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synapse/state.py

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+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.federation.pdu_codec import encode_event_id
+from synapse.util.logutils import log_function
+
+from collections import namedtuple
+
+import logging
+import hashlib
+
+logger = logging.getLogger(__name__)
+
+
+def _get_state_key_from_event(event):
+    return event.state_key
+
+
+KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))
+
+
+class StateHandler(object):
+    """ Repsonsible for doing state conflict resolution.
+    """
+
+    def __init__(self, hs):
+        self.store = hs.get_datastore()
+        self._replication = hs.get_replication_layer()
+        self.server_name = hs.hostname
+
+    @defer.inlineCallbacks
+    @log_function
+    def handle_new_event(self, event):
+        """ Given an event this works out if a) we have sufficient power level
+        to update the state and b) works out what the prev_state should be.
+
+        Returns:
+            Deferred: Resolved with a boolean indicating if we succesfully
+            updated the state.
+
+        Raised:
+            AuthError
+        """
+        # This needs to be done in a transaction.
+
+        if not hasattr(event, "state_key"):
+            return
+
+        key = KeyStateTuple(
+            event.room_id,
+            event.type,
+            _get_state_key_from_event(event)
+        )
+
+        # Now I need to fill out the prev state and work out if it has auth
+        # (w.r.t. to power levels)
+
+        results = yield self.store.get_latest_pdus_in_context(
+            event.room_id
+        )
+
+        event.prev_events = [
+            encode_event_id(p_id, origin) for p_id, origin, _ in results
+        ]
+        event.prev_events = [
+            e for e in event.prev_events if e != event.event_id
+        ]
+
+        if results:
+            event.depth = max([int(v) for _, _, v in results]) + 1
+        else:
+            event.depth = 0
+
+        current_state = yield self.store.get_current_state(
+            key.context, key.type, key.state_key
+        )
+
+        if current_state:
+            event.prev_state = encode_event_id(
+                current_state.pdu_id, current_state.origin
+            )
+
+        # TODO check current_state to see if the min power level is less
+        # than the power level of the user
+        # power_level = self._get_power_level_for_event(event)
+
+        yield self.store.update_current_state(
+            pdu_id=event.event_id,
+            origin=self.server_name,
+            context=key.context,
+            pdu_type=key.type,
+            state_key=key.state_key
+        )
+
+        defer.returnValue(True)
+
+    @defer.inlineCallbacks
+    @log_function
+    def handle_new_state(self, new_pdu):
+        """ Apply conflict resolution to `new_pdu`.
+
+        This should be called on every new state pdu, regardless of whether or
+        not there is a conflict.
+
+        This function is safe against the race of it getting called with two
+        `PDU`s trying to update the same state.
+        """
+
+        # This needs to be done in a transaction.
+
+        is_new = yield self._handle_new_state(new_pdu)
+
+        if is_new:
+            yield self.store.update_current_state(
+                pdu_id=new_pdu.pdu_id,
+                origin=new_pdu.origin,
+                context=new_pdu.context,
+                pdu_type=new_pdu.pdu_type,
+                state_key=new_pdu.state_key
+            )
+
+        defer.returnValue(is_new)
+
+    def _get_power_level_for_event(self, event):
+        # return self._persistence.get_power_level_for_user(event.room_id,
+            # event.sender)
+        return event.power_level
+
+    @defer.inlineCallbacks
+    @log_function
+    def _handle_new_state(self, new_pdu):
+        tree = yield self.store.get_unresolved_state_tree(new_pdu)
+        new_branch, current_branch = tree
+
+        logger.debug(
+            "_handle_new_state new=%s, current=%s",
+            new_branch, current_branch
+        )
+
+        if not current_branch:
+            # There is no current state
+            defer.returnValue(True)
+            return
+
+        if new_branch[-1] == current_branch[-1]:
+            # We have all the PDUs we need, so we can just do the conflict
+            # resolution.
+
+            if len(current_branch) == 1:
+                # This is a direct clobber so we can just...
+                defer.returnValue(True)
+
+            conflict_res = [
+                self._do_power_level_conflict_res,
+                self._do_chain_length_conflict_res,
+                self._do_hash_conflict_res,
+            ]
+
+            for algo in conflict_res:
+                new_res, curr_res = algo(new_branch, current_branch)
+
+                if new_res < curr_res:
+                    defer.returnValue(False)
+                elif new_res > curr_res:
+                    defer.returnValue(True)
+
+            raise Exception("Conflict resolution failed.")
+
+        else:
+            # We need to ask for PDUs.
+            missing_prev = max(
+                new_branch[-1], current_branch[-1],
+                key=lambda x: x.depth
+            )
+
+            yield self._replication.get_pdu(
+                destination=missing_prev.origin,
+                pdu_origin=missing_prev.prev_state_origin,
+                pdu_id=missing_prev.prev_state_id,
+                outlier=True
+            )
+
+            updated_current = yield self._handle_new_state(new_pdu)
+            defer.returnValue(updated_current)
+
+    def _do_power_level_conflict_res(self, new_branch, current_branch):
+        max_power_new = max(
+            new_branch[:-1],
+            key=lambda t: t.power_level
+        ).power_level
+
+        max_power_current = max(
+            current_branch[:-1],
+            key=lambda t: t.power_level
+        ).power_level
+
+        return (max_power_new, max_power_current)
+
+    def _do_chain_length_conflict_res(self, new_branch, current_branch):
+        return (len(new_branch), len(current_branch))
+
+    def _do_hash_conflict_res(self, new_branch, current_branch):
+        new_str = "".join([p.pdu_id + p.origin for p in new_branch])
+        c_str = "".join([p.pdu_id + p.origin for p in current_branch])
+
+        return (
+            hashlib.sha1(new_str).hexdigest(),
+            hashlib.sha1(c_str).hexdigest()
+        )