# -*- coding: utf-8 -*-
# couch.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 .
"""A U1DB backend that uses CouchDB as its persistence layer."""
import simplejson as json
import re
import uuid
import logging
import binascii
import socket
import time
import sys
from StringIO import StringIO
from couchdb.client import Server
from couchdb.http import (
ResourceConflict,
ResourceNotFound,
ServerError,
Session,
)
from u1db import query_parser, vectorclock
from u1db.errors import (
DatabaseDoesNotExist,
InvalidGeneration,
RevisionConflict,
InvalidDocId,
ConflictedDoc,
DocumentDoesNotExist,
DocumentAlreadyDeleted,
Unauthorized,
)
from u1db.backends import CommonBackend, CommonSyncTarget
from u1db.remote import http_app
from u1db.remote.server_state import ServerState
from leap.soledad.common import USER_DB_PREFIX, ddocs, errors
from leap.soledad.common.document import SoledadDocument
logger = logging.getLogger(__name__)
COUCH_TIMEOUT = 120 # timeout for transfers between Soledad server and Couch
class InvalidURLError(Exception):
"""
Exception raised when Soledad encounters a malformed URL.
"""
class CouchDocument(SoledadDocument):
"""
This is the document used for maintaining the Couch backend.
A CouchDocument can fetch and manipulate conflicts and also holds a
reference to the couch document revision. This data is used to ensure an
atomic and consistent update of the database.
"""
def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False,
syncable=True):
"""
Container for handling a document that is stored in couch backend.
:param doc_id: The unique document identifier.
:type doc_id: str
:param rev: The revision identifier of the document.
:type rev: str
:param json: The JSON string for this document.
:type json: str
:param has_conflicts: Boolean indicating if this document has conflicts
:type has_conflicts: bool
:param syncable: Should this document be synced with remote replicas?
:type syncable: bool
"""
SoledadDocument.__init__(self, doc_id, rev, json, has_conflicts)
self._couch_rev = None
self._conflicts = None
self._transactions = None
def _ensure_fetch_conflicts(self, get_conflicts_fun):
"""
Ensure conflict data has been fetched from the server.
:param get_conflicts_fun: A function which, given the document id and
the couch revision, return the conflicted
versions of the current document.
:type get_conflicts_fun: function
"""
if self._conflicts is None:
self._conflicts = get_conflicts_fun(self.doc_id,
couch_rev=self.couch_rev)
self.has_conflicts = len(self._conflicts) > 0
def get_conflicts(self):
"""
Get the conflicted versions of the document.
:return: The conflicted versions of the document.
:rtype: [CouchDocument]
"""
return self._conflicts
def set_conflicts(self, conflicts):
"""
Set the conflicted versions of the document.
:param conflicts: The conflicted versions of the document.
:type conflicts: list
"""
self._conflicts = conflicts
self.has_conflicts = len(self._conflicts) > 0
def add_conflict(self, doc):
"""
Add a conflict to this document.
:param doc: The conflicted version to be added.
:type doc: CouchDocument
"""
if self._conflicts is None:
raise Exception("Run self._ensure_fetch_conflicts first!")
self._conflicts.append(doc)
self.has_conflicts = len(self._conflicts) > 0
def delete_conflicts(self, conflict_revs):
"""
Delete conflicted versions of this document.
:param conflict_revs: The conflicted revisions to be deleted.
:type conflict_revs: [str]
"""
if self._conflicts is None:
raise Exception("Run self._ensure_fetch_conflicts first!")
conflicts_len = len(self._conflicts)
self._conflicts = filter(
lambda doc: doc.rev not in conflict_revs,
self._conflicts)
self.has_conflicts = len(self._conflicts) > 0
def _get_couch_rev(self):
return self._couch_rev
def _set_couch_rev(self, rev):
self._couch_rev = rev
couch_rev = property(_get_couch_rev, _set_couch_rev)
def _get_transactions(self):
return self._transactions
def _set_transactions(self, rev):
self._transactions = rev
transactions = property(_get_transactions, _set_transactions)
# monkey-patch the u1db http app to use CouchDocument
http_app.Document = CouchDocument
def raise_missing_design_doc_error(exc, ddoc_path):
"""
Raise an appropriate exception when catching a ResourceNotFound when
accessing a design document.
:param exc: The exception cought.
:type exc: ResourceNotFound
:param ddoc_path: A list representing the requested path.
:type ddoc_path: list
:raise MissingDesignDocError: Raised when tried to access a missing design
document.
:raise MissingDesignDocListFunctionError: Raised when trying to access a
missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a design
document for an yet unknown reason.
