feat(etcdv3): support unsubscribe and subscription recovery

[leno23]

Description

Fixes #3366.

This PR fills the missing etcdv3 registry subscription lifecycle behavior:

• implements DoUnregister by deleting the registered etcd key after validating the client
• replaces the single shared config listener with per-service subscribed listeners
• implements DoUnsubscribe by closing and removing the service listener
• preserves active subscriptions when listeners are reinitialized after client restart
• dispatches data changes to every matching subscribed service key

Validation

• go test ./registry/etcdv3
• gofmt on touched files
• git diff --check

Checklist

• Code has passed local testing
• I have added tests that prove my fix is effective or that my feature works

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 53.50%. Comparing base (60d1c2a) to head (2f0c1f5).
⚠️ Report is 834 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3387      +/-   ##
===========================================
+ Coverage    46.76%   53.50%   +6.73%     
===========================================
  Files          295      493     +198     
  Lines        17172    38350   +21178     
===========================================
+ Hits          8031    20520   +12489     
- Misses        8287    16194    +7907     
- Partials       854     1636     +782     

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[leno23]

Addressed the remaining Codecov patch coverage feedback by covering the delete-event skip path and the valid-client DoUnregister path. Local validation passes: go test -coverprofile=/tmp/etcdv3.cover ./registry/etcdv3, go test ./registry/etcdv3 ./remoting/etcdv3, and git diff --check.

[Copilot]

Pull request overview

This PR fills several missing lifecycle behaviors in the etcdv3 registry to bring it closer to other registries (notably zookeeper): unregistering removes the etcd key, subscribe/unsubscribe is managed per-service (rather than via a single shared listener), and subscriptions are preserved across client restarts by reconstructing listeners during InitListeners() recovery.

Changes:

• Implement DoUnregister() by validating the etcd client and deleting the registered key.
• Refactor subscription handling to per-service listeners, adding DoUnsubscribe() that closes/removes the service listener.
• Add subscription recovery on reconnect by rebuilding listeners from previously subscribed URLs and restarting service-event watches; expand tests accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
registry/etcdv3/registry.go	Implements unregister/unsubscribe, switches to per-service subscription listeners, and adds listener recovery during re-init.
registry/etcdv3/listener.go	Reworks the data listener to dispatch to multiple subscribed listeners and adds listener close semantics/state.
registry/etcdv3/registry_test.go	Adds coverage for unregister, subscribe/unsubscribe behavior, listener close, and recovery logic.
registry/etcdv3/listener_test.go	Adds coverage for dispatch behavior, wildcard matching, unsubscribe/close behavior, and listener close/next behavior.

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[leno23]

Follow-up for the remaining Codecov partial coverage warning in registry/etcdv3/listener.go: added a focused test that drives configurationListener.Next through the skipped delete-event path when the etcd client is invalid, then verifies the next add event is returned. Local validation passes: go test ./registry/etcdv3 ./remoting/etcdv3, go test -race ./registry/etcdv3, go test -coverprofile=/tmp/etcdv3_after.out ./registry/etcdv3, and git diff --check.

[leno23]

Addressed the P1 DoUnsubscribe feedback. DoUnsubscribe now validates the event listener and the subscribed entry type before calling unsubscribeURLLocked, so error paths no longer close/remove the local subscription. I also added a regression test covering the nil event-listener path and verifying the subscription remains in the map and open. Local validation passes: go test ./registry/etcdv3 ./remoting/etcdv3, go test -race ./registry/etcdv3, go test -coverprofile=/tmp/etcdv3_fix.out ./registry/etcdv3, and git diff --check.

[leno23]

Follow-up for the failed CI lint job: changed the new error assertion to require.ErrorContains to satisfy testifylint. Local validation passes: go test ./registry/etcdv3 ./remoting/etcdv3, go test -race ./registry/etcdv3, and git diff --check. golangci-lint is not installed in this local environment, so I verified the exact reported lint issue by matching the CI log.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud