buildbot/changes/maildir.py

   1
   2 # This is a class which watches a maildir for new messages. It uses the
   3 # linux dirwatcher API (if available) to look for new files. The
   4 # .messageReceived method is invoked with the filename of the new message,
   5 # relative to the top of the maildir (so it will look like "new/blahblah").
   6
   7 import os
   8 from twisted.python import log
   9 from twisted.application import service, internet
  10 from twisted.internet import reactor
  11 dnotify = None
  12 try:
  13     import dnotify
  14 except:
  15     # I'm not actually sure this log message gets recorded
  16     log.msg("unable to import dnotify, so Maildir will use polling instead")
  17
  18 class NoSuchMaildir(Exception):
  19     pass
  20
  21 class MaildirService(service.MultiService):
  22     """I watch a maildir for new messages. I should be placed as the service
  23     child of some MultiService instance. When running, I use the linux
  24     dirwatcher API (if available) or poll for new files in the 'new'
  25     subdirectory of my maildir path. When I discover a new message, I invoke
  26     my .messageReceived() method with the short filename of the new message,
  27     so the full name of the new file can be obtained with
  28     os.path.join(maildir, 'new', filename). messageReceived() should be
  29     overridden by a subclass to do something useful. I will not move or
  30     delete the file on my own: the subclass's messageReceived() should
  31     probably do that.
  32     """
  33     pollinterval = 10  # only used if we don't have DNotify
  34
  35     def __init__(self, basedir=None):
  36         """Create the Maildir watcher. BASEDIR is the maildir directory (the
  37         one which contains new/ and tmp/)
  38         """
  39         service.MultiService.__init__(self)
  40         self.basedir = basedir
  41         self.files = []
  42         self.dnotify = None
  43
  44     def setBasedir(self, basedir):
  45         # some users of MaildirService (scheduler.Try_Jobdir, in particular)
  46         # don't know their basedir until setServiceParent, since it is
  47         # relative to the buildmaster's basedir. So let them set it late. We
  48         # don't actually need it until our own startService.
  49         self.basedir = basedir
  50
  51     def startService(self):
  52         service.MultiService.startService(self)
  53         self.newdir = os.path.join(self.basedir, "new")
  54         if not os.path.isdir(self.basedir) or not os.path.isdir(self.newdir):
  55             raise NoSuchMaildir("invalid maildir '%s'" % self.basedir)
  56         try:
  57             if dnotify:
  58                 # we must hold an fd open on the directory, so we can get
  59                 # notified when it changes.
  60                 self.dnotify = dnotify.DNotify(self.newdir,
  61                                                self.dnotify_callback,
  62                                                [dnotify.DNotify.DN_CREATE])
  63         except (IOError, OverflowError):
  64             # IOError is probably linux<2.4.19, which doesn't support
  65             # dnotify. OverflowError will occur on some 64-bit machines
  66             # because of a python bug
  67             log.msg("DNotify failed, falling back to polling")
  68         if not self.dnotify:
  69             t = internet.TimerService(self.pollinterval, self.poll)
  70             t.setServiceParent(self)
  71         self.poll()
  72
  73     def dnotify_callback(self):
  74         log.msg("dnotify noticed something, now polling")
  75
  76         # give it a moment. I found that qmail had problems when the message
  77         # was removed from the maildir instantly. It shouldn't, that's what
  78         # maildirs are made for. I wasn't able to eyeball any reason for the
  79         # problem, and safecat didn't behave the same way, but qmail reports
  80         # "Temporary_error_on_maildir_delivery" (qmail-local.c:165,
  81         # maildir_child() process exited with rc not in 0,2,3,4). Not sure
  82         # why, and I'd have to hack qmail to investigate further, so it's
  83         # easier to just wait a second before yanking the message out of new/
  84
  85         reactor.callLater(0.1, self.poll)
  86
  87
  88     def stopService(self):
  89         if self.dnotify:
  90             self.dnotify.remove()
  91             self.dnotify = None
  92         return service.MultiService.stopService(self)
  93
  94     def poll(self):
  95         assert self.basedir
  96         # see what's new
  97         for f in self.files:
  98             if not os.path.isfile(os.path.join(self.newdir, f)):
  99                 self.files.remove(f)
 100         newfiles = []
 101         for f in os.listdir(self.newdir):
 102             if not f in self.files:
 103                 newfiles.append(f)
 104         self.files.extend(newfiles)
 105         # TODO: sort by ctime, then filename, since safecat uses a rather
 106         # fine-grained timestamp in the filename
 107         for n in newfiles:
 108             # TODO: consider catching exceptions in messageReceived
 109             self.messageReceived(n)
 110
 111     def messageReceived(self, filename):
 112         """Called when a new file is noticed. Will call
 113         self.parent.messageReceived() with a path relative to maildir/new.
 114         Should probably be overridden in subclasses."""
 115         self.parent.messageReceived(filename)
 116