matrix.org/static/jira/browse/SYN-582

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summary: Synapse can send many presence events causing clients to send many sync requests
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created: 2016-01-07 20:31:03.0
creator: dbkr
description: |-
Have just had Vector DoSing synapse with requests on my local setup. It looks like this is synapse's fault: the sync token is different each time and it's sending a single presence event each time for a certain user with a different last_active_ago.
Marking this P1 because this could cause the server to get hammered if hits production.
HAR log: https://matrix.org/_matrix/media/v1/download/matrix.org/iFzzljHBBXDoNuzjvPXWoxZe
id: '12280'
key: SYN-582
number: '582'
priority: '1'
project: '10000'
reporter: dbkr
resolution: '1'
resolutiondate: 2016-03-15 11:53:21.0
status: '5'
type: '1'
updated: 2016-03-15 11:53:21.0
votes: '0'
watches: '2'
workflowId: '12385'
---
actions:
- author: erikj
body: |-
What we could do is batch up presence events so we only wake up the {{/sync}} at most once every 500ms/1s (due to presence events). This would allow a bit of batching to happen.
Over what timeframe were you seeing this?
created: 2016-01-08 10:10:02.0
id: '12555'
issue: '12280'
type: comment
updateauthor: erikj
updated: 2016-01-08 10:10:02.0
- author: dbkr
body: I only let it go for 5 or 10 seconds before either refreshing the page or killing synapse. I appeared to be able to repro it fairly readily though.
created: 2016-01-08 10:12:20.0
id: '12556'
issue: '12280'
type: comment
updateauthor: dbkr
updated: 2016-01-08 10:12:20.0
- author: dbkr
body: I can only repro this with the kegan/guest_access branch of vector so it looks like this is a bug with presence and guest users.
created: 2016-01-08 11:07:16.0
id: '12557'
issue: '12280'
type: comment
updateauthor: dbkr
updated: 2016-01-08 11:07:16.0
- author: erikj
body: https://github.com/matrix-org/synapse/pull/480
created: 2016-01-12 11:22:00.0
id: '12562'
issue: '12280'
type: comment
updateauthor: erikj
updated: 2016-01-12 11:22:00.0