hdfs Java api踩坑

1. 使用Java api上传到hdfs系统时报错：
   21/02/23 03:40:59 WARN blockmanagement.BlockPlacementPolicy: Failed to place enough replicas, still in need of 1 to reach 1 (unavailableStorages=[], storagePolicy=BlockStoragePolicy{HOT:7, storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}, newBlock=true) For more information, please enable DEBUG log level on org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy
   21/02/23 03:40:59 WARN protocol.BlockStoragePolicy: Failed to place enough replicas: expected size is 1 but only 0 storage types can be selected (replication=1, selected=[], unavailable=[DISK], removed=[DISK], policy=BlockStoragePolicy{HOT:7, storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]})
   21/02/23 03:40:59 WARN blockmanagement.BlockPlacementPolicy: Failed to place enough replicas, still in need of 1 to reach 1 (unavailableStorages=[DISK], storagePolicy=BlockStoragePolicy{HOT:7, storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}, newBlock=true) All required storage types are unavailable: unavailableStorages=[DISK], storagePolicy=BlockStoragePolicy{HOT:7, storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}
   21/02/23 03:40:59 INFO ipc.Server: IPC Server handler 7 on 8020, call org.apache.hadoop.hdfs.protocol.ClientProtocol.addBlock from 10.0.3.14:56564 Call#3 Retry#0
   java.io.IOException: File /hdfs-api/test0/hello.txt could only be replicated to 0 nodes instead of minReplication (=1). There are 1 datanode(s) running and 1 node(s) are excluded in this operation.
   at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1628)
   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getNewBlockTargets(FSNamesystem.java:3121)
   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:3045)
   at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:725)
   at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:493)
   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$1.run(Server.java:2213)
   at java.security.AccessController.doPrivileged(Native Method)
   at javax.security.auth.Subject.doAs(Subject.java:422)
   at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1746)
   at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2213)

经排查是一个datanode的50010端口未开放，开放之后解决此问题。

参考：
1.https://stackoverflow.com/questions/14288453/writing-to-hdfs-from-java-getting-could-only-be-replicated-to-0-nodes-instead
2.https://segmentfault.com/q/1010000016497552/a-1020000016505522#