Aias00 opened a new pull request, #3516:
URL: https://github.com/apache/dubbo-go/pull/3516
## What
Two panic paths in the consistent-hash load balancer that are distinct from
the map race fixed in #3317 and the `toKey` panics fixed in #3430 / #3432.
## Why
1. **Nil selector cached.** `newSelector` returned `nil` when
`hash.arguments` contained a non-numeric index (`strconv.Atoi` failure). That
`nil` was stored in `selectors[key]`; the next `Select` for the same key
nil-dereferenced it (`selector.hashCode` at `loadbalance.go:81`, then
`selector.Select`).
```go
// selector.go (before)
i, err := strconv.Atoi(index)
if err != nil {
return nil // nil cached in selectors[key]
}
```
2. **Empty ring.** With `hash.nodes < 4`, `replicaNum/4 == 0`, so the ring
(`selector.keys`) was never populated. `selectForKey` then did `c.keys[idx]` on
an empty slice → index-out-of-range panic.
```go
// selector.go selectForKey (before)
if idx == len(c.keys) { idx = 0 }
return c.virtualInvokers[c.keys[idx]] // c.keys empty → panic
```
## Fix
- `newSelector` returns `(*selector, error)`; a bad `hash.arguments` index
surfaces as an error instead of `nil`.
- `Select` no longer caches a nil selector; on `newSelector` error it warns
and degrades to `invokers[0]`. It also nil-guards any cached selector (so a
stale nil from a prior build can't crash a later call).
- `newSelector` clamps `replicaNum` to `>= 4` so the ring is never empty.
- `selectForKey` guards `len(c.keys)==0` defensively.
## Tests
- `TestSelectDegradesOnBadHashArguments`: non-numeric `hash.arguments` no
longer panics, degrades to `invokers[0]`, and does not cache a nil selector.
- `TestSelectHandlesSmallHashNodes`: `hash.nodes=2` no longer panics.
- Updated the two existing `newSelector` call sites for the new signature.
Full `consistenthashing` package passes under `-race`.
Fixes #3510
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