So I installed Hadoop via Cloudera Manager cdh3u5 on CentOS 5. When I run cmd
hadoop fs -ls /
I expected to see the contents of hdfs://localhost.localdomain:8020/
However, it had returned the contents of file:///
Now, this goes without saying that I can access my hdfs:// through
hadoop fs -ls hdfs://localhost.localdomain:8020/
But when it came to installing other applications such as Accumulo, accumulo would automatically detect Hadoop Filesystem in file:///
Question is, has anyone ran into this issue and how did you resolve it?
I had a look at HDFS thrift server returns content of local FS, not HDFS , which was a similar issue, but did not solve this issue.
Also, I do not get this issue with Cloudera Manager cdh4.
By default, Hadoop is going to use local mode. You probably need to set fs.default.name to hdfs://localhost.localdomain:8020/ in $HADOOP_HOME/conf/core-site.xml.
To do this, you add this to core-site.xml:
<property>
<name>fs.default.name</name>
<value>hdfs://localhost.localdomain:8020/</value>
</property>
The reason why Accumulo is confused is because it's using the same default configuration to figure out where HDFS is... and it's defaulting to file://
We should specify data node data directory and name node meta data directory.
dfs.name.dir,
dfs.namenode.name.dir,
dfs.data.dir,
dfs.datanode.data.dir,
fs.default.name
in core-site.xml file and format name node.
To format HDFS Name Node:
hadoop namenode -format
Enter 'Yes' to confirm formatting name node. Restart HDFS service and deploy client configuration to access HDFS.
If you have already did the above steps. Ensure client configuration is deployed correctly and it points to the actual cluster endpoints.
Related
I am getting below error:
Diagnostics: org.apache.hadoop.hdfs.BlockMissingException: Could not obtain block: BP-467931813-10.3.20.155-1514489559979:blk_1073741991_1167 file=/user/oozie/share/lib/lib_20171228193421/oozie/hadoop-auth-2.7.2-amzn-2.jar
Failing this attempt. Failing the application.
Although I have set replication factor 3 for /user/oozie/share/lib/ directory. All the jars under this path are available on 3 datanode but few jars are missing.
Can any body suggest why this is happening and how to prevent this.
I was getting the same exception while trying to read a file from hdfs. The solution under the section "Clients use Hostnames when connecting to DataNodes" from this link worked for me:
https://hadoop.apache.org/docs/r2.7.2/hadoop-project-dist/hadoop-hdfs/HdfsMultihoming.html#Clients_use_Hostnames_when_connecting_to_DataNodes
I added this XML block to "hdfs-site.xml" and restarted the datanode and namenode servers:
<property>
<name>dfs.client.use.datanode.hostname</name>
<value>true</value>
<description>Whether clients should use datanode hostnames when
connecting to datanodes.
</description>
</property>
please check the file's owner in hdfs directory, I met this issue because the owner is "root", it got solved when I changed it to "your_user".
Got the same error when using Trino to connect to hive, I tried to connect HDFS from a Trino worker and found that port 9866 is not open on HDFS, opened the port on HDFS datenode and solved the problem. Related document: https://www.ibm.com/docs/en/spectrum-scale-bda?topic=requirements-firewall-recommendations-hdfs-transparency https://hadoop.apache.org/docs/r3.0.0/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml
I have a hadoop cluster on aws and I am trying to access it from outside the cluster through a hadoop client. I can successfully hdfs dfs -ls and see all contents but when I try to put or get a file I get this error:
Exception in thread "main" java.lang.NullPointerException
at org.apache.hadoop.fs.FsShell.displayError(FsShell.java:304)
at org.apache.hadoop.fs.FsShell.run(FsShell.java:289)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84)
at org.apache.hadoop.fs.FsShell.main(FsShell.java:340)
I have hadoop 2.6.0 installed in both my cluster and my local machine. I have copied the conf files of the cluster to the local machine and have these options in hdfs-site.xml (along with some other options).
<property>
<name>dfs.client.use.datanode.hostname</name>
<value>true</value>
</property>
<property>
<name>dfs.permissions.enable</name>
<value>false</value>
</property>
My core-site.xml contains a single property in both the cluster and the client:
<property>
<name>fs.defaultFS</name>
<value>hdfs://public-dns:9000</value>
<description>NameNode URI</description>
</property>
I found similar questions but wasn't able to find a solution to this.
How about you SSH into that machine?
I know this is a very bad idea but to get the work done, you can first copy that file on machine using scp and then SSH into that cluster/master and do hdfs dfs -put on that copied local file.
You can also automate this via a script but again, this is just to get the work done for now.
Wait for someone else to answer to know the proper way!
