Pending.py   [plain text]

# Copyright (C) 1998-2003 by the Free Software Foundation, Inc.
#
# This program 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 2
# of the License, or (at your option) any later version.
#
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

""" Track pending confirmation of subscriptions.

new(stuff...) places an item's data in the db, returning its cookie.

confirmed(cookie) returns a tuple for the data, removing the item
from the db.  It returns None if the cookie is not registered.
"""

import os
import time
import sha
import marshal
import cPickle
import random
import errno

from Mailman import mm_cfg
from Mailman import LockFile

DBFILE = os.path.join(mm_cfg.DATA_DIR, 'pending.db')
PCKFILE = os.path.join(mm_cfg.DATA_DIR, 'pending.pck')
LOCKFILE = os.path.join(mm_cfg.LOCK_DIR, 'pending.lock')

# Types of pending records
SUBSCRIPTION = 'S'
UNSUBSCRIPTION = 'U'
CHANGE_OF_ADDRESS = 'C'
HELD_MESSAGE = 'H'
RE_ENABLE = 'E'

_ALLKEYS = [(x,) for x in (SUBSCRIPTION, UNSUBSCRIPTION,
                           CHANGE_OF_ADDRESS, HELD_MESSAGE,
                           RE_ENABLE,
                           )]

try:
    True, False
except NameError:
    True = 1
    False = 0



def new(*content):
    """Create a new entry in the pending database, returning cookie for it."""
    # It's a programming error if this assertion fails!  We do it this way so
    # the assert test won't fail if the sequence is empty.
    assert content[:1] in _ALLKEYS
    # Get a lock handle now, but only lock inside the loop.
    lock = LockFile.LockFile(
        LOCKFILE, withlogging=mm_cfg.PENDINGDB_LOCK_DEBUGGING)
    # We try the main loop several times. If we get a lock error somewhere
    # (for instance because someone broke the lock) we simply try again.
    retries = mm_cfg.PENDINGDB_LOCK_ATTEMPTS
    try:
        while retries:
            retries -= 1
            if not lock.locked():
                try:
                    lock.lock(timeout=mm_cfg.PENDINGDB_LOCK_TIMEOUT)
                except LockFile.TimeOutError:
                    continue
            # Load the current database
            db = _load()
            # Calculate a unique cookie.  Algorithm vetted by the Timbot.
            # time() has high resolution on Linux, clock() on Windows.  random
            # gives us about 45 bits in Python 2.2, 53 bits on Python 2.3.
            # The time and clock values basically help obscure the random
            # number generator, as does the hash calculation.  The integral
            # parts of the time values are discarded because they're the most
            # predictable bits.
            while True:
                now = time.time()
                x = random.random() + now % 1.0 + time.clock() % 1.0
                hashfood = repr(x)
                cookie = sha.new(hashfood).hexdigest()
                # We'll never get a duplicate, but we'll be anal about
                # checking anyway.
                if not db.has_key(cookie):
                    break
            # Store the content, plus the time in the future when this entry
            # will be evicted from the database, due to staleness.
            db[cookie] = content
            evictions = db.setdefault('evictions', {})
            evictions[cookie] = now + mm_cfg.PENDING_REQUEST_LIFE
            try:
                _save(db, lock)
            except LockFile.NotLockedError:
                continue
            return cookie
        else:
            # We failed to get the lock or keep it long enough to save the
            # data!
            raise LockFile.TimeOutError
    finally:
        if lock.locked():
            lock.unlock()



def confirm(cookie, expunge=True):
    """Return data for cookie, or None if not found.

    If optional expunge is True (the default), the record is also removed from
    the database.
    """
    if not expunge:
        db = _load()
        missing = []
        content = db.get(cookie, missing)
        if content is missing:
            return None
        return content
    # Get a lock handle now, but only lock inside the loop.
    lock = LockFile.LockFile(LOCKFILE,
                             withlogging=mm_cfg.PENDINGDB_LOCK_DEBUGGING)
    # We try the main loop several times. If we get a lock error somewhere
    # (for instance because someone broke the lock) we simply try again.
    retries = mm_cfg.PENDINGDB_LOCK_ATTEMPTS
    try:
        while retries:
            retries -= 1
            if not lock.locked():
               try:
                   lock.lock(timeout=mm_cfg.PENDINGDB_LOCK_TIMEOUT)
               except LockFile.TimeOutError:
                   continue
            # Load the database
            db = _load()
            missing = []
            content = db.get(cookie, missing)
            if content is missing:
                return None
            del db[cookie]
            del db['evictions'][cookie]
            try:
                _save(db, lock)
            except LockFile.NotLockedError:
                continue
            return content
        else:
            # We failed to get the lock and keep it long enough to save the
            # data!
            raise LockFile.TimeOutError
    finally:
        if lock.locked():
            lock.unlock()



