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我们在系统中一般都会打印一些日志，并且在开发、测试、生产各个环境中的日志级别可能不一样。在开发过程中为了方便调试打印了很多debug日志，但是生产环境为了性能，为了节约存储资源，我们会将日志级别设置为info或error较高的级别，只保留一些关键的必要的日志。
当线上出现问题需要排查时，最有效的方式是分析系统日志。此时因为线上环境日志级别较高，对排查问题有一定的阻碍，为了快速响应线上问题，我们需要更全面的日志帮助排查问题，传统的做法是修改日志级别重启项目。
为了兼顾性能和快速响应线上问题，实现不重启项目的前提下动态修改日志级别。通过使用该功能，可以在需要解决线上问题时，实时调整线上日志输出级别，获取全面的Debug日志，帮助工程师提高定位问题的效率。
本文列举了几种实现方案，已经验证可用，供大家参考。
在Spring Boot项目中可以通过LoggingSystem来获取或修改日志配置。
1.1 获取日志Logger配置
通过LoggingSystem API getLoggerConfigurations获取所有Logger配置
List loggerConfigs = loggingSystem.getLoggerConfigurations();
1.2 修改日志级别
通过调用LoggingSystem API setLogLevel设置包或具体Logger的日志级别，修改成功，立即生效。
@Autowired
private LoggingSystem loggingSystem;
@RequestMapping(value = "/changeLogLevel", method = RequestMethod.POST)
public void changeLogLevel(String loggerName, String newLevel) {
log.info("更新日志级别:{}", newLevel);
LogLevel level = LogLevel.valueOf(newLevel.toUpperCase());
loggingSystem.setLogLevel(loggerName, level);
log.info("更新日志级别:{} 更新完毕", newLevel);
}
参考美团技术文章：https://tech.meituan.com/2017/02/17/change-log-level.html
想必现在的业务系统基本都是采用SLF4J日志框架吧，在应用初始化时，SLF4J会绑定具体的日志框架，如Log4j、Logback或Log4j2等。具体源码如下(slf4j-api-1.7.7)：
private final static void bind() {
try {
// 查找classpath下所有的StaticLoggerBinder类。
Set<URL> staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
// 每一个slf4j桥接包中都有一个org.slf4j.impl.StaticLoggerBinder类，该类实现了LoggerFactoryBinder接口。
// the next line does the binding
StaticLoggerBinder.getSingleton();
INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
reportActualBinding(staticLoggerBinderPathSet);
fixSubstitutedLoggers();
...
}
findPossibleStaticLoggerBinderPathSet方法用来查找当前classpath下所有的org.slf4j.impl.StaticLoggerBinder类。每一个slf4j桥接包中都有一个StaticLoggerBinder类，该类实现了LoggerFactoryBinder接口。具体绑定到哪一个日志框架则取决于类加载顺序。
动态调整日志级别具体实现步骤如下：
2.1 初始化
确定所使用的日志框架，获取配置文件中所有的Logger内存实例，并将它们的引用缓存到Map容器中。
String type = StaticLoggerBinder.getSingleton().getLoggerFactoryClassStr();
if (LogConstant.LOG4J_LOGGER_FACTORY.equals(type)) {
logFrameworkType = LogFrameworkType.LOG4J;
Enumeration enumeration = org.apache.log4j.LogManager.getCurrentLoggers();
while (enumeration.hasMoreElements()) {
org.apache.log4j.Logger logger = (org.apache.log4j.Logger) enumeration.nextElement();
if (logger.getLevel() != null) {
loggerMap.put(logger.getName(), logger);
}
}
org.apache.log4j.Logger rootLogger = org.apache.log4j.LogManager.getRootLogger();
loggerMap.put(rootLogger.getName(), rootLogger);
} else if (LogConstant.LOGBACK_LOGGER_FACTORY.equals(type)) {
logFrameworkType = LogFrameworkType.LOGBACK;
ch.qos.logback.classic.LoggerContext loggerContext = (ch.qos.logback.classic.LoggerContext) LoggerFactory.getILoggerFactory();
for (ch.qos.logback.classic.Logger logger : loggerContext.getLoggerList()) {
if (logger.getLevel() != null) {
loggerMap.put(logger.getName(), logger);
}
}
ch.qos.logback.classic.Logger rootLogger = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
loggerMap.put(rootLogger.getName(), rootLogger);
} else if (LogConstant.LOG4J2_LOGGER_FACTORY.equals(type)) {
logFrameworkType = LogFrameworkType.LOG4J2;
org.apache.logging.log4j.core.LoggerContext loggerContext = (org.apache.logging.log4j.core.LoggerContext) org.apache.logging.log4j.LogManager.getContext(false);
Map<String, org.apache.logging.log4j.core.config.LoggerConfig> map = loggerContext.getConfiguration().getLoggers();
for (org.apache.logging.log4j.core.config.LoggerConfig loggerConfig : map.values()) {
String key = loggerConfig.getName();
if (StringUtils.isBlank(key)) {
key = "root";
}
loggerMap.put(key, loggerConfig);
}
} else {
logFrameworkType = LogFrameworkType.UNKNOWN;
LOG.error("Log框架无法识别: type={}", type);
}
2.2 获取Logger列表
从本地Map容器取出，封装成包含loggerName、logLevel的对象。
private String getLoggerList() {
JSONObject result = new JSONObject();
