etcd-io
[release-3.5] server: cleanup zombie membership information
There are three places where zombie membership information can be cleaned up:
1. ApplierV2 -> UpdateAttributes
Ideally, each member updates its own attributes only once before serving
requests. Since this happens only at startup and at low frequency, it is
safe to clean up zombie members during this operation.
Additionally, pending logs are always applied before attributes are updated,
so there is no data race.
2. Applying a snapshot via Raft message
When a member receives a snapshot through a Raft message, the v2store is
synchronized with the v3store. This makes it safe to detect and clean up
zombie membership entries at that time.
3. Applying ConfChange
Check and cleanup zombie members after ConfChange. Ideally, there aren't
too many ConfChange, the impact on performance should be minimal.
Fixes: #20967
Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.
@ahrtr for this comment,
As mentioned above, I am thinking probably we should handle the case missing members in v3store (exist in v2, but not in v3) as well, although we haven't seen any reproduction for such case so far.
I think we can keep it as it is right now. based on current situation, v3store has more information than v2store. If we don't have such case like v2store contains more information than v3, we can assume it's not going to happen.
If we don't have such case like v2store contains more information than v3, we can assume it's not going to happen.
Hopefully we won't have to fix a follow-up issue and generate a follow-up blog.
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This pull-request has been approved by: ahrtr, fuweid
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