diff --git a/synapse/config/retention.py b/synapse/config/retention.py
new file mode 100644
index 0000000000..aed9bf458f
--- /dev/null
+++ b/synapse/config/retention.py
@@ -0,0 +1,226 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+import logging
+from typing import List, Optional
+
+import attr
+
+from synapse.config._base import Config, ConfigError
+
+logger = logging.getLogger(__name__)
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class RetentionPurgeJob:
+ """Object describing the configuration of the manhole"""
+
+ interval: int
+ shortest_max_lifetime: Optional[int]
+ longest_max_lifetime: Optional[int]
+
+
+class RetentionConfig(Config):
+ section = "retention"
+
+ def read_config(self, config, **kwargs):
+ 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
+
+ if self.retention_enabled:
+ logger.info(
+ "Message retention policies support enabled with the following default"
+ " policy: min_lifetime = %s ; max_lifetime = %s",
+ self.retention_default_min_lifetime,
+ self.retention_default_max_lifetime,
+ )
+
+ 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: List[RetentionPurgeJob] = []
+ 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(
+ RetentionPurgeJob(interval, shortest_max_lifetime, longest_max_lifetime)
+ )
+
+ if not self.retention_purge_jobs:
+ self.retention_purge_jobs = [
+ RetentionPurgeJob(self.parse_duration("1d"), None, None)
+ ]
+
+ def generate_config_section(self, config_dir_path, server_name, **kwargs):
+ return """\
+ # 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, and the state of a room contains a
+ # 'm.room.retention' event in its state which contains a 'min_lifetime' or a
+ # 'max_lifetime' that's out of these bounds, Synapse will cap the room's policy
+ # to these limits when running purge jobs.
+ #
+ #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 more frequent basis than for the rest of the rooms
+ # (e.g. every 12h), but not want that purge to be performed by a job that's
+ # iterating over every room it knows, which could be heavy on the server.
+ #
+ # If any purge job is configured, it is strongly recommended to have at least
+ # a single job with neither 'shortest_max_lifetime' nor 'longest_max_lifetime'
+ # set, or one job without 'shortest_max_lifetime' and one job without
+ # 'longest_max_lifetime' set. Otherwise some rooms might be ignored, even if
+ # 'allowed_lifetime_min' and 'allowed_lifetime_max' are set, because capping a
+ # room's policy to these values is done after the policies are retrieved from
+ # Synapse's database (which is done using the range specified in a purge job's
+ # configuration).
+ #
+ #purge_jobs:
+ # - longest_max_lifetime: 3d
+ # interval: 12h
+ # - shortest_max_lifetime: 3d
+ # interval: 1d
+ """
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