Derive all internal contexts from Client context

We were previously using `context.Background()` in some situations to
avoid cancellation of things that really shouldn't be cancelled by the
user context cancellation. However, we can now do that with
`context.WithoutCancel` instead in order to preserve context values
without any cancellation or deadline.

Fixes #512.

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Derive all internal contexts from user-provided `Client` context. This includes the job fetch context, notifier unlisten, and completer. [PR #514](https://github.com/riverqueue/river/pull/514).
+
 ## [0.11.1] - 2024-08-05
 
 ### Fixed

internal/jobcompleter/job_completer.go

@@ -506,7 +506,7 @@ func (c *BatchCompleter) waitOrInitBacklogChannel(ctx context.Context) {
 const numRetries = 3
 
 func withRetries[T any](logCtx context.Context, baseService *baseservice.BaseService, disableSleep bool, retryFunc func(ctx context.Context) (T, error)) (T, error) {
-	uncancelledCtx := context.Background()
+	uncancelledCtx := context.WithoutCancel(logCtx)
 
 	var (
 		defaultVal T

internal/notifier/notifier.go

@@ -35,8 +35,8 @@ type Subscription struct {
 
 func (s *Subscription) Unlisten(ctx context.Context) {
 	s.unlistenOnce.Do(func() {
-		// Unlisten uses background context in case of cancellation.
-		if err := s.notifier.unlisten(context.Background(), s); err != nil { //nolint:contextcheck
+		// Unlisten strips cancellation from the parent context to ensure it runs:
+		if err := s.notifier.unlisten(context.WithoutCancel(ctx), s); err != nil { //nolint:contextcheck
 			s.notifier.Logger.ErrorContext(ctx, s.notifier.Name+": Error unlistening on topic", "err", err, "topic", s.topic)
 		}
 	})

producer.go

@@ -459,7 +459,7 @@ func (p *producer) fetchAndRunLoop(fetchCtx, workCtx context.Context, fetchLimit
 
 func (p *producer) innerFetchLoop(workCtx context.Context, fetchResultCh chan producerFetchResult) {
 	limit := p.maxJobsToFetch()
-	go p.dispatchWork(limit, fetchResultCh) //nolint:contextcheck
+	go p.dispatchWork(workCtx, limit, fetchResultCh)
 
 	for {
 		select {
@@ -509,14 +509,15 @@ func (p *producer) maybeCancelJob(id int64) {
 	executor.Cancel()
 }
 
-func (p *producer) dispatchWork(count int, fetchResultCh chan<- producerFetchResult) {
-	// This intentionally uses a background context because we don't want it to
-	// get cancelled if the producer is asked to shut down. In that situation, we
-	// want to finish fetching any jobs we are in the midst of fetching, work
-	// them, and then stop. Otherwise we'd have a risk of shutting down when we
-	// had already fetched jobs in the database, leaving those jobs stranded. We'd
-	// then potentially have to release them back to the queue.
-	jobs, err := p.exec.JobGetAvailable(context.Background(), &riverdriver.JobGetAvailableParams{
+func (p *producer) dispatchWork(workCtx context.Context, count int, fetchResultCh chan<- producerFetchResult) {
+	// This intentionally removes any deadlines or cancelleation from the parent
+	// context because we don't want it to get cancelled if the producer is asked
+	// to shut down. In that situation, we want to finish fetching any jobs we are
+	// in the midst of fetching, work them, and then stop. Otherwise we'd have a
+	// risk of shutting down when we had already fetched jobs in the database,
+	// leaving those jobs stranded. We'd then potentially have to release them
+	// back to the queue.
+	jobs, err := p.exec.JobGetAvailable(context.WithoutCancel(workCtx), &riverdriver.JobGetAvailableParams{
 		AttemptedBy: p.config.ClientID,
 		Max:         count,
 		Queue:       p.config.Queue,