|  | 1 | The nodehandler uses four different levels of logging messages: | 
          
            |  | 2 |  | 
          
            |  | 3 | * '''DEBUG''': | 
          
            |  | 4 | Those are logging messages about various internal state changes which | 
          
            |  | 5 | are mainly useful for the developers of nodehandler or for more in-depth | 
          
            |  | 6 | analysis of what's going on. They should be of little use for the casual | 
          
            |  | 7 | experimenter | 
          
            |  | 8 |  | 
          
            |  | 9 | * '''INFO''': | 
          
            |  | 10 | Those logging messages report state changes which we deemed useful to | 
          
            |  | 11 | report to the experimenter. An info message does NOT report anything | 
          
            |  | 12 | abnormal. Info messages, as the name implies inform the experimenter that | 
          
            |  | 13 | the experiment is progressing and should be considered POSITIVE feedback. | 
          
            |  | 14 |  | 
          
            |  | 15 | * '''WARNING''': | 
          
            |  | 16 | Warning messages report abnormal behavior but it is still possible | 
          
            |  | 17 | for the nodehandler to proceed. It is left to the experimenter to decide if | 
          
            |  | 18 | it makes sense to proceed or if the experiment should be stopped. Warning | 
          
            |  | 19 | messages usually originate from the nodes. There are mechanisms which would | 
          
            |  | 20 | allow an experiment script to react to those messages and potentially take | 
          
            |  | 21 | corrective actions. Right now, those mechanisms aren't fully developed and | 
          
            |  | 22 | therefore not properly documented. | 
          
            |  | 23 |  | 
          
            |  | 24 | * '''ERROR''': | 
          
            |  | 25 | Error messages report unexpected behaviors by the nodehandler or some | 
          
            |  | 26 | of its sub system. The progress of the experiment is undetermined. An error | 
          
            |  | 27 | message usually results from an unprocessed exception. | 
          
            |  | 28 |  | 
          
            |  | 29 | In short DEBUG and INFO are logging normal progress and can be ignored, WARN | 
          
            |  | 30 | and ERROR report on abnormal behavior. | 
          
            |  | 31 |  |