Commissioning an HDFS Application in the Linux Environment

Updated on 2024-10-23 GMT+08:00

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Scenario

The Hadoop distributed file system (HDFS) application can run in the Linux operating system (OS). After the application code has been developed, you can upload the jar packages to the Linux and run the application.

After an HDFS application is run, you can learn the application running conditions by viewing the running result or HDFS logs.

Prerequisite

When the client is installed:
- The HDFS client has been installed.
- When the host where the Linux OS runs is not a node of the cluster, you are required to set the mapping between the host name and IP address in the hosts file of the node where the client is installed. The host name must be correctly mapped to the IP address.
When the client is not installed:
- A JDK has been installed in the Linux environment. The version of the JDK must be consistent with that of the JDK used by IDEA to export the JAR package.
- When the host where the Linux OS runs is not a node of the cluster, you are required to set the mapping between the host name and IP address in the hosts file of the node where the Linux OS runs. The host name must be correctly mapped to the IP address.

Compiling and Running the Program When the Client is Installed

Go to the local root directory of the sample project, copy the required configuration file to the conf folder of the local project, and run the following command in Windows CLI to compress the package:

mvn -s "{maven_setting_path}" clean package
NOTE:
- In the preceding command, {maven_setting_path} is the path of the settings.xml file of the local Maven.
- After the package is successfully packed, obtain the JAR package, for example, HDFSTest-XXX.jar, from the target subdirectory in the root directory of the project. The name of the JAR package varies according to the actual package.
Upload the exported jarpackages to any directory in the running environment of the client, for example, /opt/client.
Configure the environment variables:

cd /opt/client

source bigdata_env
Specify a user to run the example. There are two ways to specify the user: add the environment variable HADOOP_USER_NAME and modify the code. If the code cannot be modified, run the following statement to add the environment variable:
```
export HADOOP_USER_NAME=test
```
NOTE:

The test user here is an example. To run the example code related to the Colocation operation, the user must be a member of the supergroup group.
Run the following commands to execute the jar packages.

hadoop jar HDFSTest-XXX.jar com.huawei.bigdata.hdfs.examples.HdfsExample

hadoop jar HDFSTest-XXX.jar com.huawei.bigdata.hdfs.examples.ColocationExample

NOTE:

When com.huawei.bigdata.hdfs.examples.ColocationExample is run, the HDFSparameter fs.defaultFS cannot be set to viewfs://ClusterX.

Compiling and Running an Application with the Client Not Installed

Go to the local root directory of the project, copy the required configuration file to the conf folder of the local project and run the following command in Windows CLI to compress the package:

mvn -s "{maven_setting_path}" clean package
NOTE:
- In the preceding command, {maven_setting_path} is the path of the settings.xml file of the local Maven.
- After the package is successfully packed, obtain the JAR package from the target subdirectory in the root directory of the project.
Upload the exported jar packages to any directory in the running environment of the Linux OS, for example, /opt/client.
Create a lib folder in the Linux operating environment directory (for example, /opt/client) and upload the required JAR packages. The lib folder contains all the JAR packages that the project depends on. For details, see section Preparing an Operating Environment.
Specify a user to run the example. There are two ways to specify the user: add the environment variable HADOOP_USER_NAME and modify the code. If the code cannot be modified, run the following statement to add the environment variable:
```
export HADOOP_USER_NAME=test
```
NOTE:

The test user here is an example. To run the example code related to the Colocation operation, the user must be a member of the supergroup group.
Run the following commands to execute the jar packages.

java -cp HDFSTest-XXX.jar:lib/* com.huawei.bigdata.hdfs.examples.HdfsExample

java -cp HDFSTest-XXX.jar:lib/* com.huawei.bigdata.hdfs.examples.ColocationExample

NOTE:

When com.huawei.bigdata.hdfs.examples.ColocationExample is run, the HDFSparameter fs.defaultFS cannot be set to viewfs://ClusterX.

Checking the Commissioning Result

Learn the application running conditions by viewing the running result.

