Lcos-000 commented on code in PR #3623:
URL: https://github.com/apache/dubbo-go/pull/3623#discussion_r3750116665
##########
registry/servicediscovery/service_discovery_registry.go:
##########
@@ -514,11 +514,10 @@ func (s *serviceDiscoveryRegistry) Subscribe(url
*common.URL, notify registry.No
" either specify 'provided-by' for reference or enable
metadata-report center subscription url:%s", url.String())
} else {
logger.Infof("[Registry][ServiceDiscovery] find initial mapping
applications %q for service %s", services, url.ServiceKey())
- // first notify
- err :=
mappingListener.OnEvent(registry.NewServiceMappingChangedEvent(url.ServiceKey(),
services))
- if err != nil {
- logger.Errorf("[Registry][ServiceDiscovery]
ServiceInstancesChangedListenerImpl handle error, err=%v", err)
- }
+ // Subscribe the initial applications directly. The mapping
listener tracks
+ // changes after the initial subscription; routing this event
through it
+ // makes provided-by look like an unchanged mapping and skips
SubscribeURL.
+ s.SubscribeURL(url, notify, services)
Review Comment:
Thanks for the P1 and the repro — confirmed. `SubscribeURL`'s fast path
still calls `subscribeAndNotify`, which spawns `go
s.serviceDiscovery.AddListener(listener)` unconditionally, so a same-set replay
on the metadata-report path re-registers (AddListener 1->2 in your test).
Narrowed the fix in commit `ed4176d1`:
- `provided-by` path: subscribe directly via `SubscribeURL` (explicit,
unchanging target — no diff semantics apply)
- metadata-report path: keep the initial subscription on `OnEvent` so
`oldServiceNames` baseline is updated and later A->A is a no-op
Added regression coverage:
- `TestServiceDiscoveryRegistrySubscribeMetadataReportA2A`: initial
subscribe + replay identical mapping -> `AddListener` stays at 1
- `TestServiceDiscoveryRegistrySubscribeWithProvidedBy`: `AddListener` fires
exactly once, `GetInstances(test-app)` invoked
`go test ./registry/servicediscovery/` passes.
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