Add a default .m.rule.tombstone push rule

[turt2live]

In support of MSC1930: matrix-org/matrix-spec-proposals#1930
See also matrix-org/matrix-react-sdk#2798

[codecov]

Codecov Report

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[codecov]

Codecov Report

Merging #4867 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #4867   +/-   ##
========================================
  Coverage    59.57%   59.57%           
========================================
  Files          326      326           
  Lines        33921    33921           
  Branches      5597     5597           
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  Hits         20209    20209           
  Misses       12298    12298           
  Partials      1414     1414

[turt2live]

The MSC has cleared FCP, which means this is ready for actual review.

[erikjohnston]

This won't cause clients to be told about this new push rule down sync, but OTOH presumably we don't want to bother spending the time wiring in that update functionality now?

[turt2live]

I didn't realize this didn't push it down sync, but I also think that's fine. The set of clients which use push rules is very small, and I think they can easily create their own default if needed. Is it difficult to try and get it through sync?

[erikjohnston]

TBH I'm not sure how easy it would be to do off the top of my head. Possibly a case of adding it to the push_rules_stream table for all the users ever? That might take a while though

[turt2live]

I'll give it a try and see how badly I can break things

[turt2live]

I'm not sure how possible it is to do the background update (at least at my level). I can probably stumble my way through getting the update to work, however I don't have a good metric for progress or point of continuance when processing users.

Theory was to figure out all the users which need the push rule and call self.store.set_push_rule_enabled over the set, which causes the push_rules_stream to work and for the values to be updated in the push_rules_enabled table.

For progress I wanted to do some sort of lookup for who has push notifications enabled and who doesn't have an entry for .m.rule.tombstone in the table - the goal was to avoid updating push rules for the millions of bridge users which don't need it. However, trying to select who has the master rule disabled (because it is backwards) yields interesting results:

t2lsynapse=# select * from push_rules_enable where rule_id = 'global/override/.m.rule.master' and user_name = '@travis:t2l.io';
 id | user_name | rule_id | enabled
----+-----------+---------+---------
(0 rows)

t2lsynapse=# select count(*) from push_rules_enable where user_name = '@travis:t2l.io';
 count
-------
   593
(1 row)

I do have push notifications working though, and looking at another homeserver's database I can see that sometimes the push rule is there and sometimes not :(

So in summary: I think it's fine to expect clients to make their own defaults, or resync, or something for this rule because writing this background update looks painful. In practice I don't think there's very many clients which actually use push rules.

[richvdh]

lgtm