Implement a *fix for cron stop() before run()

Emyrk · Emyrk · commit 9b343c495784 · 2023-12-15T14:44:42.000-06:00
This fix still has a race condition. I do not see a clean solution
without modifying the cron libary. The cron library uses a boolean
to indicate running, and that boolean needs to be set to "true"
before we call "Close()". Or "Close()" should prevent "Run()"
from doing anything.

In either case, this solves the issue for a niche unit test bug
in which the test finishes, calling Close(), before there was
an oppertunity to start the go routine. It probably isn't worth
a lot of time investment, and this fix will suffice
diff --git a/agent/agentscripts/agentscripts.go b/agent/agentscripts/agentscripts.go
@@ -129,7 +129,18 @@ func (r *Runner) StartCron() {
 	// has exited by the time the `cron.Stop()` context returns, so we need to
 	// track it manually.
 	err := r.trackCommandGoroutine(func() {
-		r.cron.Run()
+		// Since this is run async, in quick unit tests, it is possible the
+		// Close() function gets called before we even start the cron.
+		// In these cases, the Run() will never end.
+		// So if we are closed, we just return, and skip the Run() entirely.
+		select {
+		case <-r.cronCtx.Done():
+		default:
+			// There is still a chance the Close() happens right here before we'
+			// r.cron.Run(). Fixing this requires modifying the cron package
+			// to add a hook for when the cron "running" flag is set.
+			r.cron.Run()
+		}
 	})
 	if err != nil {
 		r.Logger.Warn(context.Background(), "start cron failed", slog.Error(err))
