Maxkit: SpringBoot3 - Spring Boot Log

spring 提供的 Logging :: Spring Boot 有以下幾種

name	package
Java Util Logging	spring-boot-starter-logging
Logback	spring-boot-starter-logging
Log4j2	spring-boot-starter-log4j2

spring-boot-starter-logging 是預設引用的，所有 spring-boot-starter-* 都會引用 spring-boot-starter-logging。不需要自行引用。

spring-boot-starter-logging 使用 Commons Logging，支援 Java Util Logging、Log4j2、Logback

使用 starter 預設會使用 Logback，透過 logback 支援 Java Util Logging, Commons Logging, Log4J, or SLF4J。

Log Format

2024-11-15T17:25:40.765+08:00  INFO 4924 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port 8080 (http)

Date & Time
Log Level
Process ID
--- separator
[Application name] 如果有設定 spring.application.name 才會出現
[Thread name]
Correlation ID 如果有設定 tracing 才會出現
Logger name 通常是來源 class name 的縮寫
log message

Console Output

預設會出現 ERROR-level, WARN-level, and INFO-level messages

如果在 CLI 有加上 java -jar Demo1.jar --debug debug flag，就會出現 core loggers (embedded container, Hibernate, and Spring Boot) 更多的資訊。這邊不代表 application 的 DEBUG level message 會出現

CLI 也可以加上 --trace ，會增加 core logger 資訊

Color-coded Output

terminal 有支援 ANSI 時，就可以增加顏色

ex: %clr(%5p)

Level	Color
`FATAL`	Red
`ERROR`	Red
`WARN`	Yellow
`INFO`	Green
`DEBUG`	Green
`TRACE`	Green

可以自訂顏色

blue
cyan
faint
green
magenta
red
yellow

ex: %clr(%d{yyyy-MM-dd'T'HH:mm:ss.SSSXXX}){yellow}

File Output

spring boot 預設只會寫入 console log

要寫入 file log 必須設定 logging.file.name 或 logging.file.path，兩個都設定時，只會使用 logging.file.name。log file rotate 預設為 10M，log level 跟 console 一樣，會寫入 ERROR, WARN, INFO level

File Rotation

調整 log rotate 規則

要修改 application.properties(yaml)，如果是 log4j 就要設定 log4j2.xml or log4j2-spring.xml

name	desc
logging.logback.rollingpolicy.file-name-pattern	filename pattern
logging.logback.rollingpolicy.clean-history-on-start	在 application 啟動時，要做 log cleanup
logging.logback.rollingpolicy.max-file-size	logfile 的最大 size
logging.logback.rollingpolicy.total-size-cap	log archives 刪除前的最大 size
logging.logback.rollingpolicy.max-history	archive log files 保留幾個(default: 7)

Log Level

logging.level.<logger-name>=<level>

為 TRACE, DEBUG, INFO, WARN, ERROR, FATAL, or OFF 其中一個

logging.level.root 是設定 root logger

logging:
  level:
    root: "warn"
    org.springframework.web: "debug"
    org.hibernate: "error"

也可以設定環境變數，ex:

LOGGING_LEVEL_ORG_SPRINGFRAMEWORK_WEB=DEBUG

Log Groups

ex: 一次設定所有 tomcat 相關的 logger level，group 合併後，再設定 level

在 applicaiton.yaml

logging:
  group:
    tomcat: "org.apache.catalina,org.apache.coyote,org.apache.tomcat"

logging:
  level:
    tomcat: "trace"

spring pre-defined logging groups

name	loggers
web	org.springframework.core.codec, org.springframework.http, org.springframework.web, org.springframework.boot.actuate.endpoint.web, org.springframework.boot.web.servlet.ServletContextInitializerBeans
sql	org.springframework.jdbc.core, org.hibernate.SQL, org.jooq.tools.LoggerListener

Log Shutdown hook

要在 application 關閉前，release logging resource，要在 JVM exits 時，加上 shutdown hook

使用 jar 時，shutdown hook 會自動註冊

如要關閉 shutdown hook

logging:
  register-shutdown-hook: false

Custom Log Configuration

logging.config 決定 logging framework，然後就能使用該 framework 的設定檔

Logging System	Customization
Logback	`logback-spring.xml`, `logback-spring.groovy`, `logback.xml`, or `logback.groovy`
Log4j2	`log4j2-spring.xml` or `log4j2.xml`
JDK (Java Util Logging)	`logging.properties`

