Message retention policies at the room and server levels

changelog.d/5815.feature

@@ -0,0 +1 @@
+Implement per-room message retention policies.

docs/sample_config.yaml

@@ -317,6 +317,69 @@ listeners:
 #
 #show_users_in_user_directory: false
 
+# Message retention policy at the server level.
+#
+# Room admins and mods can define a retention period for their rooms using the
+# 'm.room.retention' state event, and server admins can cap this period by setting
+# the 'allowed_lifetime_min' and 'allowed_lifetime_max' config options.
+#
+# If this feature is enabled, Synapse will regularly look for and purge events
+# which are older than the room's maximum retention period. Synapse will also
+# filter events received over federation so that events that should have been
+# purged are ignored and not stored again.
+#
+retention:
+  # The message retention policies feature is disabled by default. Uncomment the
+  # following line to enable it.
+  #
+  #enabled: true
+
+  # Default retention policy. If set, Synapse will apply it to rooms that lack the
+  # 'm.room.retention' state event. Currently, the value of 'min_lifetime' doesn't
+  # matter much because Synapse doesn't take it into account yet.
+  #
+  #default_policy:
+  #  min_lifetime: 1d
+  #  max_lifetime: 1y
+
+  # Retention policy limits. If set, a user won't be able to send a
+  # 'm.room.retention' event which features a 'min_lifetime' or a 'max_lifetime'
+  # that's not within this range. This is especially useful in closed federations,
+  # in which server admins can make sure every federating server applies the same
+  # rules.
+  #
+  #allowed_lifetime_min: 1d
+  #allowed_lifetime_max: 1y
+
+  # Server admins can define the settings of the background jobs purging the
+  # events which lifetime has expired under the 'purge_jobs' section.
+  #
+  # If no configuration is provided, a single job will be set up to delete expired
+  # events in every room daily.
+  #
+  # Each job's configuration defines which range of message lifetimes the job
+  # takes care of. For example, if 'shortest_max_lifetime' is '2d' and
+  # 'longest_max_lifetime' is '3d', the job will handle purging expired events in
+  # rooms whose state defines a 'max_lifetime' that's both higher than 2 days, and
+  # lower than or equal to 3 days. Both the minimum and the maximum value of a
+  # range are optional, e.g. a job with no 'shortest_max_lifetime' and a
+  # 'longest_max_lifetime' of '3d' will handle every room with a retention policy
+  # which 'max_lifetime' is lower than or equal to three days.
+  #
+  # The rationale for this per-job configuration is that some rooms might have a
+  # retention policy with a low 'max_lifetime', where history needs to be purged
+  # of outdated messages on a very frequent basis (e.g. every 5min), but not want
+  # that purge to be performed by a job that's iterating over every room it knows,
+  # which would be quite heavy on the server.
+  #
+  #purge_jobs:
+  #  - shortest_max_lifetime: 1d
+  #    longest_max_lifetime: 3d
+  #    interval: 5m:
+  #  - shortest_max_lifetime: 3d
+  #    longest_max_lifetime: 1y
+  #    interval: 24h
+
 
 ## TLS ##
 

synapse/api/constants.py

@@ -93,6 +93,8 @@ class EventTypes(object):
     ServerACL = "m.room.server_acl"
     Pinned = "m.room.pinned_events"
 
+    Retention = "m.room.retention"
+
 
 class RejectedReason(object):
     AUTH_ERROR = "auth_error"

synapse/config/server.py

@@ -228,6 +228,115 @@ def read_config(self, config):
             "show_users_in_user_directory", True,
         )
 