"""
path = "".join(ddoc_path)
if exc.message[1] == 'missing':
raise errors.MissingDesignDocError(path)
elif exc.message[1] == 'missing function' or \
exc.message[1].startswith('missing lists function'):
raise errors.MissingDesignDocListFunctionError(path)
elif exc.message[1] == 'missing_named_view':
raise errors.MissingDesignDocNamedViewError(path)
elif exc.message[1] == 'deleted':
raise errors.MissingDesignDocDeletedError(path)
# other errors are unknown for now
raise errors.DesignDocUnknownError("%s: %s" % (path, str(exc.message)))
def raise_server_error(exc, ddoc_path):
"""
Raise an appropriate exception when catching a ServerError when
accessing a design document.
:param exc: The exception cought.
:type exc: ResourceNotFound
:param ddoc_path: A list representing the requested path.
:type ddoc_path: list
:raise MissingDesignDocListFunctionError: Raised when trying to access a
missing list function on a
design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a design
document for an yet unknown reason.
"""
path = "".join(ddoc_path)
if exc.message[1][0] == 'unnamed_error':
raise errors.MissingDesignDocListFunctionError(path)
# other errors are unknown for now
raise errors.DesignDocUnknownError(path)
class MultipartWriter(object):
"""
A multipart writer adapted from python-couchdb's one so we can PUT
documents using couch's multipart PUT.
This stripped down version does not allow for nested structures, and
contains only the essential things we need to PUT SoledadDocuments to the
couch backend.
"""
CRLF = '\r\n'
def __init__(self, fileobj, headers=None, boundary=None):
"""
Initialize the multipart writer.
"""
self.fileobj = fileobj
if boundary is None:
boundary = self._make_boundary()
self._boundary = boundary
self._build_headers('related', headers)
def add(self, mimetype, content, headers={}):
"""
Add a part to the multipart stream.
"""
self.fileobj.write('--')
self.fileobj.write(self._boundary)
self.fileobj.write(self.CRLF)
headers['Content-Type'] = mimetype
self._write_headers(headers)
if content:
# XXX: throw an exception if a boundary appears in the content??
self.fileobj.write(content)
self.fileobj.write(self.CRLF)
def close(self):
"""
Close the multipart stream.
"""
self.fileobj.write('--')
self.fileobj.write(self._boundary)
# be careful not to have anything after '--', otherwise old couch
# versions (including bigcouch) will fail.
self.fileobj.write('--')
def _make_boundary(self):
"""
Create a boundary to discern multi parts.
"""
try:
from uuid import uuid4
return '==' + uuid4().hex + '=='
except ImportError:
from random import randrange
token = randrange(sys.maxint)
format = '%%0%dd' % len(repr(sys.maxint - 1))
return '===============' + (format % token) + '=='
def _write_headers(self, headers):
"""
Write a part header in the buffer stream.
"""
if headers:
for name in sorted(headers.keys()):
value = headers[name]
self.fileobj.write(name)
self.fileobj.write(': ')
self.fileobj.write(value)
self.fileobj.write(self.CRLF)
self.fileobj.write(self.CRLF)
def _build_headers(self, subtype, headers):
"""
Build the main headers of the multipart stream.
This is here so we can send headers separete from content using
python-couchdb API.
"""
self.headers = {}
self.headers['Content-Type'] = 'multipart/%s; boundary="%s"' % \
(subtype, self._boundary)
if headers:
for name in sorted(headers.keys()):
value = headers[name]
self.headers[name] = value
class CouchDatabase(CommonBackend):
"""
A U1DB implementation that uses CouchDB as its persistence layer.
"""
@classmethod
def open_database(cls, url, create):
"""
Open a U1DB database using CouchDB as backend.
:param url: the url of the database replica
:type url: str
:param create: should the replica be created if it does not exist?
:type create: bool
:return: the database instance
:rtype: CouchDatabase
"""
# get database from url
m = re.match('(^https?://[^/]+)/(.+)$', url)
if not m:
raise InvalidURLError
url = m.group(1)
dbname = m.group(2)
server = Server(url=url)
try:
server[dbname]
except ResourceNotFound:
if not create:
raise DatabaseDoesNotExist()
return cls(url, dbname)
def __init__(self, url, dbname, replica_uid=None, full_commit=True,
session=None, ensure_ddocs=True):
"""
Create a new Couch data container.
:param url: the url of the couch database
:type url: str
:param dbname: the database name
:type dbname: str
:param replica_uid: an optional unique replica identifier
:type replica_uid: str
:param full_commit: turn on the X-Couch-Full-Commit header
:type full_commit: bool
:param session: an http.Session instance or None for a default session
:type session: http.Session
:param ensure_ddocs: Ensure that the design docs exist on server.
:type ensure_ddocs: bool
"""
# save params
self._url = url
self._full_commit = full_commit
if session is None:
session = Session(timeout=COUCH_TIMEOUT)
self._session = session
self._factory = CouchDocument
self._real_replica_uid = None
# configure couch
self._server = Server(url=self._url,
full_commit=self._full_commit,
session=self._session)
self._dbname = dbname
try:
self._database = self._server[self._dbname]
except ResourceNotFound:
self._server.create(self._dbname)
self._database = self._server[self._dbname]
if replica_uid is not None:
self._set_replica_uid(replica_uid)
if ensure_ddocs:
self.ensure_ddocs_on_db()
def ensure_ddocs_on_db(self):
"""
Ensure that the design documents used by the backend exist on the
couch database.
