spring-boot-logging

Spring Boot Logging Engine

Rules

• Use @Slf4j for logger declaration in every class that emits log events.
• Use *LogMessages components to resolve all log message strings through i18n keys.
• Pass the resolved string as the sole argument to the log.LEVEL() call.
• Add the request correlation identifier to MDC under the key traceId before processing begins.
• Clear traceId from MDC after request processing completes.
• Include correlation identifiers when available in log statements.
• Log events with clear operational value.
• Use consistent level semantics across features.
• Use DEBUG level for development-time diagnostic events that have no operational value in production.
• In controller classes, log only warning and error conditions.
• In service classes, log business state transitions (create, update, delete) at INFO level with stable resource identifiers.
• In repository classes, log degraded execution paths (for example, SQL feature fallback) at WARN level.
• Log unexpected exceptions at ERROR level.
• Log known domain failures that map to 4xx responses at WARN level.
• Keep exception logs single-source to avoid duplication.
• Use parameterized log messages instead of string concatenation.
• Use structured log fields when the active logging sink supports structured ingestion.
• Place logback-spring.xml under src/main/resources/log/ to align with the classpath:log/logback-spring.xml reference declared in application.yml.
• Source application name from spring.application.name into context variable APPLICATION_NAME.
• Source log directory from logging.file.path into context variable LOG_DIR with defaultValue="./logs".
• Configure a Console appender with encoder pattern: %black(%d{ISO8601}) %highlight(%-5level) [%blue(%t)] %yellow(%logger{60}): %msg%n%throwable
• Configure a RollingFile appender with encoder pattern: %d{ISO8601} %-5level [%t] %logger{60}: %msg%n%throwable
• Set the active log file path in the RollingFile appender: <file>${LOG_DIR}/${APPLICATION_NAME}.log</file>.
• Set SizeAndTimeBasedRollingPolicy on the RollingFile appender with archived file pattern: ${LOG_DIR}/archived/${APPLICATION_NAME}-%d{yyyy-MM-dd}.%i.gz
• Set rotation limits: maxFileSize=10MB, maxHistory=7, totalSizeCap=1GB.
• Declare all rotation limits explicitly in the rolling policy.
• Route the RollingFile appender through an async appender named File.
• Declare elements in this order within the async appender: queueSize, discardingThreshold, appender-ref.
• Set queueSize=512 and discardingThreshold=0 on the async appender.
• Route the debug profile to Console and File appenders with root level DEBUG.
• Route the development profile to Console and File appenders with root level INFO.
• Route the default | production profiles to the File appender only with root level INFO.
• Use structured encoders when the log aggregation sink requires structured ingestion.