openconfig / ygnmi / 40357820016

4%

Build Type

push

github

Committed by web-flow

Commit Message

Buffer Reconciler.errCh to prevent deadlock on subscribe error (#198)

**TLDR**: Buffer `Reconciler.errCh` with a size of 1 so `Reconciler.Start` does
not deadlock when `subscribe` returns an error.

### Problem Statement

`NewReconciler` previously initialised `errCh` as an unbuffered channel.
`Reconciler.Start` calls `subscribe` synchronously on the caller goroutine. When
`subscribe` fails, `Start` sends the error to `r.errCh` before `Start` returns.
Because the caller cannot call `Reconciler.Await` until `Start` returns, that
channel write blocked forever.

### Proposed Solution

Initialise `Reconciler.errCh` with a buffer size of 1, which matches `Watch` and
`WatchAll`. This buffer lets `Reconciler.Start` record one synchronous subscribe
error and return immediately so the caller can read the error from
`Reconciler.Await`.

### Implementation Details

- **`ygnmi/ygnmi.go`**: Initialise `errCh` with `make(chan error, 1)` in
  `NewReconciler` and document the error path in `Reconciler.Start`.
- **`internal/gnmitestutil/gnmi.go`**: Add `(*Stubber).SubscribeError` so unit
  tests can stub synchronous `Subscribe` RPC errors on `FakeGNMI`.
- **`ygnmi/ygnmi_test.go`**: Add `TestReconcileSubscribeError` to test
  `Subscribe` RPC errors, `WithUseGet`, and non-leaf `WithFT` queries with a
  1-second deadlock timeout.
- **`ygnmi/ygnmi_preferconfig_test.go`**: Regenerate the prefer-config test file
  with `go generate ./ygnmi/...`.

Coverage Stats

4 of 12 new or added lines in 2 files covered. (33.33%)

1 existing line in 1 file now uncovered.

2035 of 45260 relevant lines covered (4.5%)

0.05 hits per line