H
Sometimes we have variable sequences of Significant Events when we expect the certain constant number of such events in repeated normal and problem cases. For example, in repeated normal cases, we expect more than 10 events but in repeated abnormal cases - just 2 events. The latter cases would indicate that something happened inside the processing of the second event. However, if one or more such cases contain 3 or 4 events that would point to some external influence that aborted the sequence of events. We call such variable event sequences Hedges by analogy with hedge variables or variadic variables67. One of the recent examples that we encountered involved multiple abnormal cases with just 2 events. We were about to investigate the internals of the second event but noticed that one of the cases contained 3 events. Further analysis indicated that the whole sequence was aborted by some external process after reaching a certain timeout. In the case of 3 events, the first 2 happened too earlier, and that allowed for the 3rd event to happen before the timeout was triggered:
Sometimes we look at a trace or log and instead of Error Messages we only see their “signs” such as a DLL load event for an error or fault reporting module or a module that is related to symbol files such diasymreader.dll. This pattern is called by analogy to Hidden Exception68 in the memory dump analysis pattern catalog although sometimes we can see such modules in the memory dump Module Collection69. For example, the presence of diasymreader module may signify an unreported .NET exception and suggest a dump collection strategy.
The previous patterns such as Basic Facts and Vocabulary Index address the mapping of a problem description to software execution artifacts such traces and logs. Indirect Facts analysis pattern addresses the problem of incomplete problem descriptions. However, we need another pattern for completeness that addresses the mapping from a log to troubleshooting and debugging recommendations. We call it Hidden Facts that are uncovered by trace and log analysis. Of course, there can be many such hidden facts, and usually, they are uncovered after narrowing down analysis to particular Threads of Activity, Adjoint Threads, Message Context, Message Set, or Data Flow patterns. The need for that pattern had arisen during the pattern-oriented analysis of the trace case study from Malcolm McCaffery70 and can be illustrated in the following diagram:
