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Diffstat (limited to 'server/src/leap/soledad/server/lock_resource.py')
| -rw-r--r-- | server/src/leap/soledad/server/lock_resource.py | 231 |
1 files changed, 0 insertions, 231 deletions
diff --git a/server/src/leap/soledad/server/lock_resource.py b/server/src/leap/soledad/server/lock_resource.py deleted file mode 100644 index 0a602e26..00000000 --- a/server/src/leap/soledad/server/lock_resource.py +++ /dev/null @@ -1,231 +0,0 @@ -# -*- coding: utf-8 -*- -# lock_resource.py -# Copyright (C) 2013 LEAP -# -# 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 3 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, see <http://www.gnu.org/licenses/>. - - -""" -LockResource: a lock based on a document in the shared database. -""" - - -import hashlib -import time -import os -import tempfile -import errno - - -from u1db.remote import http_app -from twisted.python.lockfile import FilesystemLock - - -from leap.soledad.common import ( - SHARED_DB_NAME, - SHARED_DB_LOCK_DOC_ID_PREFIX, -) -from leap.soledad.common.errors import ( - InvalidTokenError, - NotLockedError, - AlreadyLockedError, - LockTimedOutError, - CouldNotObtainLockError, -) - - -class LockResource(object): - """ - Handle requests for locking documents. - - This class uses Twisted's Filesystem lock to manage a lock in the shared - database. - """ - - url_pattern = '/%s/lock/{uuid}' % SHARED_DB_NAME - """ - """ - - TIMEOUT = 300 # XXX is 5 minutes reasonable? - """ - The timeout after which the lock expires. - """ - - # used for lock doc storage - TIMESTAMP_KEY = '_timestamp' - LOCK_TOKEN_KEY = '_token' - - FILESYSTEM_LOCK_TRIES = 5 - FILESYSTEM_LOCK_SLEEP_SECONDS = 1 - - def __init__(self, uuid, state, responder): - """ - Initialize the lock resource. Parameters to this constructor are - automatically passed by u1db. - - :param uuid: The user unique id. - :type uuid: str - :param state: The backend database state. - :type state: u1db.remote.ServerState - :param responder: The infrastructure to send responses to client. - :type responder: u1db.remote.HTTPResponder - """ - self._shared_db = state.open_database(SHARED_DB_NAME) - self._lock_doc_id = '%s%s' % (SHARED_DB_LOCK_DOC_ID_PREFIX, uuid) - self._lock = FilesystemLock( - os.path.join( - tempfile.gettempdir(), - hashlib.sha512(self._lock_doc_id).hexdigest())) - self._state = state - self._responder = responder - - @http_app.http_method(content=str) - def put(self, content=None): - """ - Handle a PUT request to the lock document. - - A lock is a document in the shared db with doc_id equal to - 'lock-<uuid>' and the timestamp of its creation as content. This - method obtains a threaded-lock and creates a lock document if it does - not exist or if it has expired. - - It returns '201 Created' and a pair containing a token to unlock and - the lock timeout, or '403 AlreadyLockedError' and the remaining amount - of seconds the lock will still be valid. - - :param content: The content of the PUT request. It is only here - because PUT requests with empty content are considered - invalid requests by u1db. - :type content: str - """ - # obtain filesystem lock - if not self._try_obtain_filesystem_lock(): - self._responder.send_response_json( - LockTimedOutError.status, # error: request timeout - error=LockTimedOutError.wire_description) - return - - created_lock = False - now = time.time() - token = hashlib.sha256(os.urandom(10)).hexdigest() # for releasing - lock_doc = self._shared_db.get_doc(self._lock_doc_id) - remaining = self._remaining(lock_doc, now) - - # if there's no lock, create one - if lock_doc is None: - lock_doc = self._shared_db.create_doc( - { - self.TIMESTAMP_KEY: now, - self.LOCK_TOKEN_KEY: token, - }, - doc_id=self._lock_doc_id) - created_lock = True - else: - if remaining == 0: - # lock expired, create new one - lock_doc.content = { - self.TIMESTAMP_KEY: now, - self.LOCK_TOKEN_KEY: token, - } - self._shared_db.put_doc(lock_doc) - created_lock = True - - self._try_release_filesystem_lock() - - # send response to client - if created_lock is True: - self._responder.send_response_json( - 201, timeout=self.TIMEOUT, token=token) # success: created - else: - self._responder.send_response_json( - AlreadyLockedError.status, # error: forbidden - error=AlreadyLockedError.wire_description, remaining=remaining) - - @http_app.http_method(token=str) - def delete(self, token=None): - """ - Delete the lock if the C{token} is valid. - - Delete the lock document in case C{token} is equal to the token stored - in the lock document. - - :param token: The token returned when locking. - :type token: str - - :raise NotLockedError: Raised in case the lock is not locked. - :raise InvalidTokenError: Raised in case the token is invalid for - unlocking. - """ - lock_doc = self._shared_db.get_doc(self._lock_doc_id) - if lock_doc is None or self._remaining(lock_doc, time.time()) == 0: - self._responder.send_response_json( - NotLockedError.status, # error: not found - error=NotLockedError.wire_description) - elif token != lock_doc.content[self.LOCK_TOKEN_KEY]: - self._responder.send_response_json( - InvalidTokenError.status, # error: unauthorized - error=InvalidTokenError.wire_description) - else: - self._shared_db.delete_doc(lock_doc) - # respond success: should use 204 but u1db does not support it. - self._responder.send_response_json(200) - - def _remaining(self, lock_doc, now): - """ - Return the number of seconds the lock contained in C{lock_doc} is - still valid, when compared to C{now}. - - :param lock_doc: The document containing the lock. - :type lock_doc: u1db.Document - :param now: The time to which to compare the lock timestamp. - :type now: float - - :return: The amount of seconds the lock is still valid. - :rtype: float - """ - if lock_doc is not None: - lock_timestamp = lock_doc.content[self.TIMESTAMP_KEY] - remaining = lock_timestamp + self.TIMEOUT - now - return remaining if remaining > 0 else 0.0 - return 0.0 - - def _try_obtain_filesystem_lock(self): - """ - Try to obtain the file system lock. - - @return: Whether the lock was succesfully obtained. - @rtype: bool - """ - tries = self.FILESYSTEM_LOCK_TRIES - while tries > 0: - try: - return self._lock.lock() - except OSError as e: - tries -= 1 - if tries == 0: - raise CouldNotObtainLockError(e.message) - time.sleep(self.FILESYSTEM_LOCK_SLEEP_SECONDS) - return False - - def _try_release_filesystem_lock(self): - """ - Release the filesystem lock. - """ - try: - self._lock.unlock() - return True - except OSError as e: - if e.errno == errno.ENOENT: - return True - return False |