Operator panic in GetListenersServicePorts after removing default listeners

[liuz0606]

Title

v2beta1: operator panics in GetListenersServicePorts when default listeners are removed from EMQX runtime config

Body

## Bug Report

### Summary

The operator panics during reconcile when listener entries such as `listeners.ssl.default`, `listeners.ws.default`, or `listeners.wss.default` are removed from the EMQX runtime config.

The panic happens in `apis/apps/v2beta1/util.go` inside `GetListenersServicePorts()`, which assumes that each `listeners.<type>.<name>` entry is always a `hocon.Object` and performs an unsafe type assertion:

```go
obj := config.(hocon.Object)

When the runtime config returned by /api/v5/configs contains a string/scalar instead of an object for one of these listener entries, the operator crashes with:

panic: interface conversion: hocon.Value is hocon.String, not hocon.Object

Affected Versions

• emqx-operator: 2.2.25
• emqx-operator: 2.2.29
• EMQX: 5.8.4

I reproduced the same behavior on both operator versions above.

---

What I Expected

If default listeners such as 8883, 8083, and 8084 are removed or disabled, the operator should handle that gracefully and continue reconciling.

At minimum, GetListenersServicePorts() should skip invalid/non-object listener entries instead of panicking.

---

What Actually Happened

After removing default listeners from EMQX, the operator crashed during reconcile with the following stack trace:

panic: interface conversion: hocon.Value is hocon.String, not hocon.Object [recovered]
    panic: interface conversion: hocon.Value is hocon.String, not hocon.Object

goroutine 290 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
    /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.17.2/pkg/internal/controller/controller.go:116 +0x1da
panic({0x19e1200?, 0xc001bcf170?})
    /usr/local/go/src/runtime/panic.go:792 +0x132
github.com/emqx/emqx-operator/apis/apps/v2beta1.GetListenersServicePorts({0xc002782600, 0x2567})
    /workspace/apis/apps/v2beta1/util.go:268 +0x143e
github.com/emqx/emqx-operator/controllers/apps/v2beta1.generateListenerService(0xc000486c08, {0xc002782600?, 0x2567?})
    /workspace/controllers/apps/v2beta1/add_svc.go:107 +0x19b
github.com/emqx/emqx-operator/controllers/apps/v2beta1.(*addSvc).reconcile(0xc00033c1a0, {0x1efd6a8, 0xc000ba7a10}, {{0x1f01f68?, 0xc000ba7a40?}, 0xc000ba7a10?}, 0xc000486c08, {0x1eff980, 0xc000e9a4c0})
    /workspace/controllers/apps/v2beta1/add_svc.go:39 +0x385
github.com/emqx/emqx-operator/controllers/apps/v2beta1.(*EMQXReconciler).Reconcile(0xc00057aa50, {0x1efd6a8, 0xc000ba7a10}, {{{0xc00021c5a0?, 0x5?}, {0xc00021c598?, 0xc000963d10?}}})
    /workspace/controllers/apps/v2beta1/emqx_controller.go:137 +0x7a4

---

How to Reproduce

1. Deploy EMQX with emqx-operator 2.2.29 (also reproducible on 2.2.25).

2. Enable listenersServiceTemplate.

3. Configure custom listeners such as:

   • 1883
   • 2883
   • 3883

4. Remove the default listeners (ssl.default, ws.default, wss.default) from the EMQX runtime configuration, or otherwise make them disappear/change shape in /api/v5/configs.

5. Wait for the operator to reconcile.

6. The operator crashes with the panic shown above.

---

Relevant Code Path

The operator does not read listener ports directly from the EMQX CR. Instead, it fetches runtime config from:

/api/v5/configs

and then parses listeners from that returned HOCON string:

• controllers/apps/v2beta1/add_svc.go
• apis/apps/v2beta1/util.go

The problematic logic is here:

for name, config := range configs.(hocon.Object) {
    obj := config.(hocon.Object)
    cutConfig := hocon.Object{}
    if v, ok := obj["enable"]; ok {
        cutConfig["enable"] = v
    }
    if v, ok := obj["enabled"]; ok {
        cutConfig["enabled"] = v
    }
    if v, ok := obj["bind"]; ok {
        cutConfig["bind"] = v
    }
    ...
}

This assumes every listener config is always a hocon.Object, which is not true in this case.

---

Suspected Root Cause

GetListenersServicePorts() performs an unsafe type assertion:

obj := config.(hocon.Object)

If config is a hocon.String (or any non-object value), the operator panics.

This is especially easy to trigger because the operator reads from /api/v5/configs (runtime config), not directly from the Kubernetes YAML / CR spec.

---

Suggested Fix

I think there are two issues here:

1. Avoid panic in GetListenersServicePorts()

Please add a safe type check before casting:

obj, ok := config.(hocon.Object)
if !ok {
    continue
}

This would prevent the operator from crashing on unexpected listener shapes.

2. Reconsider fallback/default listener behavior in generateListenerService()

In controllers/apps/v2beta1/add_svc.go, when GetListenersServicePorts() returns no ports, the operator falls back to hardcoded defaults:

• 1883
• 8883
• 8083
• 8084

This behavior is surprising when the user intentionally removes or disables default listeners.

It may be better to:

• not inject fallback ports automatically, or
• make this behavior optional/configurable, or
• prefer listenersServiceTemplate.spec.ports when explicitly provided.

[liuz0606]

I checked the root cause in v2beta1/util.go, inside GetListenersServicePorts().

The issue is caused by an unsafe type assertion here:

obj, ok := config.(hocon.Object)
if !ok {
    continue
}

Some listener config entries are not hocon.Object, so the current logic just skips them. As a result, the corresponding listener service ports may not be parsed correctly.

A possible fix is to make the type handling more robust in GetListenersServicePorts() and avoid relying on a single concrete type when reading the listener config.

[liuz0606]

@Rory-Z @zmstone
This issue is a bug caused by an unsafe type assertion in GetListenersServicePorts().

I don't seem to have permission to edit Type or Assignees on this repository. Could a maintainer please set the issue type to bug if appropriate?

I'm also preparing a fix for this.