"""
# we check for existence of one of the files, and put all of them if
# that one does not exist
try:
self._database['_design/docs']
return
except ResourceNotFound:
for ddoc_name in ['docs', 'syncs', 'transactions']:
ddoc = json.loads(
binascii.a2b_base64(
getattr(ddocs, ddoc_name)))
self._database.save(ddoc)
def get_sync_target(self):
"""
Return a SyncTarget object, for another u1db to synchronize with.
:return: The sync target.
:rtype: CouchSyncTarget
"""
return CouchSyncTarget(self)
def delete_database(self):
"""
Delete a U1DB CouchDB database.
"""
del(self._server[self._dbname])
def close(self):
"""
Release any resources associated with this database.
:return: True if db was succesfully closed.
:rtype: bool
"""
self._url = None
self._full_commit = None
self._session = None
self._server = None
self._database = None
return True
def _set_replica_uid(self, replica_uid):
"""
Force the replica uid to be set.
:param replica_uid: The new replica uid.
:type replica_uid: str
"""
try:
# set on existent config document
doc = self._database['u1db_config']
doc['replica_uid'] = replica_uid
except ResourceNotFound:
# or create the config document
doc = {
'_id': 'u1db_config',
'replica_uid': replica_uid,
}
self._database.save(doc)
self._real_replica_uid = replica_uid
def _get_replica_uid(self):
"""
Get the replica uid.
:return: The replica uid.
:rtype: str
"""
if self._real_replica_uid is not None:
return self._real_replica_uid
try:
# grab replica_uid from server
doc = self._database['u1db_config']
self._real_replica_uid = doc['replica_uid']
return self._real_replica_uid
except ResourceNotFound:
# create a unique replica_uid
self._real_replica_uid = uuid.uuid4().hex
self._set_replica_uid(self._real_replica_uid)
return self._real_replica_uid
_replica_uid = property(_get_replica_uid, _set_replica_uid)
def _get_generation(self):
"""
Return the current generation.
:return: The current generation.
:rtype: int
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
# query a couch list function
ddoc_path = ['_design', 'transactions', '_list', 'generation', 'log']
res = self._database.resource(*ddoc_path)
try:
response = res.get_json()
return response[2]['generation']
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
except ServerError as e:
raise_server_error(e, ddoc_path)
def _get_generation_info(self):
"""
Return the current generation.
:return: A tuple containing the current generation and transaction id.
:rtype: (int, str)
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
# query a couch list function
ddoc_path = ['_design', 'transactions', '_list', 'generation', 'log']
res = self._database.resource(*ddoc_path)
try:
response = res.get_json()
return (response[2]['generation'], response[2]['transaction_id'])
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
except ServerError as e:
raise_server_error(e, ddoc_path)
def _get_trans_id_for_gen(self, generation):
"""
Get the transaction id corresponding to a particular generation.
:param generation: The generation for which to get the transaction id.
:type generation: int
:return: The transaction id for C{generation}.
:rtype: str
:raise InvalidGeneration: Raised when the generation does not exist.
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
if generation == 0:
return ''
# query a couch list function
ddoc_path = [
'_design', 'transactions', '_list', 'trans_id_for_gen', 'log'
]
res = self._database.resource(*ddoc_path)
try:
response = res.get_json(gen=generation)
if response[2] == {}:
raise InvalidGeneration
return response[2]['transaction_id']
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
except ServerError as e:
raise_server_error(e, ddoc_path)
def _get_transaction_log(self):
"""
This is only for the test suite, it is not part of the api.
:return: The complete transaction log.
:rtype: [(str, str)]
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
# query a couch view
ddoc_path = ['_design', 'transactions', '_view', 'log']
res = self._database.resource(*ddoc_path)
try:
response = res.get_json()
return map(
lambda row: (row['id'], row['value']),
response[2]['rows'])
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
def _get_doc(self, doc_id, check_for_conflicts=False):
"""
Extract the document from storage.
This can return None if the document doesn't exist.
:param doc_id: The unique document identifier
:type doc_id: str
:param check_for_conflicts: If set to False, then the conflict check
will be skipped.
:type check_for_conflicts: bool
:return: The document.