建議使用 logback-spring.xml，不要用 logback.xml，spring 可能會無法控制 log 初始化

以下設定參數，可轉換為環境變數

Spring Environment	System Property	Comments
`logging.exception-conversion-word`	`LOG_EXCEPTION_CONVERSION_WORD`	The conversion word used when logging exceptions.
`logging.file.name`	`LOG_FILE`	If defined, it is used in the default log configuration.
`logging.file.path`	`LOG_PATH`	If defined, it is used in the default log configuration.
`logging.pattern.console`	`CONSOLE_LOG_PATTERN`	The log pattern to use on the console (stdout).
`logging.pattern.dateformat`	`LOG_DATEFORMAT_PATTERN`	Appender pattern for log date format.
`logging.charset.console`	`CONSOLE_LOG_CHARSET`	The charset to use for console logging.
`logging.threshold.console`	`CONSOLE_LOG_THRESHOLD`	The log level threshold to use for console logging.
`logging.pattern.file`	`FILE_LOG_PATTERN`	The log pattern to use in a file (if `LOG_FILE` is enabled).
`logging.charset.file`	`FILE_LOG_CHARSET`	The charset to use for file logging (if `LOG_FILE` is enabled).
`logging.threshold.file`	`FILE_LOG_THRESHOLD`	The log level threshold to use for file logging.
`logging.pattern.level`	`LOG_LEVEL_PATTERN`	The format to use when rendering the log level (default `%5p`).
`PID`	`PID`

使用 logback，可多使用這些參數

Spring Environment	System Property	Comments
`logging.logback.rollingpolicy.file-name-pattern`	`LOGBACK_ROLLINGPOLICY_FILE_NAME_PATTERN`	Pattern for rolled-over log file names (default `${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz`).
`logging.logback.rollingpolicy.clean-history-on-start`	`LOGBACK_ROLLINGPOLICY_CLEAN_HISTORY_ON_START`	Whether to clean the archive log files on startup.
`logging.logback.rollingpolicy.max-file-size`	`LOGBACK_ROLLINGPOLICY_MAX_FILE_SIZE`	Maximum log file size.
`logging.logback.rollingpolicy.total-size-cap`	`LOGBACK_ROLLINGPOLICY_TOTAL_SIZE_CAP`	Total size of log backups to be kept.
`logging.logback.rollingpolicy.max-history`	`LOGBACK_ROLLINGPOLICY_MAX_HISTORY`

Logback Extension

logback-spring.xml 裡面有幾個 logback extensions

profile-specific cofiguration

根據 active profile，<springProfile> 可 include/exclude 部分設定

<springProfile name="staging">
    <!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>

<springProfile name="dev | staging">
    <!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</springProfile>

<springProfile name="!production">
    <!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>

environment properties

<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"
        defaultValue="localhost"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
    <remoteHost>${fluentHost}</remoteHost>
    ...
</appender>

example

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <property name="LOG_PATH" value="/var/log/blog"/>
    <property name="LOG_FILENAME" value="spring-profiles"/>

    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
    <include resource="org/springframework/boot/logging/logback/console-appender.xml"/>

    <springProfile name="default,ide">
        <root level="INFO">
            <appender-ref ref="CONSOLE"/>
        </root>
    </springProfile>

    <springProfile name="test,prod">
        <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
            <encoder>
                <pattern>${FILE_LOG_PATTERN}</pattern>
            </encoder>
            <file>${LOG_PATH}/${LOG_FILENAME}.log</file>
            <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
                <fileNamePattern>${LOG_PATH}/${LOG_FILENAME}-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
                <maxHistory>7</maxHistory>
                <maxFileSize>100MB</maxFileSize>
                <totalSizeCap>1GB</totalSizeCap>
            </rollingPolicy>
        </appender>

        <root level="INFO">
            <appender-ref ref="FILE"/>
        </root>
    </springProfile>

</configuration>

Log4j2 Extension

可在 log4j2-spring.xml 設定使用

profile-specific configuration

<SpringProfile name="staging">
    <!-- configuration to be enabled when the "staging" profile is active -->
</SpringProfile>

<SpringProfile name="dev | staging">
    <!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</SpringProfile>

<SpringProfile name="!production">
    <!-- configuration to be enabled when the "production" profile is not active -->
</SpringProfile>

Environment Properties Lookup

<Properties>
    <Property name="applicationName">${spring:spring.application.name}</Property>
</Properties>

log4j2 system properties

ex: ConsoleAppender 在 windows 使用 Jansi

log4j2.skipJansi=false

2025/03/31

SpringBoot3 - Spring Boot Log