The running result of the HDFS example application is shown as follows:

[root@192-168-32-144 client]#hadoop jar HDFSTest-XXX.jar com.huawei.bigdata.hdfs.examples.HdfsExample
WARNING: Use "yarn jar" to launch YARN applications.
17/10/26 19:11:44 INFO examples.HdfsExample: success to create path /user/hdfs-examples
17/10/26 19:11:44 INFO examples.HdfsExample: success to write.
17/10/26 19:11:45 INFO examples.HdfsExample: success to append.
17/10/26 19:11:45 INFO examples.HdfsExample: result is : hi, I am bigdata. It is successful if you can see me.I append this content.
17/10/26 19:11:45 INFO examples.HdfsExample: success to read.
17/10/26 19:11:45 INFO examples.HdfsExample: success to delete the file /user/hdfs-examples/test.txt
17/10/26 19:11:45 INFO examples.HdfsExample: success to delete path /user/hdfs-examples
17/10/26 19:11:45 INFO examples.HdfsExample: success to create path /user/hdfs-examples/hdfs_example_1
17/10/26 19:11:45 INFO examples.HdfsExample: success to create path /user/hdfs-examples/hdfs_example_0
17/10/26 19:11:45 INFO examples.HdfsExample: success to write.
17/10/26 19:11:45 INFO examples.HdfsExample: success to write.
17/10/26 19:11:46 INFO examples.HdfsExample: success to append.
17/10/26 19:11:46 INFO examples.HdfsExample: result is : hi, I am bigdata. It is successful if you can see me.I append this content.
17/10/26 19:11:46 INFO examples.HdfsExample: success to read.
17/10/26 19:11:46 INFO examples.HdfsExample: success to delete the file /user/hdfs-examples/hdfs_example_1/test.txt
17/10/26 19:11:46 INFO examples.HdfsExample: success to delete path /user/hdfs-examples/hdfs_example_1
17/10/26 19:11:46 INFO examples.HdfsExample: success to append.
17/10/26 19:11:46 INFO examples.HdfsExample: result is : hi, I am bigdata. It is successful if you can see me.I append this content.
17/10/26 19:11:46 INFO examples.HdfsExample: success to read.
17/10/26 19:11:46 INFO examples.HdfsExample: success to delete the file /user/hdfs-examples/hdfs_example_0/test.txt
17/10/26 19:11:46 INFO examples.HdfsExample: success to delete path /user/hdfs-examples/hdfs_example_0

The running result of the Colocation example application is shown as follows:

[root@192-168-32-144 client]#hadoop jar HDFSTest-XXX.jar com.huawei.bigdata.hdfs.examples.ColocationExample
WARNING: Use "yarn jar" to launch YARN applications.
17/10/26 19:12:38 INFO zookeeper.ZooKeeper: Client environment:zookeeper.version=xxx, built on 10/19/2017 04:21 GMT
17/10/26 19:12:38 INFO zookeeper.ZooKeeper: Client environment:host.name=192-168-32-144
17/10/26 19:12:38 INFO zookeeper.ZooKeeper: Client environment:java.version=1.8.0_144
17/10/26 19:12:38 INFO zookeeper.ZooKeeper: Client environment:java.vendor=Oracle Corporation
17/10/26 19:12:38 INFO zookeeper.ZooKeeper: Client environment:java.home=/opt/client/JDK/jdk1.8.0_144/jre
......
Create Group has finished.
Put file is running...
Put file has finished.
Delete file is running...
Delete file has finished.
Delete Group is running...
Delete Group has finished.
17/10/26 19:12:39 INFO zookeeper.ZooKeeper: Session: 0x13000074b7e4687f closed
17/10/26 19:12:39 INFO zookeeper.ClientCnxn: EventThread shut down for session: 0x13000074b7e4687f
17/10/26 19:12:39 INFO zookeeper.ZooKeeper: Session: 0x12000059699f69e1 closed
17/10/26 19:12:39 INFO zookeeper.ClientCnxn: EventThread shut down for session: 0x12000059699f69e1

Learn the application running conditions by viewing HDFS logs.
The NameNode logs of HDFS offer immediate visibility into application running conditions. You can adjust application programs based on the logs.

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