Java如何使用arthas修改日志级别

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arthas能够更改日志的级别，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为例：

<?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命令打印的结果是：

[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]

从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，即异步输出到文件里

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是变化的，需要先查看当前的ClassLoader信息，提取对应ClassLoader的hashcode。

如果你使用-c，你需要手动输入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]

对于只有唯一实例的ClassLoader可以通过--classLoaderClass指定class name，使用起来更加方便：

logger --classLoaderClass sun.misc.Launcher$AppClassLoader

注: 这里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的类名，只有匹配到唯一的ClassLoader实例时才能工作，目的是方便输入通用命令，而-c <hashcode>是动态变化的。

更新logger level 找到需要修改日志级别的类

命令：

sc -d FreeResourceQueryActionImpl.class*

或者

sc -d *FreeResourceQueryActionImpl | grep classLoaderHash

结果：目的就是为了找出classLoaderHash

修改

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

指定classloader更新 logger level

默认情况下，logger命令会在SystemClassloader下执行，如果应用是传统的war应用，或者Spring Boot fat jar启动的应用，那么需要指定classloader。

可以先用sc -d yourClassName来查看具体的 classloader hashcode，然后在更新level时指定classloader：

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

查看没有appender的logger的信息

默认情况下，logger命令只打印有appender的logger的信息。如果想查看没有appender的logger的信息，可以加上参数--include-no-appender。

注意，通常输出结果会很长。

[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

为了不影响性能，解决完问题需要退出arthas

如果只是退出当前的连接，可以用quit或者exit命令。Attach到目标进程上的arthas还会继续运行，端口会保持开放，下次连接时可以直接连接上。

如果想完全退出arthas，可以执行stop命令。

退出之前恢复原来的日志级别

感谢各位的阅读，以上就是“Java如何使用arthas修改日志级别”的内容了，经过本文的学习后，相信大家对Java如何使用arthas修改日志级别这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是编程网，小编将为大家推送更多相关知识点的文章，欢迎关注！