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208 lines
10 KiB
Markdown
208 lines
10 KiB
Markdown
# logger
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[`logger`在线教程](https://arthas.aliyun.com/doc/arthas-tutorials?language=cn&id=command-logger)
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::: tip
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查看 logger 信息，更新 logger level
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:::
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### 使用参考
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#### 查看所有 logger 信息
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以下面的`logback.xml`为例：
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<configuration>
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<appender name="APPLICATION" class="ch.qos.logback.core.rolling.RollingFileAppender">
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<file>app.log</file>
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<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
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<fileNamePattern>mylog-%d{yyyy-MM-dd}.%i.txt</fileNamePattern>
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<maxFileSize>100MB</maxFileSize>
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<maxHistory>60</maxHistory>
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<totalSizeCap>2GB</totalSizeCap>
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</rollingPolicy>
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<encoder>
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<pattern>%logger{35} - %msg%n</pattern>
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</encoder>
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</appender>
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<appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
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<appender-ref ref="APPLICATION" />
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</appender>
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<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
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<encoder>
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<pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n
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</pattern>
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<charset>utf8</charset>
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</encoder>
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</appender>
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<root level="INFO">
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<appender-ref ref="CONSOLE" />
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<appender-ref ref="ASYNC" />
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</root>
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</configuration>
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```
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使用`logger`命令打印的结果是：
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```bash
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[arthas@2062]$ logger
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name ROOT
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level INFO
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effectiveLevel INFO
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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appenders name CONSOLE
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class ch.qos.logback.core.ConsoleAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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target System.out
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name APPLICATION
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class ch.qos.logback.core.rolling.RollingFileAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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file app.log
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name ASYNC
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class ch.qos.logback.classic.AsyncAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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appenderRef [APPLICATION]
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```
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从`appenders`的信息里，可以看到
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- `CONSOLE` logger 的 target 是`System.out`
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- `APPLICATION` logger 是`RollingFileAppender`，它的 file 是`app.log`
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- `ASYNC`它的`appenderRef`是`APPLICATION`，即异步输出到文件里
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#### 查看指定名字的 logger 信息
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```bash
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[arthas@2062]$ logger -n org.springframework.web
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name org.springframework.web
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level null
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effectiveLevel INFO
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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```
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#### 查看指定 classloader 的 logger 信息
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注意 hashcode 是变化的，需要先查看当前的 ClassLoader 信息，提取对应 ClassLoader 的 hashcode。
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如果你使用`-c`，你需要手动输入 hashcode：`-c <hashcode>`
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```bash
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[arthas@2062]$ logger -c 2a139a55
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name ROOT
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level DEBUG
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effectiveLevel DEBUG
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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appenders name CONSOLE
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class ch.qos.logback.core.ConsoleAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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target System.out
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name APPLICATION
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class ch.qos.logback.core.rolling.RollingFileAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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file app.log
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name ASYNC
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class ch.qos.logback.classic.AsyncAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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appenderRef [APPLICATION]
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```
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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：
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`logger --classLoaderClass sun.misc.Launcher$AppClassLoader`
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- 注: 这里 classLoaderClass 在 java 8 是 sun.misc.Launcher$AppClassLoader，而java 11的classloader是jdk.internal.loader.ClassLoaders$AppClassLoader。
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`--classLoaderClass` 的值是 ClassLoader 的类名，只有匹配到唯一的 ClassLoader 实例时才能工作，目的是方便输入通用命令，而`-c <hashcode>`是动态变化的。
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#### 更新 logger level
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```bash
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[arthas@2062]$ logger --name ROOT --level debug
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update logger level success.
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```
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#### 指定 classloader 更新 logger level
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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。
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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：
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```bash
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[arthas@2062]$ logger -c 2a139a55 --name ROOT --level debug
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```
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#### 查看没有 appender 的 logger 的信息
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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`。
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注意，通常输出结果会很长。
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```bash
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[arthas@2062]$ logger --include-no-appender
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name ROOT
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level DEBUG
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effectiveLevel DEBUG
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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appenders name CONSOLE
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class ch.qos.logback.core.ConsoleAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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target System.out
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name APPLICATION
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class ch.qos.logback.core.rolling.RollingFileAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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file app.log
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name ASYNC
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class ch.qos.logback.classic.AsyncAppender
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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appenderRef [APPLICATION]
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name com
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level null
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effectiveLevel DEBUG
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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name com.alibaba
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class ch.qos.logback.classic.Logger
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classLoader sun.misc.Launcher$AppClassLoader@2a139a55
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classLoaderHash 2a139a55
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level null
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effectiveLevel DEBUG
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additivity true
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codeSource file:/Users/hengyunabc/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar
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...
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```
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