Implement per-room message retention policies

docs/sample_config.yaml

@@ -328,6 +328,69 @@ listeners:
 #
 #user_ips_max_age: 14d
 
+# 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 ##