From b23bca73bc4368934dd846a70d2b8c0243957a37 Mon Sep 17 00:00:00 2001
From: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>
Date: Mon, 7 Jul 2025 04:54:10 +0000
Subject: [PATCH] Fix sleepWithCancel and ensure closed channel

* time.NewTicker will panic if the duration is 0. Make it return
early if duration is 0.
* Return a pre-closed channel in Wait() instead of nil. Ensures receiver
will not block forever.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>
---
 runner/pool/pool.go                   |  3 +++
 workers/cache/tool_cache.go           |  3 +++
 workers/scaleset/scaleset.go          |  8 ++++----
 workers/scaleset/scaleset_listener.go | 10 +++++++---
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/runner/pool/pool.go b/runner/pool/pool.go
index 17285e1d..9f6d3c0e 100644
--- a/runner/pool/pool.go
+++ b/runner/pool/pool.go
@@ -1369,6 +1369,9 @@ func (r *basePoolManager) deleteInstanceFromProvider(ctx context.Context, instan
 }
 
 func (r *basePoolManager) sleepWithCancel(sleepTime time.Duration) (canceled bool) {
+	if sleepTime == 0 {
+		return false
+	}
 	ticker := time.NewTicker(sleepTime)
 	defer ticker.Stop()
 
diff --git a/workers/cache/tool_cache.go b/workers/cache/tool_cache.go
index 727c82b4..6cbcc716 100644
--- a/workers/cache/tool_cache.go
+++ b/workers/cache/tool_cache.go
@@ -135,6 +135,9 @@ func (t *toolsUpdater) Reset() {
 }
 
 func (t *toolsUpdater) sleepWithCancel(sleepTime time.Duration) (canceled bool) {
+	if sleepTime == 0 {
+		return false
+	}
 	ticker := time.NewTicker(sleepTime)
 	defer ticker.Stop()
 
diff --git a/workers/scaleset/scaleset.go b/workers/scaleset/scaleset.go
index 5226d981..f5b34400 100644
--- a/workers/scaleset/scaleset.go
+++ b/workers/scaleset/scaleset.go
@@ -634,6 +634,9 @@ func (w *Worker) loop() {
 }
 
 func (w *Worker) sleepWithCancel(sleepTime time.Duration) (canceled bool) {
+	if sleepTime == 0 {
+		return false
+	}
 	ticker := time.NewTicker(sleepTime)
 	defer ticker.Stop()
 
@@ -663,10 +666,7 @@ Loop:
 			}
 			continue
 		}
-		// noop if already started. If the scaleset was just enabled, we need to
-		// start the listener here, or the <-w.listener.Wait() channel receive bellow
-		// will block forever, even if we start the listener, as a nil channel will
-		// block forever.
+		// noop if already started.
 		if err := w.listener.Start(); err != nil {
 			slog.ErrorContext(w.ctx, "error starting listener", "error", err, "consumer_id", w.consumerID)
 			if canceled := w.sleepWithCancel(2 * time.Second); canceled {
diff --git a/workers/scaleset/scaleset_listener.go b/workers/scaleset/scaleset_listener.go
index d69092f5..1274ee59 100644
--- a/workers/scaleset/scaleset_listener.go
+++ b/workers/scaleset/scaleset_listener.go
@@ -25,6 +25,10 @@ import (
 	"github.com/cloudbase/garm/util/github/scalesets"
 )
 
+var closed = make(chan struct{})
+
+func init() { close(closed) }
+
 func newListener(ctx context.Context, scaleSetHelper scaleSetHelper) *scaleSetListener {
 	return &scaleSetListener{
 		ctx:            ctx,
@@ -278,11 +282,11 @@ func (l *scaleSetListener) loop() {
 
 func (l *scaleSetListener) Wait() <-chan struct{} {
 	l.mux.Lock()
+	defer l.mux.Unlock()
+
 	if !l.running {
 		slog.DebugContext(l.ctx, "scale set listener is not running")
-		l.mux.Unlock()
-		return nil
+		return closed
 	}
-	l.mux.Unlock()
 	return l.loopExited
 }