:rtype: CouchDocument
"""
# get document with all attachments (u1db content and eventual
# conflicts)
try:
result = \
self._database.resource(doc_id).get_json(
attachments=True)[2]
except ResourceNotFound:
return None
# restrict to u1db documents
if 'u1db_rev' not in result:
return None
doc = self._factory(doc_id, result['u1db_rev'])
# set contents or make tombstone
if '_attachments' not in result \
or 'u1db_content' not in result['_attachments']:
doc.make_tombstone()
else:
doc.content = json.loads(
binascii.a2b_base64(
result['_attachments']['u1db_content']['data']))
# determine if there are conflicts
if check_for_conflicts \
and '_attachments' in result \
and 'u1db_conflicts' in result['_attachments']:
doc.has_conflicts = True
doc.set_conflicts(
self._build_conflicts(
doc.doc_id,
json.loads(binascii.a2b_base64(
result['_attachments']['u1db_conflicts']['data']))))
# store couch revision
doc.couch_rev = result['_rev']
# store transactions
doc.transactions = result['u1db_transactions']
return doc
def get_doc(self, doc_id, include_deleted=False):
"""
Get the JSON string for the given document.
:param doc_id: The unique document identifier
:type doc_id: str
:param include_deleted: If set to True, deleted documents will be
returned with empty content. Otherwise asking for a deleted
document will return None.
:type include_deleted: bool
:return: A document object.
:rtype: CouchDocument.
"""
doc = self._get_doc(doc_id, check_for_conflicts=True)
if doc is None:
return None
if doc.is_tombstone() and not include_deleted:
return None
return doc
def get_all_docs(self, include_deleted=False):
"""
Get the JSON content for all documents in the database.
:param include_deleted: If set to True, deleted documents will be
returned with empty content. Otherwise deleted
documents will not be included in the results.
:type include_deleted: bool
:return: (generation, [CouchDocument])
The current generation of the database, followed by a list of all
the documents in the database.
:rtype: (int, [CouchDocument])
"""
generation = self._get_generation()
results = []
for row in self._database.view('_all_docs'):
doc = self.get_doc(row.id, include_deleted=include_deleted)
if doc is not None:
results.append(doc)
return (generation, results)
def _put_doc(self, old_doc, doc):
"""
Put the document in the Couch backend database.
Note that C{old_doc} must have been fetched with the parameter
C{check_for_conflicts} equal to True, so we can properly update the
new document using the conflict information from the old one.
:param old_doc: The old document version.
:type old_doc: CouchDocument
:param doc: The document to be put.
:type doc: CouchDocument
:raise RevisionConflict: Raised when trying to update a document but
couch revisions mismatch.
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
attachments = {} # we save content and conflicts as attachments
parts = [] # and we put it using couch's multipart PUT
# save content as attachment
if doc.is_tombstone() is False:
content = doc.get_json()
attachments['u1db_content'] = {
'follows': True,
'content_type': 'application/octet-stream',
'length': len(content),
}
parts.append(content)
# save conflicts as attachment
if doc.has_conflicts is True:
conflicts = json.dumps(
map(lambda cdoc: (cdoc.rev, cdoc.content),
doc.get_conflicts()))
attachments['u1db_conflicts'] = {
'follows': True,
'content_type': 'application/octet-stream',
'length': len(conflicts),
}
parts.append(conflicts)
# store old transactions, if any
transactions = old_doc.transactions[:] if old_doc is not None else []
# create a new transaction id and timestamp it so the transaction log
# is consistent when querying the database.
transactions.append(
# here we store milliseconds to keep consistent with javascript
# Date.prototype.getTime() which was used before inside a couchdb
# update handler.
(int(time.time() * 1000),
self._allocate_transaction_id()))
# build the couch document
couch_doc = {
'_id': doc.doc_id,
'u1db_rev': doc.rev,
'u1db_transactions': transactions,
'_attachments': attachments,
}
# if we are updating a doc we have to add the couch doc revision
if old_doc is not None:
couch_doc['_rev'] = old_doc.couch_rev
# prepare the multipart PUT
buf = StringIO()
envelope = MultipartWriter(buf)
envelope.add('application/json', json.dumps(couch_doc))
for part in parts:
envelope.add('application/octet-stream', part)
envelope.close()
# try to save and fail if there's a revision conflict
try:
self._database.resource.put_json(
doc.doc_id, body=buf.getvalue(), headers=envelope.headers)
except ResourceConflict:
raise RevisionConflict()
def put_doc(self, doc):
"""
Update a document.
If the document currently has conflicts, put will fail.
If the database specifies a maximum document size and the document
exceeds it, put will fail and raise a DocumentTooBig exception.
:param doc: A Document with new content.
:return: new_doc_rev - The new revision identifier for the document.
The Document object will also be updated.
:raise InvalidDocId: Raised if the document's id is invalid.
:raise DocumentTooBig: Raised if the document size is too big.
:raise ConflictedDoc: Raised if the document has conflicts.
"""
if doc.doc_id is None:
raise InvalidDocId()
self._check_doc_id(doc.doc_id)
self._check_doc_size(doc)
old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
if old_doc and old_doc.has_conflicts:
raise ConflictedDoc()
if old_doc and doc.rev is None and old_doc.is_tombstone():
new_rev = self._allocate_doc_rev(old_doc.rev)
else:
if old_doc is not None:
if old_doc.rev != doc.rev:
raise RevisionConflict()
else:
if doc.rev is not None:
raise RevisionConflict()
new_rev = self._allocate_doc_rev(doc.rev)
doc.rev = new_rev
self._put_doc(old_doc, doc)
return new_rev
def whats_changed(self, old_generation=0):
"""
Return a list of documents that have changed since old_generation.
