【spark】Could not initialize class org.apache.spark.internal.config.package$

Bertha 。 2022-05-14 00:16 293阅读 0赞

# Could not initialize class org.apache.spark.internal.config.package$ #

*  Could not initialize class org.apache.spark.internal.config.package$
    
     *  问题描述
     *  解决思路
     *  总结

## 问题描述 ##

有一个`spark sql`项目，使用`local[*]`模式测试，在本地一切OK，但是放到服务器上测试的时候，一build`SparkSession`就报错：

[2018-08-30 08:42:00] [Thread-225] [WARN] [org.apache.spark.internal.Logging$class:66] Another SparkContext is being constructed (or threw an exception in its constructor).  This may indicate an error, since only one SparkContext may be running in this JVM (see SPARK-2243). The other SparkContext was created at:
    org.apache.spark.sql.SparkSession$Builder.getOrCreate(SparkSession.scala:910)
    com.enmo.dbaas.util.MongoSparkSession$.get(MongoSparkSession.scala:25)
    com.enmo.dbaas.util.MongoSparkSession$.getDefault(MongoSparkSession.scala:30)
    com.enmo.dbaas.controller.ComputeTriggerController$$anon$1.run(ComputeTriggerController.scala:66)
    java.lang.Thread.run(Thread.java:748)
    [2018-08-30 08:42:00] [Thread-225] [INFO] [org.apache.spark.internal.Logging$class:54] Running Spark version 2.2.1
    [2018-08-30 08:45:00] [http-nio-8098-exec-10] [WARN] [org.apache.spark.internal.Logging$class:66] Another SparkContext is being constructed (or threw an exception in its constructor).  This may indicate an error, since only one SparkContext may be running in this JVM (see SPARK-2243). The other SparkContext was created at:
    org.apache.spark.sql.SparkSession$Builder.getOrCreate(SparkSession.scala:910)
    com.enmo.dbaas.util.MongoSparkSession$.get(MongoSparkSession.scala:25)
    com.enmo.dbaas.util.MongoSparkSession$.getDefault(MongoSparkSession.scala:30)
    com.enmo.dbaas.controller.ComputeTriggerController$$anon$1.run(ComputeTriggerController.scala:66)
    java.lang.Thread.run(Thread.java:748)
    [2018-08-30 08:45:00] [http-nio-8098-exec-10] [INFO] [org.apache.spark.internal.Logging$class:54] Running Spark version 2.2.1
    [2018-08-30 08:45:00] [http-nio-8098-exec-10] [ERROR] [org.apache.juli.logging.DirectJDKLog:182] Servlet.service() for servlet [dispatcherServlet] in context with path [/dbaasMonitorOfflineCompute] threw exception [Handler dispatch failed; nested exception is java.lang.NoClassDefFoundError: Could not initialize class org.apache.spark.internal.config.package$] with root cause
    java.lang.NoClassDefFoundError: Could not initialize class org.apache.spark.internal.config.package$
        at org.apache.spark.SparkConf.validateSettings(SparkConf.scala:546)
        at org.apache.spark.SparkContext.<init>(SparkContext.scala:373)
        at org.apache.spark.SparkContext$.getOrCreate(SparkContext.scala:2516)
        at org.apache.spark.sql.SparkSession$Builder$$anonfun$6.apply(SparkSession.scala:918)
        at org.apache.spark.sql.SparkSession$Builder$$anonfun$6.apply(SparkSession.scala:910)
        at scala.Option.getOrElse(Option.scala:121)
        at org.apache.spark.sql.SparkSession$Builder.getOrCreate(SparkSession.scala:910)
        at com.enmo.dbaas.util.MongoSparkSession$.get(MongoSparkSession.scala:25)
        at com.enmo.dbaas.util.MongoSparkSession$.getDefault(MongoSparkSession.scala:30)
        at com.enmo.dbaas.controller.ComputeTriggerController.segment(ComputeTriggerController.scala:175)
        at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)

