id,
  68                 '',             # icon
  69                 _escape_xml(title),
  70                 _escape_xml(message),
  71                 actions,
  72                 hints,
  73                 timeout * 1000)
  74
  75 def _exec_gui(uri, *args):
  76         os.execvp('0launch', ['0launch', '--download-only', '--gui'] + list(args) + [uri])
  77
  78 class BackgroundHandler(handler.Handler):
  79         def __init__(self, title):
  80                 handler.Handler.__init__(self)
  81                 self.title = title
  82
  83         def confirm_trust_keys(self, interface, sigs, iface_xml):
  84                 notify("Zero Install", "Can't update interface; signature not yet trusted. Running GUI...", timeout = 2)
  85                 _exec_gui(interface.uri, '--refresh')
  86
  87         def report_error(self, exception):
  88                 notify("Zero Install", "Error updating %s: %s" % (self.title, str(exception)))
  89
  90 def _detach():
  91         """Fork a detached grandchild.
  92         @return: True if we are the original."""
  93         child = os.fork()
  94         if child:
  95                 pid, status = os.waitpid(child, 0)
  96                 assert pid == child
  97                 return True
  98
  99         # The calling process might be waiting for EOF from its child.
 100         # Close our stdout so we don't keep it waiting.
 101         # Note: this only fixes the most common case; it could be waiting
 102         # on any other FD as well. We should really use gobject.spawn_async
 103         # to close *all* FDs.
 104         null = os.open('/dev/null', os.O_RDWR)
 105         os.dup2(null, 1)
 106         os.close(null)
 107
 108         grandchild = os.fork()
 109         if grandchild:
 110                 os._exit(0)     # Parent's waitpid returns and grandchild continues
 111
 112         return False
 113
 114 def _check_for_updates(policy, verbose):
 115         root_iface = iface_cache.get_interface(policy.root).get_name()
 116         info("Checking for updates to '%s' in a background process", root_iface)
 117         if verbose:
 118                 notify("Zero Install", "Checking for updates to '%s'..." % root_iface, timeout = 1)
 119
 120         policy.handler = BackgroundHandler(root_iface)
 121         policy.freshness = 0                    # Don't bother trying to refresh when getting the interface
 122         refresh = policy.refresh_all()          # (causes confusing log messages)
 123         policy.handler.wait_for_blocker(refresh)
 124
 125         # We could even download the archives here, but for now just
 126         # update the interfaces.
 127
 128         if not policy.need_download():
 129                 if verbose:
 130                         notify("Zero Install", "No updates to download.", timeout = 1)
 131                 sys.exit(0)
 132
 133         if not have_notifications:
 134                 notify("Zero Install", "Updates ready to download for '%s'." % root_iface)
 135                 sys.exit(0)
 136
 137         notification_closed = tasks.Blocker("wait for notification response")
 138
 139         def _NotificationClosed(nid, *unused):
 140                 if nid != our_question: return
 141                 notification_closed.trigger()
 142
 143         def _ActionInvoked(nid, action):
 144                 if nid != our_question: return
 145                 if action == 'download':
 146                         _exec_gui(policy.root)
 147                 notification_closed.trigger()
 148
 149         notification_service.connect_to_signal('NotificationClosed', _NotificationClosed)
 150         notification_service.connect_to_signal('ActionInvoked', _ActionInvoked)
 151
 152         our_question = notify("Zero Install", "Updates ready to download for '%s'." % root_iface,
 153                                 actions = ['download', 'Download'])
 154
 155         policy.handler.wait_for_blocker(notification_closed)
 156
 157 def spawn_background_update(policy, verbose):
 158         # Mark all feeds as being updated. Do this before forking, so that if someone is
 159         # running lots of 0launch commands in series on the same program we don't start
 160         # huge numbers of processes.
 161         import time
 162         for x in policy.implementation:
 163                 iface_cache.mark_as_checking(x.uri)                     # Main feed
 164                 for f in policy.usable_feeds(x):
 165                         iface_cache.mark_as_checking(f.uri)             # Extra feeds
 166
 167         if _detach():
 168                 return
 169
 170         try:
 171                 try:
 172                         _check_for_updates(policy, verbose)
 173                 except SystemExit:
 174                         raise
 175                 except:
 176                         import traceback
 177                         traceback.print_exc()
 178                         sys.stdout.flush()
 179                 else:
 180                         sys.exit(0)
 181         finally:
 182                 os._exit(1)