Connection refused to Hadoop hdfs.

[ohonchar]

Through performing steps on tutorial https://radanalytics.io/examples/pyspark_hdfs_notebook . I've created instance with hadoop and configured hadoop single node as specified here https://hadoop.apache.org/docs/r2.7.1/hadoop-project-dist/hadoop-common/SingleCluster.html.
Forwarded ports 50070 and 8020.

Deployed Jupyter notebook http://base-notebook-ohonchar.10.19.47.76.nip.io/notebooks/PySpark_HDFS.ipynb (password: supersecret) in Openshift accordingly tutorial.

As a result I can access to web ui interface http://10.8.251.197:50070/ but unfortunately I can not access to hdfs://http://10.8.251.197:8020/user/nbuser/input. In Jupyter notebook it returns with an error "Connection refused".

edit by elmiko: removed sensitive info

[elmiko]

i have tested this and i am also receiving the same error. this is almost certainly an issue with how hdfs is setup. i think the best course of action is for us to review how we're instructing people to use a test hdfs and revise the instructions.

i have a feeling this would work on a system with a properly configured hdfs.

[elmiko]

i think the port in the notebook might be wrong as well, you can see the datanode address and port by visiting the web page created by the hdfs namenode. by default this is 50010, you might try that as well.

[elmiko]

i am able to access the hdfs store, but i see this error when reading the file:

Py4JJavaErrorTraceback (most recent call last)
<ipython-input-3-7ae5f9e1f57a> in <module>()
      1 import os
      2 text_file = spc.textFile("hdfs://%s:%d%s" % (hdfs_host, hdfs_port, os.path.join("/", hdfs_path)))
----> 3 counts = text_file.flatMap(lambda line: line.split(" "))              .map(lambda word: (word, 1))              .reduceByKey(lambda a, b: a + b)
      4 values = counts.collect()
      5 if len(values) > 20:

/opt/spark/python/pyspark/rdd.pyc in reduceByKey(self, func, numPartitions, partitionFunc)
   1606         [('a', 2), ('b', 1)]
   1607         """
-> 1608         return self.combineByKey(lambda x: x, func, func, numPartitions, partitionFunc)
   1609 
   1610     def reduceByKeyLocally(self, func):

/opt/spark/python/pyspark/rdd.pyc in combineByKey(self, createCombiner, mergeValue, mergeCombiners, numPartitions, partitionFunc)
   1832         """
   1833         if numPartitions is None:
-> 1834             numPartitions = self._defaultReducePartitions()
   1835 
   1836         serializer = self.ctx.serializer

/opt/spark/python/pyspark/rdd.pyc in _defaultReducePartitions(self)
   2242             return self.ctx.defaultParallelism
   2243         else:
-> 2244             return self.getNumPartitions()
   2245 
   2246     def lookup(self, key):

/opt/spark/python/pyspark/rdd.pyc in getNumPartitions(self)
   2438 
   2439     def getNumPartitions(self):
-> 2440         return self._prev_jrdd.partitions().size()
   2441 
   2442     @property

/opt/spark/python/lib/py4j-0.10.4-src.zip/py4j/java_gateway.py in __call__(self, *args)
   1131         answer = self.gateway_client.send_command(command)
   1132         return_value = get_return_value(
-> 1133             answer, self.gateway_client, self.target_id, self.name)
   1134 
   1135         for temp_arg in temp_args:

/opt/spark/python/lib/py4j-0.10.4-src.zip/py4j/protocol.py in get_return_value(answer, gateway_client, target_id, name)
    317                 raise Py4JJavaError(
    318                     "An error occurred while calling {0}{1}{2}.\n".
--> 319                     format(target_id, ".", name), value)
    320             else:
    321                 raise Py4JError(

Py4JJavaError: An error occurred while calling o21.partitions.
: java.io.EOFException: End of File Exception between local host is: "base-notebook-1-s5wwq/172.17.0.5"; destination host is: "10.0.1.114":50010; : java.io.EOFException; For more details see:  http://wiki.apache.org/hadoop/EOFException
	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.net.NetUtils.wrapWithMessage(NetUtils.java:792)
	at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:765)
	at org.apache.hadoop.ipc.Client.call(Client.java:1479)
	at org.apache.hadoop.ipc.Client.call(Client.java:1412)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
	at com.sun.proxy.$Proxy21.getFileInfo(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getFileInfo(ClientNamenodeProtocolTranslatorPB.java:771)
	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:191)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
	at com.sun.proxy.$Proxy22.getFileInfo(Unknown Source)
	at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:2108)
	at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1305)
	at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
	at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
	at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1317)
	at org.apache.hadoop.fs.Globber.getFileStatus(Globber.java:57)
	at org.apache.hadoop.fs.Globber.glob(Globber.java:252)
	at org.apache.hadoop.fs.FileSystem.globStatus(FileSystem.java:1676)
	at org.apache.hadoop.mapred.FileInputFormat.singleThreadedListStatus(FileInputFormat.java:259)
	at org.apache.hadoop.mapred.FileInputFormat.listStatus(FileInputFormat.java:229)
	at org.apache.hadoop.mapred.FileInputFormat.getSplits(FileInputFormat.java:315)
	at org.apache.spark.rdd.HadoopRDD.getPartitions(HadoopRDD.scala:199)
	at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:252)
	at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:250)
	at scala.Option.getOrElse(Option.scala:121)
	at org.apache.spark.rdd.RDD.partitions(RDD.scala:250)
	at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:35)
	at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:252)
	at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:250)
	at scala.Option.getOrElse(Option.scala:121)
	at org.apache.spark.rdd.RDD.partitions(RDD.scala:250)
	at org.apache.spark.api.java.JavaRDDLike$class.partitions(JavaRDDLike.scala:61)
	at org.apache.spark.api.java.AbstractJavaRDDLike.partitions(JavaRDDLike.scala:45)
	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 py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
	at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
	at py4j.Gateway.invoke(Gateway.java:280)
	at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
	at py4j.commands.CallCommand.execute(CallCommand.java:79)
	at py4j.GatewayConnection.run(GatewayConnection.java:214)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.EOFException
	at java.io.DataInputStream.readInt(DataInputStream.java:392)
	at org.apache.hadoop.ipc.Client$Connection.receiveRpcResponse(Client.java:1084)
	at org.apache.hadoop.ipc.Client$Connection.run(Client.java:979)

[elmiko]

ok, i got it working, but i had to do a couple things

1. set the etc/hadoop/core-site.xml config to this

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://10.0.1.114:9000</value>
    </property>
</configuration>

2. use 9000 as the connection port

in your case you will need to set the core-site.xml to this probably:

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://10.8.251.197:9000</value>
    </property>
</configuration>

and then use port 9000 to connect, although i'm guessing you could change that 8020 in the config file

[elmiko]

we need to revisit that tutorial and make it clearer. thanks for bringing this up!