optimize CrontabWatcher

Author: yileicn

src/Infrastructure/BotSharp.Core.Crontab/Services/CrontabWatcher.cs

@@ -31,15 +31,22 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
 
             while (!stoppingToken.IsCancellationRequested)
             {
-                var isLocked = await locker.LockAsync(DIST_KEY, async () =>
+                try
                 {
-                    await RunCronChecker(scope.ServiceProvider);
-                    await Task.Delay(1000, stoppingToken);
-                });
-
-                if (!isLocked)
-                { 
-                    await Task.Delay(1000, stoppingToken);
+                    var isLocked = await locker.LockAsync(DIST_KEY, async () =>
+                    {
+                        await RunCronChecker(scope.ServiceProvider);
+                        await Task.Delay(1000, stoppingToken);
+                    });
+                    if (!isLocked)
+                    {
+                        await Task.Delay(1000, stoppingToken);
+                    }
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogWarning($"Crontab Watcher background service error: {ex.Message}");
+                    await Task.Delay(3000, stoppingToken);
                 }
             }