[refactor] remove shared db locking from server

3 files changed, 2 insertions, 247 deletions

diff --git a/server/src/leap/soledad/server/__init__.py b/server/src/leap/soledad/server/__init__.py
index 22894dac..43554eb4 100644
--- a/server/src/leap/soledad/server/__init__.py
+++ b/server/src/leap/soledad/server/__init__.py
@@ -49,9 +49,7 @@ synchronization is handled by the `leap.soledad.server.auth` module.
 Shared database
 ---------------
 
-Each user may store password-encrypted recovery data in the shared database,
-as well as obtain a lock on the shared database in order to prevent creation
-of multiple secrets in parallel.
+Each user may store password-encrypted recovery data in the shared database.
 
 Recovery documents are stored in the database without any information that
 may identify the user. In order to achieve this, the doc_id of recovery
@@ -77,13 +75,8 @@ This has some implications:
   * Because of the above, it is recommended that recovery documents expire
     (not implemented yet) to prevent excess storage.
 
-Lock documents, on the other hand, may be more thoroughly protected by the
-server. Their doc_id's are calculated from the SHARED_DB_LOCK_DOC_ID_PREFIX
-and the user's uid.
-
 The authorization for creating, updating, deleting and retrieving recovery
-and lock documents on the shared database is handled by
-`leap.soledad.server.auth` module.
+documents on the shared database is handled by `leap.soledad.server.auth` module.
 """
 
 import configparser
@@ -96,7 +89,6 @@ from ._version import get_versions
 
 from leap.soledad.server.auth import SoledadTokenAuthMiddleware
 from leap.soledad.server.gzip_middleware import GzipMiddleware
-from leap.soledad.server.lock_resource import LockResource
 from leap.soledad.server.sync import (
     SyncResource,
     MAX_REQUEST_SIZE,
@@ -155,7 +147,6 @@ http_app.url_to_resource.register(http_app.DocsResource)
 http_app.url_to_resource.register(http_app.DocResource)
 
 # register Soledad's new or modified resources
-http_app.url_to_resource.register(LockResource)
 http_app.url_to_resource.register(SyncResource)
 
 
diff --git a/server/src/leap/soledad/server/auth.py b/server/src/leap/soledad/server/auth.py
index ccbd6fbd..0ce1f497 100644
--- a/server/src/leap/soledad/server/auth.py
+++ b/server/src/leap/soledad/server/auth.py
@@ -101,7 +101,6 @@ class URLToAuthorization(object):
             /shared-db/docs               | -
             /shared-db/doc/{any_id}       | GET, PUT, DELETE
             /shared-db/sync-from/{source} | -
-            /shared-db/lock/{uuid}        | PUT, DELETE
             /user-db                      | GET, PUT, DELETE
             /user-db/docs                 | -
             /user-db/doc/{id}             | -
@@ -118,10 +117,6 @@ class URLToAuthorization(object):
             '/%s/doc/{id:.*}' % SHARED_DB_NAME,
             [self.HTTP_METHOD_GET, self.HTTP_METHOD_PUT,
              self.HTTP_METHOD_DELETE])
-        # auth info for shared-db lock resource
-        self._register(
-            '/%s/lock/%s' % (SHARED_DB_NAME, self._uuid),
-            [self.HTTP_METHOD_PUT, self.HTTP_METHOD_DELETE])
         # auth info for user-db database resource
         self._register(
             '/%s' % self._user_db_name,
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