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# This is a class which watches a maildir for new messages. It uses the
# linux dirwatcher API (if available) to look for new files. The
# .messageReceived method is invoked with the filename of the new message,
# relative to the top of the maildir (so it will look like "new/blahblah").
import os
from twisted.python import log
from twisted.application import service, internet
from twisted.internet import reactor
dnotify = None
try:
import dnotify
except:
# I'm not actually sure this log message gets recorded
log.msg("unable to import dnotify, so Maildir will use polling instead")
class NoSuchMaildir(Exception):
pass
class MaildirService(service.MultiService):
"""I watch a maildir for new messages. I should be placed as the service
child of some MultiService instance. When running, I use the linux
dirwatcher API (if available) or poll for new files in the 'new'
subdirectory of my maildir path. When I discover a new message, I invoke
my .messageReceived() method with the short filename of the new message,
so the full name of the new file can be obtained with
os.path.join(maildir, 'new', filename). messageReceived() should be
overridden by a subclass to do something useful. I will not move or
delete the file on my own: the subclass's messageReceived() should
probably do that.
"""
pollinterval = 10 # only used if we don't have DNotify
def __init__(self, basedir=None):
"""Create the Maildir watcher. BASEDIR is the maildir directory (the
one which contains new/ and tmp/)
"""
service.MultiService.__init__(self)
self.basedir = basedir
self.files = []
self.dnotify = None
def setBasedir(self, basedir):
# some users of MaildirService (scheduler.Try_Jobdir, in particular)
# don't know their basedir until setServiceParent, since it is
# relative to the buildmaster's basedir. So let them set it late. We
# don't actually need it until our own startService.
self.basedir = basedir
def startService(self):
service.MultiService.startService(self)
self.newdir = os.path.join(self.basedir, "new")
if not os.path.isdir(self.basedir) or not os.path.isdir(self.newdir):
raise NoSuchMaildir("invalid maildir '%s'" % self.basedir)
try:
if dnotify:
# we must hold an fd open on the directory, so we can get
# notified when it changes.
self.dnotify = dnotify.DNotify(self.newdir,
self.dnotify_callback,
[dnotify.DNotify.DN_CREATE])
except (IOError, OverflowError):
# IOError is probably linux<2.4.19, which doesn't support
# dnotify. OverflowError will occur on some 64-bit machines
# because of a python bug
log.msg("DNotify failed, falling back to polling")
if not self.dnotify:
t = internet.TimerService(self.pollinterval, self.poll)
t.setServiceParent(self)
self.poll()
def dnotify_callback(self):
log.msg("dnotify noticed something, now polling")
# give it a moment. I found that qmail had problems when the message
# was removed from the maildir instantly. It shouldn't, that's what
# maildirs are made for. I wasn't able to eyeball any reason for the
# problem, and safecat didn't behave the same way, but qmail reports
# "Temporary_error_on_maildir_delivery" (qmail-local.c:165,
# maildir_child() process exited with rc not in 0,2,3,4). Not sure
# why, and I'd have to hack qmail to investigate further, so it's
# easier to just wait a second before yanking the message out of new/
reactor.callLater(0.1, self.poll)
def stopService(self):
if self.dnotify:
self.dnotify.remove()
self.dnotify = None
return service.MultiService.stopService(self)
def poll(self):
assert self.basedir
# see what's new
for f in self.files:
if not os.path.isfile(os.path.join(self.newdir, f)):
self.files.remove(f)
newfiles = []
for f in os.listdir(self.newdir):
if not f in self.files:
newfiles.append(f)
self.files.extend(newfiles)
# TODO: sort by ctime, then filename, since safecat uses a rather
# fine-grained timestamp in the filename
for n in newfiles:
# TODO: consider catching exceptions in messageReceived
self.messageReceived(n)
def messageReceived(self, filename):
"""Called when a new file is noticed. Will call
self.parent.messageReceived() with a path relative to maildir/new.
Should probably be overridden in subclasses."""
self.parent.messageReceived(filename)
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