Jenkins的slave异常：Exception in thread "main" java.lang.ClassNotFoundException: hudson.remoting.Launcher

当任务分配到slave上执行时，报如下错误：

Parsing POMs
Established TCP socket on 38257
maven33-agent.jar already up to date
maven33-interceptor.jar already up to date
maven3-interceptor-commons.jar already up to date
[b012ef95d917292e062fe3d70c7a9b01] $ java -cp /var/lib/jenkins/maven33-agent.jar:/usr/install/apache-maven-3.3.9/boot/plexus-classworlds-2.5.2.jar:/usr/install/apache-maven-3.3.9/conf/logging jenkins.maven3.agent.Maven33Main /usr/install/apache-maven-3.3.9 /var/lib/jenkins/slave.jar /var/lib/jenkins/maven33-interceptor.jar /var/lib/jenkins/maven3-interceptor-commons.jar 38257
Exception in thread "main" java.lang.ClassNotFoundException: hudson.remoting.Launcher
	at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(ClassRealm.java:271)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:247)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:239)
	at jenkins.maven3.agent.Maven33Main.main(Maven33Main.java:133)
	at jenkins.maven3.agent.Maven33Main.main(Maven33Main.java:64)

ERROR: Failed to parse POMs
java.io.EOFException: unexpected stream termination
	at hudson.remoting.ChannelBuilder.negotiate(ChannelBuilder.java:365)
	at hudson.remoting.ChannelBuilder.build(ChannelBuilder.java:310)
	at hudson.slaves.Channels.forProcess(Channels.java:115)
	at hudson.maven.AbstractMavenProcessFactory.newProcess(AbstractMavenProcessFactory.java:294)
	at hudson.maven.ProcessCache.get(ProcessCache.java:236)
	at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:798)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:534)
	at hudson.model.Run.execute(Run.java:1730)
	at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:544)
	at hudson.model.ResourceController.execute(ResourceController.java:97)
	at hudson.model.Executor.run(Executor.java:405)

搜索了下解决办法：说是重连下slave。照做，问题解决。看下master连接slave的日志信息，我想原因应该是我修改过slave的环境变量hostname。不知道修改其他环境变量是否也会有同样的影响。
从日志信息上看，有一个获取slave环境变量的过程