1. A method stored in one or more data-storage devices and executed using one or more processors to identify log write instructions of a source code that are potential sources of an event message of interest, the method comprising: identifying non-parametric tokens of the event message of interest read from an event-log file stored in the one or more data-storage devices; determining one or more log write instructions and associated line numbers in a source code as candidates for generating the event message of interest based on a name and version of the source code; identifying non-parametric tokens of each event message of the one or more candidate log write instructions; for each of the one or more candidate log write instructions, calculating a confidence score based the number of non-parametric tokens the event message of interest and event message of the candidate log write instruction have in common; rank ordering the one or more candidate log write instructions based on the one or more confidence scores; and displaying rank ordered candidate log write instructions, confidence scores, and associated line numbers of the source code in a graphical user interface, the confidence score of each candidate log write instruction represents a level of confidence that each log write instruction in the source code is the source of the event message of interest.