Spring Boot Logging Level设置为off时Bug

发博词

阿里云的KAFA有一个特性就是会主动关闭空闲的链接，这样导致的问题就是客户端程序会不停的报如下的异常信息：

java.io.IOException: 远程主机强迫关闭了一个现有的连接。
  at sun.nio.ch.SocketDispatcher.write0(Native Method) ~[na:1.8.0_112]
  at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:51) ~[na:1.8.0_112]
  at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93) ~[na:1.8.0_112]
  at sun.nio.ch.IOUtil.write(IOUtil.java:65) ~[na:1.8.0_112]
  at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:471) ~[na:1.8.0_112]
  at org.apache.kafka.common.network.SslTransportLayer.flush(SslTransportLayer.java:195) ~[kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.SslTransportLayer.close(SslTransportLayer.java:163) ~[kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.utils.Utils.closeAll(Utils.java:731) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.KafkaChannel.close(KafkaChannel.java:54) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.Selector.doClose(Selector.java:540) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.Selector.close(Selector.java:531) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.Selector.pollSelectionKeys(Selector.java:378) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.common.network.Selector.poll(Selector.java:303) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.clients.NetworkClient.poll(NetworkClient.java:349) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:226) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.clients.consumer.KafkaConsumer.pollOnce(KafkaConsumer.java:1048) [kafka-clients-0.10.2.0.jar:na]
  at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:995) [kafka-clients-0.10.2.0.jar:na]
  at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.run(KafkaMessageListenerContainer.java:558) [spring-kafka-1.1.6.RELEASE.jar:na]
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_112]
  at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_112]
  at java.lang.Thread.run(Thread.java:745) [na:1.8.0_112]      

而这个异常信息，其实意义不大，而且会一直出，所以就有了需求想要关闭kafka这个包的日志。

临时解决方法

Spring Boot Logging将LogLevel抽象为6个级别，还有一个OFF，是配置关闭日志：

/**
 * Logging levels supported by a {@link LoggingSystem}.
 *
 * @author Phillip Webb
 */
public enum LogLevel {

  TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF

}      

但是将某个包的日志级别设置为OFF时，控制台会报如下的信息：

2017-08-24 13:52:12.882 ERROR 12672 --- [           main] o.s.cloud.logging.LoggingRebinder        : Cannot set level: false for 'org.apache.kafka'      

定位到LoggingRebinder#setLogLevel方法：

private void setLogLevel(LoggingSystem system, Environment environment, String name,
      String level) {
    try {
      if (name.equalsIgnoreCase("root")) {
        name = null;
      }
      level = environment.resolvePlaceholders(level);
      system.setLogLevel(name, LogLevel.valueOf(level.toUpperCase()));
    }
    catch (RuntimeException ex) {
      this.logger.error("Cannot set level: " + level + " for '" + name + "'");
    }
  }      

此时 RuntimeException ex的异常信息如下

java.lang.IllegalArgumentException: No enum constant org.springframework.boot.logging.LogLevel.FALSE      

查看level = environment.resolvePlaceholders(level)的值，确实是字符串false而不是off，所以LogLevel.valueOf(level.toUpperCase())在解析的时候就报错了。