fix(backups): no full backup

Author: AdityaNPL

src/AgDatabase.cs

@@ -131,9 +131,19 @@ public List<BackupMetadata> RecentBackups()
     {
       // find most recent full backup LSN across all replica servers
       var fullBackupLsnBag = new ConcurrentBag<decimal>();
-      _listener.ForEachAgInstance(s => fullBackupLsnBag.Add(s.Database(Name).MostRecentFullBackupLsn()));
+      _listener.ForEachAgInstance(s => 
+      {
+        try
+        {
+          fullBackupLsnBag.Add(s.Database(Name).MostRecentFullBackupLsn());
+        }
+        catch { }
+      });
 
       // find all backups in that chain
+      if (fullBackupLsnBag.Count == 0)
+        throw new Exception("Could not find any full backups"); 
+
       var databaseBackupLsn = fullBackupLsnBag.Max();
       var bag = new ConcurrentBag<BackupMetadata>();
       _listener.ForEachAgInstance(s => s.Database(Name).BackupChainFromLsn(databaseBackupLsn)

src/SmoFacade/Database.cs

@@ -131,8 +131,13 @@ public decimal MostRecentFullBackupLsn()
       using var reader = cmd.ExecuteReader();
       if(!reader.Read())
         throw new Exception("MostRecentFullBackup SQL found no results");
+      
+      var lsnValue = reader["most_recent_full_backup_checkpoint_lsn"];
 
-      return (decimal)reader["most_recent_full_backup_checkpoint_lsn"];
+      if (lsnValue == DBNull.Value)
+        throw new Exception("MostRecentFullBackup SQL found no results");
+
+      return (decimal)lsnValue;
     }
 
     public List<BackupMetadata> BackupChainFromLsn(decimal checkpointLsn)