Always notify subscribers on membership change #6283
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Currently there is an issue: - we loose lots of updates (a separate PR to address this) - we rely on periodic (every 10s) update to update membership regardless - but it doesn't notify subscribers Because of that we were sometimes missing notifications in history and matching and didn't get any before the next rollout / restart.
dkrotx
requested review from
Shaddoll,
neil-xie,
davidporter-id-au,
Groxx,
shijiesheng,
agautam478,
jakobht,
3vilhamster,
sankari165,
taylanisikdemir and
demirkayaender
as code owners
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Otherwise we would have to time.Sleep for 10s :-(
taylanisikdemir
approved these changes
Sep 12, 2024
To cover periodic timeout update
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Currently there is an issue:
regardless
Because of that we were sometimes missing notifications in history and matching and didn't get any before the next rollout / restart.
What changed?
Subscribers of MultiringResolver were not notified if membership updated during periodic updates
Why?
Subscribers of MultiringResolver expect to be always notified on membership changes, and it doesn't really matter who triggered tag - membership update that we caught or periodic update which we do every 10s.
How did you test it?
This should just work this way, and it is been a mistake to decouple refresh/notify
Verified it on staging environments of Uber where we already see improvements during restart.
Potential risks
If some subscribers rely on event triggered the change, it can be unexpected to see an empty one (but not nil!).
At the same time, we're currently doing the same if Lookup wasn't able to find a host - we were implicitely pushing an empty changedEvent to signal the channel.
Currently existing subscriber does not rely, they simply ignore the event. In fact - it is a mistake to do the opposite: the event just triggered refresh(), but then even the refresh() builds a ring from scratch ignoring the event.
Release notes
Bugfix: Subscribers of MultiringResolver were not notified if membership updated during periodic updates