:param old_generation: The generation of the database in the old
state.
:type old_generation: int
:return: (generation, trans_id, [(doc_id, generation, trans_id),...])
The current generation of the database, its associated
transaction id, and a list of of changed documents since
old_generation, represented by tuples with for each document
its doc_id and the generation and transaction id corresponding
to the last intervening change and sorted by generation (old
changes first)
:rtype: (int, str, [(str, int, str)])
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
# query a couch list function
ddoc_path = [
'_design', 'transactions', '_list', 'whats_changed', 'log'
]
res = self._database.resource(*ddoc_path)
try:
response = res.get_json(old_gen=old_generation)
results = map(
lambda row:
(row['generation'], row['doc_id'], row['transaction_id']),
response[2]['transactions'])
results.reverse()
cur_gen = old_generation
seen = set()
changes = []
newest_trans_id = ''
for generation, doc_id, trans_id in results:
if doc_id not in seen:
changes.append((doc_id, generation, trans_id))
seen.add(doc_id)
if changes:
cur_gen = changes[0][1] # max generation
newest_trans_id = changes[0][2]
changes.reverse()
else:
cur_gen, newest_trans_id = self._get_generation_info()
return cur_gen, newest_trans_id, changes
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
except ServerError as e:
raise_server_error(e, ddoc_path)
def delete_doc(self, doc):
"""
Mark a document as deleted.
Will abort if the current revision doesn't match doc.rev.
This will also set doc.content to None.
:param doc: The document to mark as deleted.
:type doc: CouchDocument.
:raise DocumentDoesNotExist: Raised if the document does not
exist.
:raise RevisionConflict: Raised if the revisions do not match.
:raise DocumentAlreadyDeleted: Raised if the document is
already deleted.
:raise ConflictedDoc: Raised if the doc has conflicts.
"""
old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
if old_doc is None:
raise DocumentDoesNotExist
if old_doc.rev != doc.rev:
raise RevisionConflict()
if old_doc.is_tombstone():
raise DocumentAlreadyDeleted
if old_doc.has_conflicts:
raise ConflictedDoc()
new_rev = self._allocate_doc_rev(doc.rev)
doc.rev = new_rev
doc.make_tombstone()
self._put_doc(old_doc, doc)
return new_rev
def _build_conflicts(self, doc_id, attached_conflicts):
"""
Build the conflicted documents list from the conflicts attachment
fetched from a couch document.
:param attached_conflicts: The document's conflicts as fetched from a
couch document attachment.
:type attached_conflicts: dict
"""
conflicts = []
for doc_rev, content in attached_conflicts:
doc = self._factory(doc_id, doc_rev)
if content is None:
doc.make_tombstone()
else:
doc.content = content
conflicts.append(doc)
return conflicts
def _get_conflicts(self, doc_id, couch_rev=None):
"""
Get the conflicted versions of a document.
If the C{couch_rev} parameter is not None, conflicts for a specific
document's couch revision are returned.
:param couch_rev: The couch document revision.
:type couch_rev: str
:return: A list of conflicted versions of the document.
:rtype: list
"""
# request conflicts attachment from server
params = {}
if couch_rev is not None:
params['rev'] = couch_rev # restric document's couch revision
resource = self._database.resource(doc_id, 'u1db_conflicts')
try:
response = resource.get_json(**params)
return self._build_conflicts(
doc_id, json.loads(response[2].read()))
except ResourceNotFound:
return []
def get_doc_conflicts(self, doc_id):
"""
Get the list of conflicts for the given document.
The order of the conflicts is such that the first entry is the value
that would be returned by "get_doc".
:return: A list of the document entries that are conflicted.
:rtype: [CouchDocument]
"""
conflict_docs = self._get_conflicts(doc_id)
if len(conflict_docs) == 0:
return []
this_doc = self._get_doc(doc_id, check_for_conflicts=True)
return [this_doc] + conflict_docs
def _get_replica_gen_and_trans_id(self, other_replica_uid):
"""
Return the last known generation and transaction id for the other db
replica.
When you do a synchronization with another replica, the Database keeps
track of what generation the other database replica was at, and what
the associated transaction id was. This is used to determine what data
needs to be sent, and if two databases are claiming to be the same
replica.
:param other_replica_uid: The identifier for the other replica.
:type other_replica_uid: str
:return: A tuple containing the generation and transaction id we
encountered during synchronization. If we've never
synchronized with the replica, this is (0, '').
