在windows主机用StreamingContext的checkpoint方法连接hdfs，抛如下异常：
Exception in thread "main" org.apache.hadoop.security.AccessControlException: Permission denied: user=yaj, access=WRITE, inode="/checkpoint":iotspark:supergroup:drwxr-xr-x
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:308)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:214)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:190)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkPermission(FSDirectory.java:1752)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkPermission(FSDirectory.java:1736)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkAncestorAccess(FSDirectory.java:1719)
at org.apache.hadoop.hdfs.server.namenode.FSDirMkdirOp.mkdirs(FSDirMkdirOp.java:69)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3872)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:984)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:634)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2217)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2213)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1758)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2213)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:73)
at org.apache.hadoop.hdfs.DFSClient.primitiveMkdir(DFSClient.java:3010)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:2978)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1047)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1043)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirsInternal(DistributedFileSystem.java:1061)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSystem.java:1036)
at org.apache.hadoop.fs.FileSystem.mkdirs(FileSystem.java:1877)
at org.apache.spark.SparkContext$$anonfun$setCheckpointDir$2.apply(SparkContext.scala:2316)
at org.apache.spark.SparkContext$$anonfun$setCheckpointDir$2.apply(SparkContext.scala:2313)
at scala.Option.map(Option.scala:146)
at org.apache.spark.SparkContext.setCheckpointDir(SparkContext.scala:2313)
at org.apache.spark.streaming.StreamingContext.checkpoint(StreamingContext.scala:242)
at com.spark.sunny.sparkstreaming.UpdateStateByKeyWordCount$.main(UpdateStateByKeyWordCount.scala:19)
at com.spark.sunny.sparkstreaming.UpdateStateByKeyWordCount.main(UpdateStateByKeyWordCount.scala)
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.AccessControlException): Permission denied: user=yaj, access=WRITE, inode="/checkpoint":iotspark:supergroup:drwxr-xr-x
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:308)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:214)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:190)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkPermission(FSDirectory.java:1752)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkPermission(FSDirectory.java:1736)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkAncestorAccess(FSDirectory.java:1719)
at org.apache.hadoop.hdfs.server.namenode.FSDirMkdirOp.mkdirs(FSDirMkdirOp.java:69)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3872)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:984)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:634)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2217)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2213)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1758)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2213)
at org.apache.hadoop.ipc.Client.call(Client.java:1476)
at org.apache.hadoop.ipc.Client.call(Client.java:1407)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy14.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.mkdirs(ClientNamenodeProtocolTranslatorPB.java:558)
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.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy15.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.primitiveMkdir(DFSClient.java:3008)
... 14 more
代码片段如下：
val conf = new SparkConf().setAppName("WordCount").setMaster("local[4]")
val ssc = new StreamingContext(conf, Seconds(1))
ssc.checkpoint("hdfs://iotsparkmaster:9000/checkpoint")
从中很容易看出是因为当前执行Spark Application的用户没有Hdfs“/user”目录的写入权限。这个问题其实无论是在Windows下还是Linux下提交Spark Application都经常会遇到。常见的解决方法有以下几种。
关闭Hdfs的安全检查（permission checking）：将hdfs-xml中 dfs.permissions 属性的值设置为 false 。但是这种方法的弊端是会导致Hdfs系统中所有的安全特性都被禁用，使Hdfs的安全性降低。
Hdfs的用户权限是与本地文件系统的用户权限绑定在一起的，根据错误中的
Permission denied: user=yaj, access=WRITE, inode="/checkpoint":iotspark:supergroup:drwxr-xr-x
我们可以发现，Hdfs中的/user目录是属于supergroup组里的root用户的。因此我们可以想到用两种方法解决这个问题：
修改执行操作的用户为该目录所属的用户。但是这种方法的弊端在于，与Hdfs进行交互的用户可能有很多，这会导致经常修改执行类似操作的用户。
因此，个人推荐使用第三种方法：
如果是Linux环境，将执行操作的用户添加到supergroup用户组。
groupadd supergroup
usermod -a -G supergroup yaj
如果是Windows用户，在hdfs namenode所在机器添加新用户，用户名为执行操作的Windows用户名，然后将此用户添加到supergroup用户组。
adduser yaj
groupadd supergroup
usermod -a -G supergroup yaj
如图：
image.png
这样，以后每次执行类似操作可以将文件写入Hdfs中属于yaj用户的目录内，而不会出现上面的Exception。