Server Log Diagnostics (The Post-Mortem)

A bug that crashes a server leaves evidence behind. Server logs are that evidence — a timestamped, structured record of what the application was doing when it failed. This module teaches you to read logs like a detective: identify the severity level, locate the root exception, trace the call chain, and reconstruct the sequence of events that led to a failure.

You will learn the anatomy of a structured log entry (timestamp, level, thread, logger name, message, and optional stack trace), how log severity levels (TRACE through FATAL) guide your attention, and how correlation IDs allow you to follow a single request through multiple services or log files. These skills are critical for investigating intermittent production bugs that cannot be reproduced locally.

The final lesson brings everything together in the form of a post-mortem analysis. Using the 5 Whys technique, you will practice drilling past the symptom (the 500 error) to the root cause (a date parsing assumption that broke on a specific locale). You will also learn how to write a professional bug report when your only evidence is a log excerpt — a skill that separates junior testers from senior ones.