Logging

The application logs at four different levels DEBUG, INFO, WARNING and ERROR. In general the log messages likely to be the most interesting are the ERROR messages - and in fact in a live application you will never see the DEBUG level messages. An error message will only ever be written to the log if the generation of the exchanges was halted in any way. The error message is normally passed back to the caller of the service as described in the error sections of the Output Formats documentation.

The log file is normally found at the root of the application server and is called kidney_log.txt. This log file will grow in size over the years, if it becomes large enough that you want to remove it, it can simply be deleted. The file while then be recreated on when the algorithms are next run.

Logging Levels

DEBUG: debug messages are not written to the file as standard and will only really be useful to system developers.
INFO: info messages tend to give out progress and intermediate information, and also what operation is currently taking place. This is obviously useful when finding out where something went wrong.
WARN: warning messages are non-fatal errors. They tend to be used for problems that may indicate something is wrong but are not full blown failures.
ERROR: error messages are critical errors that have stopped the algorithm from continuing or producing a result. They generally indicate a major problem with the system, for example unexpected data formats, invalid/unknown parameters passed, unexpected system state, etc.

Example Log Files

Below is an example of what the log file might look like during a successful run of the algorithms.

     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:93]	Setting Pairwise Algorithm....
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:99]	Checking for altruistic donors....
     - Tue Dec 14 14:18:51 2010 : INFO : [ExchangeList.cpp:122]	Building data structures....
     - Tue Dec 14 14:18:51 2010 : INFO : [ExchangeList.cpp:144]	Finished building data structures....
     - Tue Dec 14 14:18:51 2010 : INFO : [ExchangeList.cpp:122]	Building data structures....
     - Tue Dec 14 14:18:51 2010 : INFO : [ExchangeList.cpp:144]	Finished building data structures....
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:106]	Finding cycles....
     - Tue Dec 14 14:18:51 2010 : INFO : [CycleCalculator.cpp:34]	Calculating two-cycles....
     - Tue Dec 14 14:18:51 2010 : INFO : [CycleCalculator.cpp:56]	Found 5 2-cycles
     - Tue Dec 14 14:18:51 2010 : INFO : [CycleCalculator.cpp:67]	Calculating three-cycles....
     - Tue Dec 14 14:18:51 2010 : INFO : [CycleCalculator.cpp:93]	Found 9 3-cycles
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:114]	Removing any altruistic cycles as required....
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:121]	Finding solution strategy....
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:129]	Running algorithm
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:131]	Finished running algorithm (LEMON) Altruistic Pairwise Exchanges
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:129]	Running algorithm
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:131]	Finished running algorithm (COIN) Optimal backarcs strategy at iteration 1
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:129]	Running algorithm
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:131]	Finished running algorithm (COIN) Optimal backarcs strategy at iteration 2
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:129]	Running algorithm
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:131]	Finished running algorithm (COIN) Optimal backarcs strategy at iteration 3
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:129]	Running algorithm
     - Tue Dec 14 14:18:51 2010 : INFO : [IPAlgorithm.cpp:131]	Finished running algorithm (COIN) Optimal set of exchanges with backarcs

The log file takes the format:

      - DATE : LEVEL : [SOURCE CODE FILE AND LINE NUMBER] MESSAGE

The info messages in the log example above give an indication of the algorithm's progress and the strategy being used by the algorithm. Also output are the total number of two-way and three-way cycles found as the algorithm is progressing.

Below we present an example of a log file containing an error message. These messages will almost certainly be unrecoverable failures, and it the case below the parsing has failed as a result of an expected element "data" not being present in the JSON input data passed to the service.

      - Tue Dec 14 11:39:22 2010 : INFO : [Parser.cpp:41]	Starting to parse file....
      - Tue Dec 14 11:39:22 2010 : ERROR : [JsonParser.cpp:38]	No data element found in the JSON passed