Logger Framework — Notes

Functional

• Hierarchical loggers (com.foo.bar).
• Levels per logger.
• Multiple appenders + formatters.
• Filters.
• MDC / structured fields.
• Async + sync delivery.

Non-functional

• Sub-µs hot path when level disabled.
• No log loss under burst (lossless async + bounded queue).
• No deadlocks (re-entrant logging).

Trade-offs

• Sync is simple but blocks on slow appender; async decouples but loses on crash unless flushed.
• JSON vs text: JSON wins for aggregation; text wins for greppable local files.
• Per-thread context (MDC) invaluable for request tracing.

Refs

• Log4j 2, Logback, SLF4J architecture docs.
• "Logger frameworks comparison" articles.