Extremities dummy event came down sync

[anoadragon453]

Description

I received a org.matrix.dummy_event down sync which isn't supposed to happen.

{
    "type": "org.matrix.dummy_event",
    "sender": "@andrewm:amorgan.xyz",
    "content": {},
    "event_id": "$15704495153065cWESB:amorgan.xyz",
    "origin_server_ts": 1570449515558,
    "unsigned": {
        "age": 2338
    },
    "room_id": "!UwfyezyoefyCIPOOXS:matrix.org"
}

Not seeing anything in the homeserver logs about it.

Version information

• Homeserver: amorgan.xyz

If not matrix.org:

• Version: v1.4.0

• Install method: pip

• Platform: debian stretch

[richvdh]

isn't it? I thought this was expected. I see them all the time.

[anoadragon453]

@erikjohnston claims otherwise

[benparsons]

Is https://github.com/matrix-org/synapse/blob/master/synapse/handlers/message.py#L901 the only use-case for these events?

Would be good to create a document explaining these events because I've just started seeing them from my own server (which is weird to witness) and couldn't find anything else.

[babolivier]

It looks like a simple enough fix would just be to filter them out in filter_events_for_client.

isn't it? I thought this was expected. I see them all the time.

imho it results in a pretty crappy UX since it means events from X weeks ago can appear randomly in the middle of a convo happening today and "split" the timeline.

[babolivier]

Fixed in #7035