Design a Logging Framework | LLD + HLD | Appenders, Async Logging, Centralized Logs

Extensible logging framework ka complete design, animation ke saath! LLD: requirements, log levels + thresholds, entities (Logger, LogEvent, Appender/transport, Layout/format, Filter, LogManager), class diagram, logger hierarchy + additivity, ek log call ka pura flow, appenders (rolling files, thread safety, Open/Closed), PatternLayout vs JSON, MDC + correlation IDs, lazy/parameterized logging, async logging (ring buffer, backpressure policies, shutdown flush), config + plugin registry + hot reload. HLD: centralized logging , scale + cost estimation, sampling, retention tiers, failures, aur Log4Shell security lesson. Note: traffic numbers are interview-style assumptions. CHAPTERS: 00:00 Design a Logging Framework 00:42 Step 1: Requirements 01:32 Log Levels and Thresholds 02:06 Step 2: Identify the Entities 02:44 Step 3: Class Diagram 03:21 Logger Hierarchy 04:10 Flow: One Log Call 04:49 Pattern: Appenders 05:37 Layouts and Structured Logging 06:17 Performance: Don't Build Strings 06:53 Async Logging 07:39 Configuration and Plugins 08:22 HLD: Centralized Logging 09:16 HLD: Scale and Cost 10:07 Failures and Security 10:49 Summary