ts: adopt stopper handle in poller

Author: tbg

pkg/ts/db.go

@@ -141,13 +141,18 @@ func (db *DB) PollSource(
 // start begins the goroutine for this poller, which will periodically request
 // time series data from the DataSource and store it.
 func (p *poller) start() (firstDone <-chan struct{}) {
-	ch := make(chan struct{})
-	// Poll once immediately and synchronously.
-	bgCtx := p.AnnotateCtx(context.Background())
-	if p.stopper.RunAsyncTask(bgCtx, "ts-poller", func(ctx context.Context) {
-		ch := ch // goroutine-local copy
+	ch := make(chan struct{}) // closed on completion of first poll
+	ctx, hdl, err := p.stopper.GetHandle(
+		p.AnnotateCtx(context.Background()), stop.TaskOpts{TaskName: "ts-poller"},
+	)
+	if err != nil {
+		close(ch)
+		return ch
+	}
+	go func(ctx context.Context, ch chan struct{}) {
+		defer hdl.Activate(ctx).Release(ctx)
 		var ticker timeutil.Timer
-		ticker.Reset(0)
+		ticker.Reset(0) // poll immediately
 		defer ticker.Stop()
 		for {
 			select {
@@ -162,9 +167,7 @@ func (p *poller) start() (firstDone <-chan struct{}) {
 				return
 			}
 		}
-	}) != nil {
-		close(ch)
-	}
+	}(ctx, ch)
 	return ch
 }