don't store more remote device lists if they have more than 1K devices (#4397)

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Richard van der Hoff 2019-01-16 23:14:11 +00:00 committed by GitHub
parent 7f1a6a4ea5
commit 05e1296649
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changelog.d/4397.bugfix Normal file
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@ -0,0 +1 @@
Fix high CPU usage due to remote devicelist updates

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@ -532,6 +532,25 @@ class DeviceListEduUpdater(object):
stream_id = result["stream_id"]
devices = result["devices"]
# If the remote server has more than ~1000 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) > 1000:
logger.warn(
"Ignoring device list snapshot for %s as it has >1K devs (%d)",
user_id, len(devices)
)
devices = []
yield self.store.update_remote_device_list_cache(
user_id, devices, stream_id,
)