:rtype: (int, str)
"""
# query a couch view
result = self._database.view('syncs/log')
if len(result[other_replica_uid].rows) == 0:
return (0, '')
return (
result[other_replica_uid].rows[0]['value']['known_generation'],
result[other_replica_uid].rows[0]['value']['known_transaction_id']
)
def _set_replica_gen_and_trans_id(self, other_replica_uid,
other_generation, other_transaction_id):
"""
Set the last-known generation and transaction id for the other
database replica.
We have just performed some synchronization, and we want to track what
generation the other replica was at. See also
_get_replica_gen_and_trans_id.
:param other_replica_uid: The U1DB identifier for the other replica.
:type other_replica_uid: str
:param other_generation: The generation number for the other replica.
:type other_generation: int
:param other_transaction_id: The transaction id associated with the
generation.
:type other_transaction_id: str
"""
self._do_set_replica_gen_and_trans_id(
other_replica_uid, other_generation, other_transaction_id)
def _do_set_replica_gen_and_trans_id(
self, other_replica_uid, other_generation, other_transaction_id):
"""
Set the last-known generation and transaction id for the other
database replica.
We have just performed some synchronization, and we want to track what
generation the other replica was at. See also
_get_replica_gen_and_trans_id.
:param other_replica_uid: The U1DB identifier for the other replica.
:type other_replica_uid: str
:param other_generation: The generation number for the other replica.
:type other_generation: int
:param other_transaction_id: The transaction id associated with the
generation.
:type other_transaction_id: str
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
# query a couch update function
ddoc_path = ['_design', 'syncs', '_update', 'put', 'u1db_sync_log']
res = self._database.resource(*ddoc_path)
try:
res.put_json(
body={
'other_replica_uid': other_replica_uid,
'other_generation': other_generation,
'other_transaction_id': other_transaction_id,
},
headers={'content-type': 'application/json'})
except ResourceNotFound as e:
raise_missing_design_doc_error(e, ddoc_path)
def _add_conflict(self, doc, my_doc_rev, my_content):
"""
Add a conflict to the document.
Note that this method does not actually update the backend; rather, it
updates the CouchDocument object which will provide the conflict data
when the atomic document update is made.
:param doc: The document to have conflicts added to.
:type doc: CouchDocument
:param my_doc_rev: The revision of the conflicted document.
:type my_doc_rev: str
:param my_content: The content of the conflicted document as a JSON
serialized string.
:type my_content: str
"""
doc._ensure_fetch_conflicts(self._get_conflicts)
doc.add_conflict(
self._factory(doc_id=doc.doc_id, rev=my_doc_rev,
json=my_content))
def _delete_conflicts(self, doc, conflict_revs):
"""
Delete the conflicted revisions from the list of conflicts of C{doc}.
Note that this method does not actually update the backend; rather, it
updates the CouchDocument object which will provide the conflict data
when the atomic document update is made.
:param doc: The document to have conflicts deleted.
:type doc: CouchDocument
:param conflict_revs: A list of the revisions to be deleted.
:param conflict_revs: [str]
"""
doc._ensure_fetch_conflicts(self._get_conflicts)
doc.delete_conflicts(conflict_revs)
def _prune_conflicts(self, doc, doc_vcr):
"""
Prune conflicts that are older then the current document's revision, or
whose content match to the current document's content.
:param doc: The document to have conflicts pruned.
:type doc: CouchDocument
:param doc_vcr: A vector clock representing the current document's
revision.
:type doc_vcr: u1db.vectorclock.VectorClock
"""
if doc.has_conflicts is True:
autoresolved = False
c_revs_to_prune = []
for c_doc in doc.get_conflicts():
c_vcr = vectorclock.VectorClockRev(c_doc.rev)
if doc_vcr.is_newer(c_vcr):
c_revs_to_prune.append(c_doc.rev)
elif doc.same_content_as(c_doc):
c_revs_to_prune.append(c_doc.rev)
doc_vcr.maximize(c_vcr)
autoresolved = True
if autoresolved:
doc_vcr.increment(self._replica_uid)
doc.rev = doc_vcr.as_str()
self._delete_conflicts(doc, c_revs_to_prune)
def _force_doc_sync_conflict(self, doc):
"""
Add a conflict and force a document put.
:param doc: The document to be put.
:type doc: CouchDocument
"""
my_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
self._prune_conflicts(doc, vectorclock.VectorClockRev(doc.rev))
self._add_conflict(doc, my_doc.rev, my_doc.get_json())
doc.has_conflicts = True
self._put_doc(my_doc, doc)
def resolve_doc(self, doc, conflicted_doc_revs):
"""
Mark a document as no longer conflicted.
We take the list of revisions that the client knows about that it is
superseding. This may be a different list from the actual current
conflicts, in which case only those are removed as conflicted. This
may fail if the conflict list is significantly different from the
supplied information. (sync could have happened in the background from
the time you GET_DOC_CONFLICTS until the point where you RESOLVE)
:param doc: A Document with the new content to be inserted.
:type doc: CouchDocument
:param conflicted_doc_revs: A list of revisions that the new content
supersedes.