I had similar issue with my cluster when running hadoop fs -get and I could resolve it. Just check if all your data nodes are resolvable using FQDN(Fully Qualified Domain Name) from your local host. In my case nc command was successful using ip addresses for data nodes but not with host name.
run below command :
for i in cat /<host list file>; do nc -vz $i 50010; done
50010 is default datanode port
when you run any hadoop command it try to connect to data nodes using FQDN and thats where it gives this weird NPE.
Do below export and run your hadoop command
export HADOOP_ROOT_LOGGER=DEBUG,console
you will see this NPE comes when it is trying to connect to any datanode for data transfer.
I had a java code which was also doing hadoop fs -get using APIs and there ,exception was more clearer
java.lang.Exception: java.nio.channels.UnresolvedAddressException
Let me know if this helps you.
I have installed Hadoop in pseudo distributed mode on my laptop, OS is Ubuntu.
I have changed paths where hadoop will store its data (by default hadoop stores data in /tmp folder)
hdfs-site.xml file looks as below :
<property>
<name>dfs.data.dir</name>
<value>/HADOOP_CLUSTER_DATA/data</value>
</property>
Now whenever I restart machine and try to start hadoop cluster using start-all.sh script, data node never starts. I confirmed that data node is not start by checking logs and by using jps command.
Then I
Stopped cluster using stop-all.sh script.
Formatted HDFS using hadoop namenode -format command.
Started cluster using start-all.sh script.
Now everything works fine even if I stop and start cluster again. Problem occurs only when I restart machine and try to start the cluster.
Has anyone encountered similar problem?
Why this is happening and
How can we solve this problem?
By changing dfs.datanode.data.dir away from /tmp you indeed made the data (the blocks) survive across a reboot. However there is more to HDFS than just blocks. You need to make sure all the relevant dirs point away from /tmp, most notably dfs.namenode.name.dir (I can't tell what other dirs you have to change, it depends on your config, but the namenode dir is mandatory, could be also sufficient).
I would also recommend using a more recent Hadoop distribution. BTW, the 1.1 namenode dir setting is dfs.name.dir.
For those who use hadoop 2.0 or above versions config file names may be different.
As this answer points out, go to the /etc/hadoop directory of your hadoop installation.
Open the file hdfs-site.xml. This user configuration will override the default hadoop configurations, that are loaded by the java classloader before.
Add dfs.namenode.name.dir property and set a new namenode dir (default is file://${hadoop.tmp.dir}/dfs/name).
Do the same for dfs.datanode.data.dir property (default is file://${hadoop.tmp.dir}/dfs/data).
For example:
<property>
<name>dfs.namenode.name.dir</name>
<value>/Users/samuel/Documents/hadoop_data/name</value>
</property>
<property>
<name>dfs.datanode.data.dir</name>
<value>/Users/samuel/Documents/hadoop_data/data</value>
</property>
Other property where a tmp dir appears is dfs.namenode.checkpoint.dir. Its default value is: file://${hadoop.tmp.dir}/dfs/namesecondary.
If you want, you can easily also add this property:
<property>
<name>dfs.namenode.checkpoint.dir</name>
<value>/Users/samuel/Documents/hadoop_data/namesecondary</value>
</property>
Have installed cloudera cdh4 on 3 node cluster.Facing problem when trying to access the data in HDFS through slave nodes(Datanodes).
When I am trying to create the new folder in HDFS using
hadoop fs -mkdir Flume(Foldername)
command not able to put the data or create the folder in the hdfs of the cluster from either of the slaves,but working from the master node,also flume ,hive ,pig all other process are running in the slaves
(Datanodes)
Tried
restarting the cluster
namenode format
Still not working!!
Secondly When I am doing
hadoop fs -ls /
results are not of from the hdfs but from the current directory path of the slave node from where I am usin this command.
And how to check if hdfs is working and installed properly in slave nodes(Datanodes) in cluster apart from creating the directory in HDFS.
Could anybody help?
Please verify the property "fs.default.name" in the core-site.xml.
<property>
<name>fs.default.name</name>
<value>hdfs://namenode:9000</value>
</property>
Pseudomode Cluster:
Suppose first time I created a namenode on Machine "A" with name "Root1".
This will create a HDFS on tha machine.
Now i copy some file to HDFS using copyFromLocal and do some mapreduce.
Now i need to change some /conf files.
I'll change config file and to make them effective I formatted namenode with name "Root2".
If i browse the HDFS , it will be empty (means it will not contain those which copied earlier for "Root1").
If I want to see old file (for "Root1"), is there any way to switch to that HDFS or namenode (Root2 to Root1 ) ??
To be clear. Did you launch the another namenode on your machine ?
Type sudo jps in console or http://localhost:50070 in browser and check if you have more than one datanode. If there is just one node you lost your data from HDFS. If you have two namenodes you can check the filesystem in Internet browser on http://localhost:50070.
Here is instruction how to launch more than one datanode on one machine.