hyperledger / fabric-x-committer / 30747708169

91%

main: 91%

Build Type

Pull #726

github

Committed by liran-funaro

Commit Message

[utils] Distinguish an optional channel output from a failed write

#### Type of change

- Bug fix
- Improvement (improvement to code, performance, etc)
- Test update

#### Description

- Add `channel.NewOptionalWriter`, for an output the caller may leave unset. When its output is
  nil the value is discarded and the write reports success, so writing unconditionally does not
  look like a delivery failure.
- `channel.NewWriter` keeps its contract: a nil output always reports failure, since the value
  cannot be delivered. Documented on the constructor, along with which one to reach for.
- Use the new constructor in `utils/deliver` and `utils/deliverorderer`, the two places that treat
  a nil output channel as "this output is not wanted", and correct their comments. They claimed
  the write was a no-op while it was in fact reported as failed; both discard the result, so
  neither was affected.
- Document on `deliver.Parameters` that its two output channels are optional. `deliverorderer`
  already documents this on its own parameters.

#### Additional details (Optional)

The distinction matters because a `false` return is what tells a caller its value was not
delivered, and several callers use it to decide whether to return in-flight work to a tracker and
retry — for example the coordinator's VC manager, which re-adds a batch to `txBeingValidated` when
a forward fails. Making a nil output report success globally would turn a misconfigured output
into silent data loss, so the discarding behavior is opt-in per writer rather than the default.

`TestNilOutputWriter` covers the four cases: a nil required output, a nil optional output, an
optional output that is set (which must behave exactly like `NewWriter`, including on
cancellation), and an optional writer passed through `WithContext`.

#### Related issues

- resolves #722

Signed-off-by: Liran Funaro <liran.funaro@gmail.com>

Pull Request Pull Request #726: [utils] Distinguish an optional channel output from a failed write

Coverage Stats

29 of 29 new or added lines in 3 files covered. (100.0%)

16 existing lines in 6 files now uncovered.

10595 of 11587 relevant lines covered (91.44%)

37807.29 hits per line