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Posted to notifications@dubbo.apache.org by "AsperforMias (via GitHub)" <gi...@apache.org> on 2026/07/08 14:49:44 UTC
[I] [BUG] Polaris interface registry may keep stale providers after initial load [dubbo-go]
AsperforMias opened a new issue, #3480:
URL: https://github.com/apache/dubbo-go/issues/3480
## 👋 Thank you for your feedback!
This issue tracks a potential stale provider problem in the Polaris interface-level registry path, similar to the Nacos initial subscribe snapshot issue fixed by #3479.
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## 🔧 Environment Information
### 🚀 Go Version
1.23+
### 📦 Dubbo-go Version
main branch after #3479 / affected versions likely include releases with the current Polaris interface-level registry implementation.
### 🖥️ Server Configuration
Dubbo-go or Dubbo provider using interface-level registry.
### 💻 Client Configuration
Dubbo-go consumer using the Polaris registry implementation.
### 🌐 Protocol Configuration
Any Dubbo-go protocol using interface-level registry discovery.
### 📋 Registry Configuration
Polaris registry, interface-level registry path (`registry/polaris`), not application-level service discovery.
### 💾 Operating System
🐧 Linux
---
## 🐛 Issue Details
### 📝 Bug Description
`polarisRegistry.LoadSubscribeInstances` synchronously loads the initial provider instances and notifies the directory with per-instance `ADD` events. Later, `polarisRegistry.Subscribe` starts a Polaris watcher. The watcher sends the initial `WatchService` full instance list as `EventTypeAdd` events for each current instance.
If an instance is returned by `LoadSubscribeInstances` but disappears before `WatchService` is established, the directory has already cached an invoker for the old instance. The watcher only emits `ADD` events for the current list and does not generate a `DEL` for the instance that disappeared between the synchronous load and the watcher startup. As a result, the stale invoker can remain in the directory cache.
Relevant code:
- `registry/polaris/registry.go`: `LoadSubscribeInstances` calls `GetInstances` and notifies each instance as `EventTypeAdd`.
- `registry/polaris/core.go`: `startWatch` sends `resp.GetAllInstancesResp.Instances` as `EventTypeAdd`.
- `registry/polaris/listener.go`: the listener forwards each instance as an incremental `Notify` event.
- `registry/directory/directory.go`: incremental `ADD` is idempotent for existing keys but does not remove old keys; stale entries require an explicit `DEL` or a full-list `NotifyAll` refresh.
### 🔄 Steps to Reproduce
1. Configure a Dubbo-go consumer to use the Polaris interface-level registry implementation.
2. Start with provider instance A registered in Polaris.
3. During consumer startup, let `LoadSubscribeInstances` load A and notify the directory with `ADD(A)`.
4. Before the Polaris watcher finishes `WatchService` initialization, replace A with provider instance B, or remove A.
5. The watcher initial response contains only the current instance list, for example B or empty.
6. The watcher emits `ADD(B)` or no event for A, but no `DEL(A)` is emitted.
7. The directory may keep the stale invoker for A.
### ✅ Expected Behavior
Instances loaded by `LoadSubscribeInstances` should be reconciled with the first Polaris watcher snapshot. If an initially loaded instance is absent from the first watcher result, Dubbo-go should remove it from the directory cache, either by emitting a `DEL` event or by applying a full-list refresh semantics.
### ❌ Actual Behavior
The initial synchronous load and the watcher path are not reconciled. The watcher initial snapshot is treated as incremental `ADD` events only. Providers that were added by `LoadSubscribeInstances` but are absent from the first watcher snapshot may remain as stale invokers.
### 💡 Possible Solution
Apply a similar reconciliation strategy to the Nacos fix in #3479, or change Polaris watcher initial snapshot handling to full-list semantics:
1. Keep the `LoadSubscribeInstances` result as an initial snapshot baseline and seed the Polaris listener/watcher before processing the first watcher response, so missing instances can produce `DEL` events.
2. Alternatively, treat the first `WatchService` full instance list as a complete refresh and notify the directory via `NotifyAll`, allowing it to remove cached invokers not present in the current list.
The implementation should be limited to the Polaris interface-level registry path and should not affect the application-level service discovery path, which already uses full-list `NotifyAll` refresh semantics.
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Re: [I] [BUG] Polaris interface registry may keep stale providers after initial load [dubbo-go]
Posted by "Vanillaxi (via GitHub)" <gi...@apache.org>.
Vanillaxi commented on issue #3480:
URL: https://github.com/apache/dubbo-go/issues/3480#issuecomment-4916076784
Can I have a try
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Re: [I] [BUG] Polaris interface registry may keep stale providers after initial load [dubbo-go]
Posted by "Alanxtl (via GitHub)" <gi...@apache.org>.
Alanxtl closed issue #3480: [BUG] Polaris interface registry may keep stale providers after initial load
URL: https://github.com/apache/dubbo-go/issues/3480
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Re: [I] [BUG] Polaris interface registry may keep stale providers after initial load [dubbo-go]
Posted by "Alanxtl (via GitHub)" <gi...@apache.org>.
Alanxtl commented on issue #3480:
URL: https://github.com/apache/dubbo-go/issues/3480#issuecomment-5086356795
close via #3482
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