Java如何使用arthas修改日志級別

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arthas能夠更改日志的級別，下面是logger的用法

查看logger信息，更新logger level

查看所有logger信息 logger

以下面的logback.xml為例：

<?xml version="1.0" encoding="UTF-8"?><configuration>    <appender name="APPLICATION" class="ch.qos.logback.core.rolling.RollingFileAppender">        <file>app.log</file>        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">            <fileNamePattern>mylog-%d{yyyy-MM-dd}.%i.txt</fileNamePattern>            <maxFileSize>100MB</maxFileSize>            <maxHistory>60</maxHistory>            <totalSizeCap>2GB</totalSizeCap>        </rollingPolicy>        <encoder>            <pattern>%logger{35} - %msg%n</pattern>        </encoder>    </appender>     <appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">        <appender-ref ref="APPLICATION" />    </appender>     <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">        <encoder>            <pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n            </pattern>            <charset>utf8</charset>        </encoder>    </appender>     <root level="INFO">        <appender-ref ref="CONSOLE" />        <appender-ref ref="ASYNC" />    </root></configuration>

sc -d *FormulaEngine |grepclassLoaderHash

sc -d FormulaEngine.class*

使用logger命令打印的結果是：

[arthas@2062]$ logger name                                   ROOT class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  INFO effectiveLevel                         INFO additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar appenders                              name            CONSOLE                                        class           ch.qos.logback.core.ConsoleAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        target          System.out                                        name            APPLICATION                                        class           ch.qos.logback.core.rolling.RollingFileAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        file            app.log                                        name            ASYNC                                        class           ch.qos.logback.classic.AsyncAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        appenderRef     [APPLICATION]

從appenders的信息里，可以看到

CONSOLElogger的target是System.out

APPLICATIONlogger是RollingFileAppender，它的file是app.log

ASYNC它的appenderRef是APPLICATION，即異步輸出到文件里

查看指定名字的logger信息 logger -n org.springframework.web

[arthas@2062]$ logger -n org.springframework.web name                                   org.springframework.web class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  null effectiveLevel                         INFO additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar

查看指定classloader的logger信息

注意hashcode是變化的，需要先查看當前的ClassLoader信息，提取對應ClassLoader的hashcode。

如果你使用-c，你需要手動輸入hashcode：-c <hashcode>

[arthas@2062]$ logger -c 2a139a55 name                                   ROOT class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  DEBUG effectiveLevel                         DEBUG additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar appenders                              name            CONSOLE                                        class           ch.qos.logback.core.ConsoleAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        target          System.out                                        name            APPLICATION                                        class           ch.qos.logback.core.rolling.RollingFileAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        file            app.log                                        name            ASYNC                                        class           ch.qos.logback.classic.AsyncAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        appenderRef     [APPLICATION]

對于只有唯一實例的ClassLoader可以通過--classLoaderClass指定class name，使用起來更加方便：

logger --classLoaderClass sun.misc.Launcher$AppClassLoader

注: 這里classLoaderClass 在 java 8 是 sun.misc.Launcher$AppClassLoader，而java 11的classloader是jdk.internal.loader.ClassLoaders$AppClassLoader。

--classLoaderClass的值是ClassLoader的類名，只有匹配到唯一的ClassLoader實例時才能工作，目的是方便輸入通用命令，而-c <hashcode>是動態變化的。

更新logger level 找到需要修改日志級別的類

命令：

sc -d FreeResourceQueryActionImpl.class*

或者

sc -d *FreeResourceQueryActionImpl | grep classLoaderHash

結果：目的就是為了找出classLoaderHash

修改

[arthas@2062]$ logger --name ROOT --level debugupdate logger level success.

指定classloader更新 logger level

默認情況下，logger命令會在SystemClassloader下執行，如果應用是傳統的war應用，或者spring boot fat jar啟動的應用，那么需要指定classloader。

可以先用sc -d yourClassName來查看具體的 classloader hashcode，然后在更新level時指定classloader：

[arthas@2062]$ logger -c 2a139a55 --name ROOT --level debug

查看沒有appender的logger的信息

默認情況下，logger命令只打印有appender的logger的信息。如果想查看沒有appender的logger的信息，可以加上參數--include-no-appender。

注意，通常輸出結果會很長。

[arthas@2062]$ logger --include-no-appender name                                   ROOT class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  DEBUG effectiveLevel                         DEBUG additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar appenders                              name            CONSOLE                                        class           ch.qos.logback.core.ConsoleAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        target          System.out                                        name            APPLICATION                                        class           ch.qos.logback.core.rolling.RollingFileAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        file            app.log                                        name            ASYNC                                        class           ch.qos.logback.classic.AsyncAppender                                        classLoader     sun.misc.Launcher$AppClassLoader@2a139a55                                        classLoaderHash 2a139a55                                        appenderRef     [APPLICATION]  name                                   com class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  null effectiveLevel                         DEBUG additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar  name                                   com.alibaba class                                  ch.qos.logback.classic.Logger classLoader                            sun.misc.Launcher$AppClassLoader@2a139a55 classLoaderHash                        2a139a55 level                                  null effectiveLevel                         DEBUG additivity                             true codeSource                             file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar...

退出arthas

為了不影響性能，解決完問題需要退出arthas

如果只是退出當前的連接，可以用quit或者exit命令。Attach到目標進程上的arthas還會繼續運行，端口會保持開放，下次連接時可以直接連接上。

如果想完全退出arthas，可以執行stop命令。

退出之前恢復原來的日志級別

感謝各位的閱讀，以上就是“Java如何使用arthas修改日志級別”的內容了，經過本文的學習后，相信大家對Java如何使用arthas修改日志級別這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！