prototype.py 3.8 KB
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# Copyright (C) 2008-2018 by the Free Software Foundation, Inc.
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#
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# This file is part of GNU Mailman.
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#
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# GNU Mailman is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
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#
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# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
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"""Prototypical permalinking archiver."""

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import os
import logging
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from contextlib import suppress
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from datetime import timedelta
from flufl.lock import Lock, TimeOutError
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from mailbox import Maildir
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from mailman.config import config
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from mailman.interfaces.archiver import IArchiver
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from public import public
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from zope.interface import implementer

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log = logging.getLogger('mailman.error')

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@public
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@implementer(IArchiver)
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class Prototype:
    """A prototype of a third party archiver.

    Mailman proposes a draft specification for interoperability between list
    servers and archivers: <http://wiki.list.org/display/DEV/Stable+URLs>.
    """

    name = 'prototype'
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    is_enabled = False
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    @staticmethod
    def list_url(mlist):
        """See `IArchiver`."""
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        # This archiver is not web-accessible, therefore no URL is returned.
        return None
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    @staticmethod
    def permalink(mlist, msg):
        """See `IArchiver`."""
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        # This archiver is not web-accessible, therefore no URL is returned.
        return None
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    @staticmethod
    def archive_message(mlist, message):
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        """See `IArchiver`.
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        This archiver saves messages into a maildir.
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        """
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        archive_dir = os.path.join(config.ARCHIVE_DIR, 'prototype')
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        with suppress(FileExistsError):
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            os.makedirs(archive_dir, 0o775)
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        # Maildir will throw an error if the directories are partially created
        # (for instance the toplevel exists but cur, new, or tmp do not)
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        # therefore we don't create the toplevel as we did above.
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        list_dir = os.path.join(archive_dir, mlist.fqdn_listname)
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        mailbox = Maildir(list_dir, create=True, factory=None)
        lock_file = os.path.join(
            config.LOCK_DIR, '{0}-maildir.lock'.format(mlist.fqdn_listname))
        # Lock the maildir as Maildir.add() is not threadsafe.  Don't use the
        # context manager because it's not an error if we can't acquire the
        # archiver lock.  We'll just log the problem and continue.
        #
        # XXX 2012-03-14 BAW: When we extend the chain/pipeline architecture
        # to other runners, e.g. the archive runner, it would be better to let
        # any TimeOutError propagate up.  That would cause the message to be
        # re-queued and tried again later, rather than being discarded as
        # happens now below.
        lock = Lock(lock_file)
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        try:
            lock.lock(timeout=timedelta(seconds=1))
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            # Add the message to the maildir.  The return value could be used
            # to construct the file path if necessary.  E.g.
            #
            # os.path.join(archive_dir, mlist.fqdn_listname, 'new',
            #              message_key)
            mailbox.add(message)
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        except TimeOutError:
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            # Log the error and go on.
            log.error('Unable to acquire prototype archiver lock for {0}, '
                      'discarding: {1}'.format(
                          mlist.fqdn_listname,
                          message.get('message-id', 'n/a')))
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        finally:
            lock.unlock(unconditionally=True)
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        return None