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Java使用arthas修改日志級(jí)別詳解

更新時(shí)間：2022年06月17日 09:48:56 作者：奇點(diǎn)_97

在我們線上環(huán)境中，一般不會(huì)開啟debug級(jí)別的日志，為了提高性能?info和warning級(jí)別的日志也一般不會(huì)打印出來(lái)，那么如果遇到線上問(wèn)題，除了使用arthas定位問(wèn)題，想通過(guò)查詢?nèi)罩緛?lái)實(shí)現(xiàn)問(wèn)題定位，如何查看logger信息，更新logger?level呢，下面我們來(lái)了解arthas修改日志級(jí)別

查看所有l(wèi)ogger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(jié)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(dāng)前的ClassLoader信息，提取對(duì)應(yīng)ClassLoader的hashcode。

如果你使用-c，你需要手動(dòng)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(duì)于只有唯一實(shí)例的ClassLoader可以通過(guò)--classLoaderClass指定class name，使用起來(lái)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(shí)例時(shí)才能工作，目的是方便輸入通用命令，而-c <hashcode>是動(dòng)態(tài)變化的。

更新logger level

找到需要修改日志級(jí)別的類

命令：

sc -d FreeResourceQueryActionImpl.class*

或者

sc -d *FreeResourceQueryActionImpl | grep classLoaderHash

結(jié)果：目的就是為了找出classLoaderHash

修改

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

編輯指定classloader更新 logger level

默認(rèn)情況下，logger命令會(huì)在SystemClassloader下執(zhí)行，如果應(yīng)用是傳統(tǒng)的war應(yīng)用，或者spring boot fat jar啟動(dòng)的應(yīng)用，那么需要指定classloader。

可以先用sc -d yourClassName來(lái)查看具體的 classloader hashcode，然后在更新level時(shí)指定classloader：

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

查看沒(méi)有appender的logger的信息

默認(rèn)情況下，logger命令只打印有appender的logger的信息。如果想查看沒(méi)有appender的logger的信息，可以加上參數(shù)--include-no-appender。

注意，通常輸出結(jié)果會(huì)很長(zhǎng)。

[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
...