Request tracing. Our view of system logs as providing a control-flow perspective of system execution, when cou- pled with log messages which have unique identifiers for the relevant request or processing task, allows us to ex- tract request-flow views of the system. Much work has been done to extract request-flow views of systems, and these request flow views have then been used to diagnose and debug performance problems in distributed systems [2] [1]. However, [2] used instrumentation in the applica- tion andmiddleware to track requests and explicitlymon- itor the states that the system goes through, while [1] ex- tracted causal flows from messages in a distributed sys- tem using J2EE instrumentation developed.