+        retention_config = config.get("retention")
+        if retention_config is None:
+            retention_config = {}
+
+        self.retention_enabled = retention_config.get("enabled", False)
+
+        retention_default_policy = retention_config.get("default_policy")
+
+        if retention_default_policy is not None:
+            self.retention_default_min_lifetime = retention_default_policy.get(
+                "min_lifetime"
+            )
+            if self.retention_default_min_lifetime is not None:
+                self.retention_default_min_lifetime = self.parse_duration(
+                    self.retention_default_min_lifetime
+                )
+
+            self.retention_default_max_lifetime = retention_default_policy.get(
+                "max_lifetime"
+            )
+            if self.retention_default_max_lifetime is not None:
+                self.retention_default_max_lifetime = self.parse_duration(
+                    self.retention_default_max_lifetime
+                )
+
+            if (
+                self.retention_default_min_lifetime is not None
+                and self.retention_default_max_lifetime is not None
+                and (
+                    self.retention_default_min_lifetime
+                    > self.retention_default_max_lifetime
+                )
+            ):
+                raise ConfigError(
+                    "The default retention policy's 'min_lifetime' can not be greater"
+                    " than its 'max_lifetime'"
+                )
+        else:
+            self.retention_default_min_lifetime = None
+            self.retention_default_max_lifetime = None
+
+        self.retention_allowed_lifetime_min = retention_config.get("allowed_lifetime_min")
+        if self.retention_allowed_lifetime_min is not None:
+            self.retention_allowed_lifetime_min = self.parse_duration(
+                self.retention_allowed_lifetime_min
+            )
+
+        self.retention_allowed_lifetime_max = retention_config.get("allowed_lifetime_max")
+        if self.retention_allowed_lifetime_max is not None:
+            self.retention_allowed_lifetime_max = self.parse_duration(
+                self.retention_allowed_lifetime_max
+            )
+
+        if (
+            self.retention_allowed_lifetime_min is not None
+            and self.retention_allowed_lifetime_max is not None
+            and self.retention_allowed_lifetime_min > self.retention_allowed_lifetime_max
+        ):
+            raise ConfigError(
+                "Invalid retention policy limits: 'allowed_lifetime_min' can not be"
+                " greater than 'allowed_lifetime_max'"
+            )
+
+        self.retention_purge_jobs = []
+        for purge_job_config in retention_config.get("purge_jobs", []):
+            interval_config = purge_job_config.get("interval")
+
+            if interval_config is None:
+                raise ConfigError(
+                    "A retention policy's purge jobs configuration must have the"
+                    " 'interval' key set."
+                )
+
+            interval = self.parse_duration(interval_config)
+
+            shortest_max_lifetime = purge_job_config.get("shortest_max_lifetime")
+
+            if shortest_max_lifetime is not None:
+                shortest_max_lifetime = self.parse_duration(shortest_max_lifetime)
+
+            longest_max_lifetime = purge_job_config.get("longest_max_lifetime")
+
+            if longest_max_lifetime is not None:
+                longest_max_lifetime = self.parse_duration(longest_max_lifetime)
+
+            if (
+                shortest_max_lifetime is not None
+                and longest_max_lifetime is not None
+                and shortest_max_lifetime > longest_max_lifetime
+            ):
+                raise ConfigError(
+                    "A retention policy's purge jobs configuration's"
+                    " 'shortest_max_lifetime' value can not be greater than its"
+                    " 'longest_max_lifetime' value."
+                )
+
+            self.retention_purge_jobs.append({
+                "interval": interval,
+                "shortest_max_lifetime": shortest_max_lifetime,
+                "longest_max_lifetime": longest_max_lifetime,
+            })
+
+        if not self.retention_purge_jobs:
+            self.retention_purge_jobs = [{
+                "interval": self.parse_duration("1d"),
+                "shortest_max_lifetime": None,
+                "longest_max_lifetime": None,
+            }]
+
         self.listeners = []
         for listener in config.get("listeners", []):
             if not isinstance(listener.get("port", None), int):
@@ -666,6 +775,69 @@ def default_config(self, server_name, data_dir_path, **kwargs):
         # 'true'.
         #
         #show_users_in_user_directory: false
+
+        # Message retention policy at the server level.
+        #
+        # Room admins and mods can define a retention period for their rooms using the
+        # 'm.room.retention' state event, and server admins can cap this period by setting
+        # the 'allowed_lifetime_min' and 'allowed_lifetime_max' config options.
+        #
+        # If this feature is enabled, Synapse will regularly look for and purge events
+        # which are older than the room's maximum retention period. Synapse will also
+        # filter events received over federation so that events that should have been
+        # purged are ignored and not stored again.
+        #
+        retention:
+          # The message retention policies feature is disabled by default. Uncomment the
+          # following line to enable it.
+          #
+          #enabled: true
+
+          # Default retention policy. If set, Synapse will apply it to rooms that lack the
+          # 'm.room.retention' state event. Currently, the value of 'min_lifetime' doesn't
+          # matter much because Synapse doesn't take it into account yet.
+          #
+          #default_policy:
+          #  min_lifetime: 1d
+          #  max_lifetime: 1y
+
+          # Retention policy limits. If set, a user won't be able to send a
+          # 'm.room.retention' event which features a 'min_lifetime' or a 'max_lifetime'
+          # that's not within this range. This is especially useful in closed federations,
+          # in which server admins can make sure every federating server applies the same
+          # rules.
+          #
+          #allowed_lifetime_min: 1d
+          #allowed_lifetime_max: 1y
+
+          # Server admins can define the settings of the background jobs purging the
+          # events which lifetime has expired under the 'purge_jobs' section.
+          #
+          # If no configuration is provided, a single job will be set up to delete expired
+          # events in every room daily.
+          #
+          # Each job's configuration defines which range of message lifetimes the job
+          # takes care of. For example, if 'shortest_max_lifetime' is '2d' and
+          # 'longest_max_lifetime' is '3d', the job will handle purging expired events in
+          # rooms whose state defines a 'max_lifetime' that's both higher than 2 days, and
+          # lower than or equal to 3 days. Both the minimum and the maximum value of a
+          # range are optional, e.g. a job with no 'shortest_max_lifetime' and a
+          # 'longest_max_lifetime' of '3d' will handle every room with a retention policy
+          # which 'max_lifetime' is lower than or equal to three days.
+          #
+          # The rationale for this per-job configuration is that some rooms might have a
+          # retention policy with a low 'max_lifetime', where history needs to be purged
+          # of outdated messages on a very frequent basis (e.g. every 5min), but not want
+          # that purge to be performed by a job that's iterating over every room it knows,
+          # which would be quite heavy on the server.
+          #
+          #purge_jobs:
+          #  - shortest_max_lifetime: 1d
+          #    longest_max_lifetime: 3d
+          #    interval: 5m:
+          #  - shortest_max_lifetime: 3d
+          #    longest_max_lifetime: 1y
+          #    interval: 24h
         """ % locals()
 