## 解决思路 ##

这就奇了怪了，报`Could not initialize class xxx`这个错，一般是`JVM`在加载类的时候，初始化静态变量或者执行静态代码块的时候报错，后面任何时候任何地方使用这个类都会报`Could not initialize class xxx`，只有在第一次初始化这个类的时候会抛出导致静态变量初始化失败或静态代码块执行失败的真实错误。

看了一下`org.apache.spark.internal.config.package`这个类，是一个`scala`的`package object`类，简单认为就是一个类包含多个静态变量或静态内部类。看来上面的猜想是对的。

马上重启项目，触发错误，然而第一次加载类并没有抛出真实错误（或者是spark捕获了异常并没有抛出），原因不得而知；分析了`StcakTrace`，找到相关的代码行，发现真的是调用`org.apache.spark.internal.config.package`的一个静态变量，不过没有抛出异常实在太让人迷惑了，思路一度中断。

错误里面包含

Another SparkContext is being constructed (or threw an exception in its constructor). This may indicate an error, since only one SparkContext may be running in this JVM (see SPARK-2243).

这样的描述，走了一些弯路。Google半天，发现一个方法是设置环境变量`SPARK_LOCAL_IP=#{YOUR_SERVER_IP}`，这个方法是确实可以，但是需要加环境变量，这个项目之前运行都是没有问题的，突然就不行了，一定得找到问题所在。

报错的地方是在`org.apache.spark.SparkConf` 546行：

546 val encryptionEnabled = get(NETWORK_ENCRYPTION_ENABLED) || get(SASL_ENCRYPTION_ENABLED)

猜想是网络问题，本地无法复现，准备远程调试。

首先用`Debug`模式重启项目，并制定远程端口(注意防火墙设置)：

java -jar -Xms1024m -Xmx1024m -Xdebug -Xrunjdwp:transport=dt_socket,suspend=n,server=y,address=55555 a.jar

然后打开`ItelliJ IDEA`，导入对应的项目：  
![这里写图片描述][70]  
![这里写图片描述][70 1]  
![这里写图片描述][70 2]

server上启动项目后，马上debug刚刚配置的remote JVM，然后触发错误，断点到了`org.apache.spark.SparkConf` 546行，step over后马上报错：

[2018-08-30 14:36:03] [http-nio-8098-exec-4] [ERROR] [org.apache.juli.logging.DirectJDKLog:182] Servlet.service() for servlet [dispatcherServlet] in context with path [/xx] threw exception [Handler dispatch failed; nested exception is java.lang.ExceptionInInitializerError] with root cause
    java.net.UnknownHostException: dev: Name or service not known
        at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928)
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323)
        at java.net.InetAddress.getLocalHost(InetAddress.java:1500)
        at org.apache.spark.util.Utils$.findLocalInetAddress(Utils.scala:891)
        at org.apache.spark.util.Utils$.org$apache$spark$util$Utils$$localIpAddress$lzycompute(Utils.scala:884)
        at org.apache.spark.util.Utils$.org$apache$spark$util$Utils$$localIpAddress(Utils.scala:884)
        at org.apache.spark.util.Utils$$anonfun$localHostName$1.apply(Utils.scala:941)
    	at org.apache.spark.util.Utils$$anonfun$localHostName$1.apply(Utils.scala:941)
        at scala.Option.getOrElse(Option.scala:121)
        at org.apache.spark.util.Utils$.localHostName(Utils.scala:941)
        at org.apache.spark.internal.config.package$.<init>(package.scala:204)
        at org.apache.spark.internal.config.package$.<clinit>(package.scala)
        at org.apache.spark.SparkConf.validateSettings(SparkConf.scala:546)
        at org.apache.spark.SparkContext.<init>(SparkContext.scala:373)
        at org.apache.spark.SparkContext$.getOrCreate(SparkContext.scala:2516)
        at org.apache.spark.sql.SparkSession$Builder$$anonfun$6.apply(SparkSession.scala:918)
        at org.apache.spark.sql.SparkSession$Builder$$anonfun$6.apply(SparkSession.scala:910)
        at scala.Option.getOrElse(Option.scala:121)
        at org.apache.spark.sql.SparkSession$Builder.getOrCreate(SparkSession.scala:910)
        at com.enmo.dbaas.util.MongoSparkSession$.get(MongoSparkSession.scala:25)
        at com.enmo.dbaas.util.MongoSparkSession$.getDefault(MongoSparkSession.scala:30)
        at com.enmo.dbaas.controller.ComputeTriggerController.tablespace(ComputeTriggerController.scala:116)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)

