Hadoop2.7.3: Cannot see DataNode/ResourceManager process after starting hdfs and yarn - macos

Question

I'm using mac and java version:
$java -version
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)
followed this link: https://dtflaneur.wordpress.com/2015/10/02/installing-hadoop-on-mac-osx-el-capitan/
I first brew install hadoop, config ssh connection and xml files as required, and
start-dfs.sh
start-yarn.sh
The screen output is like this:
$start-dfs.sh
17/05/06 09:58:32 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Starting namenodes on [localhost]
localhost: namenode running as process 74213. Stop it first.
localhost: starting datanode, logging to /usr/local/Cellar/hadoop/2.7.3/libexec/logs/hadoop-x-datanode-xdeMacBook-Pro.local.out
Starting secondary namenodes [0.0.0.0]
0.0.0.0: secondarynamenode running as process 74417. Stop it first.
17/05/06 09:58:39 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
$start-dfs.sh
17/05/06 09:58:32 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Starting namenodes on [localhost]
localhost: namenode running as process 74213. Stop it first.
localhost: starting datanode, logging to /usr/local/Cellar/hadoop/2.7.3/libexec/logs/hadoop-x-datanode-xdeMacBook-Pro.local.out
Starting secondary namenodes [0.0.0.0]
0.0.0.0: secondarynamenode running as process 74417. Stop it first.
17/05/06 09:58:39 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Then using jps I cannot see "DataNode" and "ResourceManager". I suppose DataNode is hdfs module and ResourceManager is yarn module:
$jps
74417 SecondaryNameNode
75120 Jps
74213 NameNode
74539 ResourceManager
74637 NodeManager
I can list hdfs files:
$hdfs dfs -ls /
17/05/06 09:58:59 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 1 items
drwxr-xr-x - x supergroup 0 2017-05-05 23:50 /user
But running the pi examples throws exception:
$hadoop jar /usr/local/Cellar/hadoop/2.7.3/libexec/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar pi 2 5
Number of Maps = 2
Samples per Map = 5
17/05/06 10:19:48 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
17/05/06 10:19:49 WARN hdfs.DFSClient: DataStreamer Exception
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /user/x/QuasiMonteCarlo_1494037188550_135794067/in/part0 could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation.
I wonder if I missed any configuation, how can I make sure that they run successfully, and how to check or trouble shoot possible failure reasons?
Thanks.

Answer 1

I am too in learning phase yet. This error comes when there is no datanode available to read/write.
You can check Resource Manager using this URL: http://localhost:50070
Is there any datanode running or not.
For trouble shooting you can check logs generated under installation directory of hadoop . If you can share that logs i can try to help.