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.injector.iface_cache import iface_cache
  12 from zeroinstall.injector import handler
  13
  14 # Copyright (C) 2007, Thomas Leonard
  15 # See the README file for details, or visit http://0install.net.
  16
  17 try:
  18         import dbus
  19         import dbus.glib
  20
  21         session_bus = dbus.SessionBus()
  22
  23         remote_object = session_bus.get_object('org.freedesktop.Notifications',
  24                                                 '/org/freedesktop/Notifications')
  25
  26         notification_service = dbus.Interface(remote_object,
  27                                         'org.freedesktop.Notifications')
  28
  29         # The Python bindings insist on printing a pointless introspection
  30         # warning to stderr if the service is missing. Force it to be done
  31         # now so we can skip it
  32         old_stderr = sys.stderr
  33         sys.stderr = None
  34         try:
  35                 notification_service.GetCapabilities()
  36         finally:
  37                 sys.stderr = old_stderr
  38
  39         have_notifications = True
  40 except Exception, ex:
  41         info("Failed to import D-BUS bindings: %s", ex)
  42         have_notifications = False
  43
  44 LOW = 0
  45 NORMAL = 1
  46 CRITICAL = 2
  47
  48 def _escape_xml(s):
  49         return s.replace('&', '&amp;').replace('<', '&lt;')
  50
  51 def notify(title, message, timeout = 0, actions = []):
  52         if not have_notifications:
  53                 info('%s: %s', title, message)
  54                 return None
  55
  56         import time
  57         import dbus.types
  58
  59         hints = {}
  60         if actions:
  61                 hints['urgency'] = dbus.types.Byte(NORMAL)
  62         else:
  63                 hints['urgency'] = dbus.types.Byte(LOW)
  64
  65         return notification_service.Notify('Zero Install',
  66                 0,              # replaces_id,
  67                 '',             # icon
  68                 _escape_xml(title),
  69                 _escape_xml(message),
  70                 actions,
  71                 hints,
  72                 timeout * 1000)
  73
  74 def _exec_gui(uri, *args):
  75         os.execvp('0launch', ['0launch', '--download-only', '--gui'] + list(args) + [uri])
  76
  77 class BackgroundHandler(handler.Handler):
  78         def __init__(self, title):
  79                 handler.Handler.__init__(self)
  80                 self.title = title
  81
  82         def confirm_trust_keys(self, interface, sigs, iface_xml):
  83                 notify("Zero Install", "Can't update interface; signature not yet trusted. Running GUI...", timeout = 2)
  84                 _exec_gui(interface.uri, '--refresh')
  85
  86         def report_error(self, exception):
  87                 notify("Zero Install", "Error updating %s: %s" % (self.title, str(exception)))
  88
  89 def _detach():
  90         """Fork a detached grandchild.
  91         @return: True if we are the original."""
  92         child = os.fork()
  93         if child:
  94                 pid, status = os.waitpid(child, 0)
  95                 assert pid == child
  96                 return True
  97
  98         # The calling process might be waiting for EOF from its child.
  99         # Close our stdout so we don't keep it waiting.
 100         # Note: this only fixes the most common case; it could be waiting
 101         # on any other FD as well. We should really use gobject.spawn_async
 102         # to close *all* FDs.
 103         null = os.open('/dev/null', os.O_RDWR)
 104         os.dup2(null, 1)
 105         os.close(null)
 106
 107         grandchild = os.fork()
 108         if grandchild:
 109                 os._exit(0)     # Parent's waitpid returns and grandchild continues
 110
 111         return False
 112
 113 def _check_for_updates(policy, verbose):
 114         root_iface = iface_cache.get_interface(policy.root).get_name()
 115         info("Checking for updates to '%s' in a background process", root_iface)
 116         if verbose:
 117                 notify("Zero Install", "Checking for updates to '%s'..." % root_iface, timeout = 1)
 118
 119         policy.handler = BackgroundHandler(root_iface)
 120         policy.freshness = 0            # Don't bother trying to refresh when getting the interface
 121         policy.refresh_all()            # (causes confusing log messages)
 122         policy.handler.wait_for_downloads()
 123         # We could even download the archives here, but for now just
 124         # update the interfaces.
 125
 126         if not policy.need_download():
 127                 if verbose:
 128                         notify("Zero Install", "No updates to download.", timeout = 1)
 129                 sys.exit(0)
 130
 131         if not have_notifications:
 132                 notify("Zero Install", "Updates ready to download for '%s'." % root_iface)
 133                 sys.exit(0)
 134
 135         import gobject
 136         ctx = gobject.main_context_default()
 137         loop = gobject.MainLoop(ctx)
 138
 139         def _NotificationClosed(nid, *unused):
 140                 if nid != our_question: return
 141                 loop.quit()
 142
 143         def _ActionInvoked(nid, action):
 144                 if nid != our_question: return
 145                 if action == 'download':
 146                         _exec_gui(policy.root)
 147                 loop.quit()
 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         loop.run()
 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)