:type conflicted_doc_revs: [str]
:raise MissingDesignDocError: Raised when tried to access a missing
design document.
:raise MissingDesignDocListFunctionError: Raised when trying to access
a missing list function on a
design document.
:raise MissingDesignDocNamedViewError: Raised when trying to access a
missing named view on a design
document.
:raise MissingDesignDocDeletedError: Raised when trying to access a
deleted design document.
:raise MissingDesignDocUnknownError: Raised when failed to access a
design document for an yet
unknown reason.
"""
cur_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
new_rev = self._ensure_maximal_rev(cur_doc.rev,
conflicted_doc_revs)
superseded_revs = set(conflicted_doc_revs)
doc.rev = new_rev
# this backend stores conflicts as properties of the documents, so we
# have to copy these conflicts over to the document being updated.
if cur_doc.rev in superseded_revs:
# the newer doc version will supersede the one in the database, so
# we copy conflicts before updating the backend.
doc.set_conflicts(cur_doc.get_conflicts()) # copy conflicts over.
self._delete_conflicts(doc, superseded_revs)
self._put_doc(cur_doc, doc)
else:
# the newer doc version does not supersede the one in the
# database, so we will add a conflict to the database and copy
# those over to the document the user has in her hands.
self._add_conflict(cur_doc, new_rev, doc.get_json())
self._delete_conflicts(cur_doc, superseded_revs)
self._put_doc(cur_doc, cur_doc) # just update conflicts
# backend has been updated with current conflicts, now copy them
# to the current document.
doc.set_conflicts(cur_doc.get_conflicts())
def _put_doc_if_newer(self, doc, save_conflict, replica_uid, replica_gen,
replica_trans_id=''):
"""
Insert/update document into the database with a given revision.
This api is used during synchronization operations.
If a document would conflict and save_conflict is set to True, the
content will be selected as the 'current' content for doc.doc_id,
even though doc.rev doesn't supersede the currently stored revision.
The currently stored document will be added to the list of conflict
alternatives for the given doc_id.
This forces the new content to be 'current' so that we get convergence
after synchronizing, even if people don't resolve conflicts. Users can
then notice that their content is out of date, update it, and
synchronize again. (The alternative is that users could synchronize and
think the data has propagated, but their local copy looks fine, and the
remote copy is never updated again.)
:param doc: A document object
:type doc: CouchDocument
:param save_conflict: If this document is a conflict, do you want to
save it as a conflict, or just ignore it.
:type save_conflict: bool
:param replica_uid: A unique replica identifier.
:type replica_uid: str
:param replica_gen: The generation of the replica corresponding to the
this document. The replica arguments are optional,
but are used during synchronization.
:type replica_gen: int
:param replica_trans_id: The transaction_id associated with the
generation.
:type replica_trans_id: str
:return: (state, at_gen) - If we don't have doc_id already, or if
doc_rev supersedes the existing document revision, then the
content will be inserted, and state is 'inserted'. If
doc_rev is less than or equal to the existing revision, then
the put is ignored and state is respecitvely 'superseded' or
'converged'. If doc_rev is not strictly superseded or
supersedes, then state is 'conflicted'. The document will not
be inserted if save_conflict is False. For 'inserted' or
'converged', at_gen is the insertion/current generation.
:rtype: (str, int)
"""
cur_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
# at this point, `doc` has arrived from the other syncing party, and
# we will decide what to do with it.
# First, we prepare the arriving doc to update couch database.
old_doc = doc
doc = self._factory(doc.doc_id, doc.rev, doc.get_json())
if cur_doc is not None:
doc.couch_rev = cur_doc.couch_rev
# fetch conflicts because we will eventually manipulate them
doc._ensure_fetch_conflicts(self._get_conflicts)
# from now on, it works just like u1db sqlite backend
doc_vcr = vectorclock.VectorClockRev(doc.rev)
if cur_doc is None:
cur_vcr = vectorclock.VectorClockRev(None)
else:
cur_vcr = vectorclock.VectorClockRev(cur_doc.rev)
self._validate_source(replica_uid, replica_gen, replica_trans_id)
if doc_vcr.is_newer(cur_vcr):
rev = doc.rev
self._prune_conflicts(doc, doc_vcr)
if doc.rev != rev:
# conflicts have been autoresolved
state = 'superseded'
else:
state = 'inserted'
self._put_doc(cur_doc, doc)
elif doc.rev == cur_doc.rev:
# magical convergence
state = 'converged'
elif cur_vcr.is_newer(doc_vcr):
# Don't add this to seen_ids, because we have something newer,
# so we should send it back, and we should not generate a
# conflict
state = 'superseded'
elif cur_doc.same_content_as(doc):
# the documents have been edited to the same thing at both ends
doc_vcr.maximize(cur_vcr)
doc_vcr.increment(self._replica_uid)
doc.rev = doc_vcr.as_str()
self._put_doc(cur_doc, doc)
state = 'superseded'
else:
state = 'conflicted'
if save_conflict:
self._force_doc_sync_conflict(doc)
if replica_uid is not None and replica_gen is not None:
self._do_set_replica_gen_and_trans_id(
replica_uid, replica_gen, replica_trans_id)
# update info
old_doc.rev = doc.rev
if doc.is_tombstone():
old_doc.is_tombstone()
else:
old_doc.content = doc.content
old_doc.has_conflicts = doc.has_conflicts
return state, self._get_generation()
class CouchSyncTarget(CommonSyncTarget):
"""
Functionality for using a CouchDatabase as a synchronization target.