     def read_arguments(self, args):

synapse/events/validator.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from six import string_types
+from six import integer_types, string_types
 
 from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes, Membership
 from synapse.api.errors import Codes, SynapseError
@@ -22,11 +22,12 @@
 
 
 class EventValidator(object):
-    def validate_new(self, event):
+    def validate_new(self, event, config):
         """Validates the event has roughly the right format
 
         Args:
-            event (FrozenEvent)
+            event (FrozenEvent): The event to validate.
+            config (Config): The homeserver's configuration.
         """
         self.validate_builder(event)
 
@@ -67,6 +68,99 @@ def validate_new(self, event):
                             Codes.INVALID_PARAM,
                         )
 
+        if event.type == EventTypes.Retention:
+            self._validate_retention(event, config)
+
+    def _validate_retention(self, event, config):
+        """Checks that an event that defines the retention policy for a room respects the
+        boundaries imposed by the server's administrator.
+
+        Args:
+            event (FrozenEvent): The event to validate.
+            config (Config): The homeserver's configuration.
+        """
+        min_lifetime = event.content.get("min_lifetime")
+        max_lifetime = event.content.get("max_lifetime")
+
+        if min_lifetime is not None:
+            if not isinstance(min_lifetime, integer_types):
+                raise SynapseError(
+                    code=400,
+                    msg="'min_lifetime' must be an integer",
+                    errcode=Codes.BAD_JSON,
+                )
+
+            if (
+                config.retention_allowed_lifetime_min is not None
+                and min_lifetime < config.retention_allowed_lifetime_min
+            ):
+                raise SynapseError(
+                    code=400,
+                    msg=(
+                        "'min_lifetime' can't be lower than the minimum allowed"
+                        " value enforced by the server's administrator"
+                    ),
+                    errcode=Codes.BAD_JSON,
+                )
+
+            if (
+                config.retention_allowed_lifetime_max is not None
+                and min_lifetime > config.retention_allowed_lifetime_max
+            ):
+                raise SynapseError(
+                    code=400,
+                    msg=(
+                        "'min_lifetime' can't be greater than the maximum allowed"
+                        " value enforced by the server's administrator"
+                    ),
+                    errcode=Codes.BAD_JSON,
+                )
+
+        if max_lifetime is not None:
+            if not isinstance(max_lifetime, integer_types):
+                raise SynapseError(
+                    code=400,
+                    msg="'max_lifetime' must be an integer",
+                    errcode=Codes.BAD_JSON,
+                )
+
+            if (
+                config.retention_allowed_lifetime_min is not None
+                and max_lifetime < config.retention_allowed_lifetime_min
+            ):
+                raise SynapseError(
+                    code=400,
+                    msg=(
+                        "'max_lifetime' can't be lower than the minimum allowed value"
+                        " enforced by the server's administrator"
+                    ),
+                    errcode=Codes.BAD_JSON,
+                )
+
+            if (
+                config.retention_allowed_lifetime_max is not None
+                and max_lifetime > config.retention_allowed_lifetime_max
+            ):
+                raise SynapseError(
+                    code=400,
+                    msg=(
+                        "'max_lifetime' can't be greater than the maximum allowed"
+                        " value enforced by the server's administrator"
+                    ),
+                    errcode=Codes.BAD_JSON,
+                )
+
+        if (
+            min_lifetime is not None
+            and max_lifetime is not None
+            and min_lifetime > max_lifetime
+        ):
+            raise SynapseError(
+                code=400,
+                msg="'min_lifetime' can't be greater than 'max_lifetime",
+                errcode=Codes.BAD_JSON,
+            )
+
     def validate_builder(self, event):
         """Validates that the builder/event has roughly the right format. Only
         checks values that we expect a proto event to have, rather than all the