Move lock resource to its own file.

2 files changed, 235 insertions, 208 deletions

diff --git a/server/src/leap/soledad/server/__init__.py b/server/src/leap/soledad/server/__init__.py
index 26c33222..b2d55fcd 100644
--- a/server/src/leap/soledad/server/__init__.py
+++ b/server/src/leap/soledad/server/__init__.py
@@ -87,10 +87,6 @@ and lock documents on the shared database is handled by
 """
 
 import configparser
-import time
-import hashlib
-import os
-import tempfile
 
 from u1db.remote import http_app
 
@@ -99,10 +95,6 @@ from u1db.remote import http_app
 from OpenSSL import tsafe
 old_tsafe = tsafe
 
-from twisted.web.wsgi import WSGIResource
-from twisted.internet import reactor
-from twisted.internet.error import TimeoutError
-from twisted.python.lockfile import FilesystemLock
 from twisted import version
 if version.base() == "12.0.0":
     # Put OpenSSL's tsafe back into place. This can probably be removed if we
@@ -112,19 +104,10 @@ if version.base() == "12.0.0":
 
 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.common import (
-    SHARED_DB_NAME,
-    SHARED_DB_LOCK_DOC_ID_PREFIX,
-)
+from leap.soledad.common import SHARED_DB_NAME
 from leap.soledad.common.couch import CouchServerState
-from leap.soledad.common.errors import (
-    InvalidTokenError,
-    NotLockedError,
-    AlreadyLockedError,
-    LockTimedOutError,
-    CouldNotObtainLockError,
-)
 
 
 #-----------------------------------------------------------------------------
@@ -159,195 +142,7 @@ class SoledadApp(http_app.HTTPApp):
         return http_app.HTTPApp.__call__(self, environ, start_response)
 
 
-#
-# LockResource: a lock based on a document in the shared database.
-#
-
-@http_app.url_to_resource.register
-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}' % SoledadApp.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(SoledadApp.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:
-            wire_descr = AlreadyLockedError.wire_description
-            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)
-            self._responder.send_response_json(200)  # success: should use 204
-                                                     # but u1db does not
-                                                     # support it.
-
-    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 Exception:
-            return False
+http_app.url_to_resource.register(LockResource)
 
 
 #-----------------------------------------------------------------------------
diff --git a/server/src/leap/soledad/server/lock_resource.py b/server/src/leap/soledad/server/lock_resource.py
new file mode 100644
index 00000000..a7870f77
--- /dev/null
+++ b/server/src/leap/soledad/server/lock_resource.py
@@ -0,0 +1,232 @@
+# -*- 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)
+            self._responder.send_response_json(200)  # success: should use 204
+                                                     # but u1db does not
+                                                     # support it.
+
+    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