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don't store remote device lists if they have more than 10K devices

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Matthew Hodgson 2019-01-15 21:38:07 +00:00
parent 046d731fbd
commit 482d06774a
1 changed files with 13 additions and 12 deletions
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25
synapse/handlers/device.py
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@ -533,18 +533,19 @@ class DeviceListEduUpdater(object):
stream_id = result["stream_id"]
devices = result["devices"]
# Emergency hack to prevent DoS from
# @bot:oliviervandertoorn.nl and @bot:matrix-beta.igalia.com
# on Jan 15 2019: only store the most recent 1000 devices for
# a given user. (We assume we receive them in chronological
# order, which is dubious given _get_e2e_device_keys_txn does
# not explicitly order its results). Otherwise it can take
# longer than 60s to persist the >100K devices, at which point
# the internal replication request to handle the
# m.device_list_update EDU times out, causing the remote
# server to retry the transaction and thus DoS synapse master
# CPU and DB.
devices = devices[-1000:]
# If the remote server has more than ~10000 devices for this user
# we assume that something is going horribly wrong (e.g. a bot
# that logs in and creates a new device every time it tries to
# send a message). Maintaining lots of devices per user in the
# cache can cause serious performance issues as if this request
# takes more than 60s to complete, internal replication from the
# inbound federation worker to the synapse master may time out
# causing the inbound federation to fail and causing the remote
# server to retry, causing a DoS. So in this scenario we give
# up on storing the total list of devices and only handle the
# delta instead.
if len(devices) > 10000:
devices = []
yield self.store.update_remote_device_list_cache(
user_id, devices, stream_id,