不知为什么日志没有记录这个`ERROR`，这个日志级别并不是`DEBUG`，但是找到错了就松了一口气。找到报错的方法：

private def findLocalInetAddress(): InetAddress = {
        val defaultIpOverride = System.getenv("SPARK_LOCAL_IP")
        if (defaultIpOverride != null) {
          InetAddress.getByName(defaultIpOverride)
        } else {
          val address = InetAddress.getLocalHost
          if (address.isLoopbackAddress) {
            // Address resolves to something like 127.0.1.1, which happens on Debian; try to find
            // a better address using the local network interfaces
            // getNetworkInterfaces returns ifs in reverse order compared to ifconfig output order
            // on unix-like system. On windows, it returns in index order.
            // It's more proper to pick ip address following system output order.
            val activeNetworkIFs = NetworkInterface.getNetworkInterfaces.asScala.toSeq
            val reOrderedNetworkIFs = if (isWindows) activeNetworkIFs else activeNetworkIFs.reverse
    
            for (ni <- reOrderedNetworkIFs) {
              val addresses = ni.getInetAddresses.asScala
                .filterNot(addr => addr.isLinkLocalAddress || addr.isLoopbackAddress).toSeq
              if (addresses.nonEmpty) {
                val addr = addresses.find(_.isInstanceOf[Inet4Address]).getOrElse(addresses.head)
                // because of Inet6Address.toHostName may add interface at the end if it knows about it
                val strippedAddress = InetAddress.getByAddress(addr.getAddress)
                // We've found an address that looks reasonable!
                logWarning("Your hostname, " + InetAddress.getLocalHost.getHostName + " resolves to" +
                  " a loopback address: " + address.getHostAddress + "; using " +
                  strippedAddress.getHostAddress + " instead (on interface " + ni.getName + ")")
                logWarning("Set SPARK_LOCAL_IP if you need to bind to another address")
                return strippedAddress
              }
            }
            logWarning("Your hostname, " + InetAddress.getLocalHost.getHostName + " resolves to" +
              " a loopback address: " + address.getHostAddress + ", but we couldn't find any" +
              " external IP address!")
            logWarning("Set SPARK_LOCAL_IP if you need to bind to another address")
          }
          address
        }
      }

原来是先从`SPARK_LOCAL_IP`环境变量找IP，再找hostname对应的IP。正常情况下，hostname会在`/etc/hosts`映射成`127.0.0.1`，但是这个主机的hostname被修改过，导致`hostname`对应的ip为空，所以才会报`java.net.UnknownHostException: dev: Name or service not known`。

在`/etc/hosts`加上主机名和ip的映射关系，重启后一切正常。

## 总结 ##

搜索过程中发现很多类似的错误，大部分都是具体到`org.apache.spark.internal.config.package$`某一个变量，以后遇到这种问题，用相同的解决思路应该能找打解决办法。

[70]: /images/20220514/4e52204946994574a097264635482ff1.png
[70 1]: /images/20220514/9dc3396d5880412b93124fbd578cff5f.png
[70 2]: /images/20220514/e0c97a99c68c4342ad4239476f9b6b51.png