result.put("logFramework", logFrameworkType);
JSONArray loggerList = new JSONArray();
for (ConcurrentMap.Entry<String, Object> entry : loggerMap.entrySet()) {
JSONObject loggerJSON = new JSONObject();
loggerJSON.put("loggerName", entry.getKey());
if (logFrameworkType == LogFrameworkType.LOG4J) {
org.apache.log4j.Logger targetLogger = (org.apache.log4j.Logger) entry.getValue();
loggerJSON.put("logLevel", targetLogger.getLevel().toString());
} else if (logFrameworkType == LogFrameworkType.LOGBACK) {
ch.qos.logback.classic.Logger targetLogger = (ch.qos.logback.classic.Logger) entry.getValue();
loggerJSON.put("logLevel", targetLogger.getLevel().toString());
} else if (logFrameworkType == LogFrameworkType.LOG4J2) {
org.apache.logging.log4j.core.config.LoggerConfig targetLogger = (org.apache.logging.log4j.core.config.LoggerConfig) entry.getValue();
loggerJSON.put("logLevel", targetLogger.getLevel().toString());
} else {
loggerJSON.put("logLevel", "Logger的类型未知,无法处理!");
}
loggerList.add(loggerJSON);
}
result.put("loggerList", loggerList);
LOG.info("getLoggerList: result={}", result.toString());
return result.toString();
}
结果：
{
"loggerList": [
{
"logLevel": "OFF",
"loggerName": "org.springframework.ldap"
},
{
"logLevel": "INFO",
"loggerName": "ROOT"
},
{
"logLevel": "OFF",
"loggerName": "com.sun.jersey.api.client"
},
{
"logLevel": "OFF",
"loggerName": "com.netflix.discovery"
}
],
"logFramework": "LOGBACK"
}
2.3 修改日志级别
通过调用具体的日志框架提供的API setLevel修改Logger日志级别，修改成功，立即生效。
private String setLogLevel(JSONArray data) {
LOG.info("setLogLevel: data={}", data);
List<LoggerBean> loggerList = parseJsonData(data);
if (CollectionUtils.isEmpty(loggerList)) {
return "";
}
for (LoggerBean loggerbean : loggerList) {
Object logger = loggerMap.get(loggerbean.getName());
if (logger == null) {
throw new RuntimeException("需要修改日志级别的Logger不存在");
}
if (logFrameworkType == LogFrameworkType.LOG4J) {
org.apache.log4j.Logger targetLogger = (org.apache.log4j.Logger) logger;
org.apache.log4j.Level targetLevel = org.apache.log4j.Level.toLevel(loggerbean.getLevel());
targetLogger.setLevel(targetLevel);
} else if (logFrameworkType == LogFrameworkType.LOGBACK) {
ch.qos.logback.classic.Logger targetLogger = (ch.qos.logback.classic.Logger) logger;
ch.qos.logback.classic.Level targetLevel = ch.qos.logback.classic.Level.toLevel(loggerbean.getLevel());
targetLogger.setLevel(targetLevel);
} else if (logFrameworkType == LogFrameworkType.LOG4J2) {
org.apache.logging.log4j.core.config.LoggerConfig loggerConfig = (org.apache.logging.log4j.core.config.LoggerConfig) logger;
org.apache.logging.log4j.Level targetLevel = org.apache.logging.log4j.Level.toLevel(loggerbean.getLevel());
loggerConfig.setLevel(targetLevel);
org.apache.logging.log4j.core.LoggerContext ctx = (org.apache.logging.log4j.core.LoggerContext) org.apache.logging.log4j.LogManager.getContext(false);
ctx.updateLoggers(); // This causes all Loggers to refetch information from their LoggerConfig.
} else {
throw new RuntimeException("Logger的类型未知,无法处理!");
}
}
return "success";
}
3.1 引入依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
3.2 开启日志端点配置
# 由于Spring Boot 2.x默认只暴露 /health 以及 /info 端点，
# 而日志控制需要用到 /loggers 端点，故而需要设置将其暴露。当然把loggers替换成*也是可以的；开启所有！
management:
endpoints:
web:
exposure:
include: 'loggers'
可以通过访问URL/actuator/loggers/后加包名或者类名来查询指定包或者类的当前日志级别。
curl http://127.0.0.1:8007/manage/actuator/loggers/com.trrt.ep
{"configuredLevel":"DEBUG","effectiveLevel":"DEBUG"}
3.3 查看所有Logger
http://127.0.0.1:8007/manage/actuator/loggers
3.4 修改日志级别
可以通过访问URL/actuator/loggers/后加包名或者类名来修改指定包或者类的当前日志级别。
curl -X POST "http://127.0.0.1:8007/manage/actuator/loggers/com.trrt.ep" -H "Content-Type: application/json;charset=UTF-8" --data '{"configuredLevel":"debug"}'
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