"""
def get_sync_info(self, source_replica_uid):
source_gen, source_trans_id = self._db._get_replica_gen_and_trans_id(
source_replica_uid)
my_gen, my_trans_id = self._db._get_generation_info()
return (
self._db._replica_uid, my_gen, my_trans_id, source_gen,
source_trans_id)
def record_sync_info(self, source_replica_uid, source_replica_generation,
source_replica_transaction_id):
if self._trace_hook:
self._trace_hook('record_sync_info')
self._db._set_replica_gen_and_trans_id(
source_replica_uid, source_replica_generation,
source_replica_transaction_id)
class NotEnoughCouchPermissions(Exception):
"""
Raised when failing to assert for enough permissions on underlying Couch
Database.
"""
pass
class CouchServerState(ServerState):
"""
Inteface of the WSGI server with the CouchDB backend.
"""
def __init__(self, couch_url, shared_db_name, tokens_db_name):
"""
Initialize the couch server state.
:param couch_url: The URL for the couch database.
:type couch_url: str
:param shared_db_name: The name of the shared database.
:type shared_db_name: str
:param tokens_db_name: The name of the tokens database.
:type tokens_db_name: str
"""
self._couch_url = couch_url
self._shared_db_name = shared_db_name
self._tokens_db_name = tokens_db_name
try:
self._check_couch_permissions()
except NotEnoughCouchPermissions:
logger.error("Not enough permissions on underlying couch "
"database (%s)." % self._couch_url)
except (socket.error, socket.gaierror, socket.herror,
socket.timeout), e:
logger.error("Socket problem while trying to reach underlying "
"couch database: (%s, %s)." %
(self._couch_url, e))
def _check_couch_permissions(self):
"""
Assert that Soledad Server has enough permissions on the underlying
couch database.
Soledad Server has to be able to do the following in the couch server:
* Create, read and write from/to 'shared' db.
* Create, read and write from/to 'user-' dbs.
* Read from 'tokens' db.
This function tries to perform the actions above using the "low level"
couch library to ensure that Soledad Server can do everything it needs
on the underlying couch database.
:param couch_url: The URL of the couch database.
:type couch_url: str
@raise NotEnoughCouchPermissions: Raised in case there are not enough
permissions to read/write/create the needed couch databases.
:rtype: bool
"""
def _open_couch_db(dbname):
server = Server(url=self._couch_url)
try:
server[dbname]
except ResourceNotFound:
server.create(dbname)
return server[dbname]
def _create_delete_test_doc(db):
doc_id, _ = db.save({'test': 'document'})
doc = db[doc_id]
db.delete(doc)
try:
# test read/write auth for shared db
_create_delete_test_doc(
_open_couch_db(self._shared_db_name))
# test read/write auth for user- db
_create_delete_test_doc(
_open_couch_db('%stest-db' % USER_DB_PREFIX))
# test read auth for tokens db
tokensdb = _open_couch_db(self._tokens_db_name)
tokensdb.info()
except Unauthorized:
raise NotEnoughCouchPermissions(self._couch_url)
def open_database(self, dbname):
"""
Open a couch database.
:param dbname: The name of the database to open.
:type dbname: str
:return: The CouchDatabase object.
:rtype: CouchDatabase
"""
return CouchDatabase.open_database(
self._couch_url + '/' + dbname,
create=False)
def ensure_database(self, dbname):
"""
Ensure couch database exists.
Usually, this method is used by the server to ensure the existence of
a database. In our setup, the Soledad user that accesses the underlying
couch server should never have permission to create (or delete)
databases. But, in case it ever does, by raising an exception here we
have one more guarantee that no modified client will be able to
enforce creation of a database when syncing.
:param dbname: The name of the database to ensure.
:type dbname: str
:return: The CouchDatabase object and the replica uid.
:rtype: (CouchDatabase, str)
"""
raise Unauthorized()
def delete_database(self, dbname):
"""
Delete couch database.
:param dbname: The name of the database to delete.
:type dbname: str
"""
raise Unauthorized()
def _set_couch_url(self, url):
"""
Set the couchdb URL
:param url: CouchDB URL
:type url: str
"""
self._couch_url = url
def _get_couch_url(self):
"""
Return CouchDB URL
:rtype: str
"""
return self._couch_url
couch_url = property(_get_couch_url, _set_couch_url, doc='CouchDB URL')