def repend(cookie, data):
    # Get a lock
    lock = LockFile.LockFile(
        LOCKFILE, withlogging=mm_cfg.PENDINGDB_LOCK_DEBUGGING)
    lock.lock()
    try:
        # Load the database
        db = _load()
        db[cookie] = data
        db['evictions'][cookie] = time.time() + mm_cfg.PENDING_REQUEST_LIFE
        _save(db, lock)
    finally:
        lock.unlock()



def _load():
    # The list's lock must be acquired if you wish to alter data and save.
    #
    # First try to load the pickle file
    fp = None
    try:
        try:
            fp = open(PCKFILE)
            return cPickle.load(fp)
        except IOError, e:
            if e.errno <> errno.ENOENT: raise
            try:
                # Try to load the old DBFILE
                fp = open(DBFILE)
                return marshal.load(fp)
            except IOError, e:
                if e.errno <> errno.ENOENT: raise
                # Fresh pendings database
                return {'evictions': {}}
    finally:
        if fp:
            fp.close()



def _save(db, lock):
    # Lock must be acquired before loading the data that is now being saved.
    if not lock.locked():
        raise LockFile.NotLockedError
    evictions = db['evictions']
    now = time.time()
    for cookie, data in db.items():
        if cookie in ('evictions', 'version'):
            continue
        timestamp = evictions[cookie]
        if now > timestamp:
            # The entry is stale, so remove it.
            del db[cookie]
            del evictions[cookie]
    # Clean out any bogus eviction entries.
    for cookie in evictions.keys():
        if not db.has_key(cookie):
            del evictions[cookie]
    db['version'] = mm_cfg.PENDING_FILE_SCHEMA_VERSION
    omask = os.umask(007)
    # Always save this as a pickle (safely), and after that succeeds, blow
    # away any old marshal file.
    tmpfile = '%s.tmp.%d.%d' % (PCKFILE, os.getpid(), now)
    fp = None
    try:
        fp = open(tmpfile, 'w')
        cPickle.dump(db, fp)
        fp.close()
        fp = None
        if not lock.locked():
            # Our lock was broken?
            os.remove(tmpfile)
            raise LockFile.NotLockedError
        os.rename(tmpfile, PCKFILE)
        if os.path.exists(DBFILE):
            os.remove(DBFILE)
    finally:
        if fp:
            fp.close()
        os.umask(omask)



def _update(olddb):
    # Update an old pending_subscriptions.db database to the new format
    lock = LockFile.LockFile(LOCKFILE,
                             withlogging=mm_cfg.PENDINGDB_LOCK_DEBUGGING)
    lock.lock(timeout=mm_cfg.PENDINGDB_LOCK_TIMEOUT)
    try:
        # We don't need this entry anymore
        if olddb.has_key('lastculltime'):
            del olddb['lastculltime']
        db = _load()
        evictions = db.setdefault('evictions', {})
        for cookie, data in olddb.items():
            # The cookies used to be kept as a 6 digit integer.  We now keep
            # the cookies as a string (sha in our case, but it doesn't matter
            # for cookie matching).
            cookie = str(cookie)
            # The old format kept the content as a tuple and tacked the
            # timestamp on as the last element of the tuple.  We keep the
            # timestamps separate, but require the prepending of a record type
            # indicator.  We know that the only things that were kept in the
            # old format were subscription requests.  Also, the old request
            # format didn't have the subscription language.  Best we can do
            # here is use the server default.
            db[cookie] = (SUBSCRIPTION,) + data[:-1] + \
                         (mm_cfg.DEFAULT_SERVER_LANGUAGE,)
            # The old database format kept the timestamp as the time the
            # request was made.  The new format keeps it as the time the
            # request should be evicted.
            evictions[cookie] = data[-1] + mm_cfg.PENDING_REQUEST_LIFE
        _save(db, lock)
    finally:
        if lock.locked():
            lock.unlock()