Hadoop 面试题与答案

问题 16. What is WebDAV in Hadoop?

WebDAV is a set of extension to HTTP which is used to support editing and uploading files. On most operating system WebDAV shares can be mounted as filesystems, so it is possible to access HDFS as a standard filesystem by exposing HDFS over WebDAV.

问题 17. What is Sqoop in Hadoop?

Sqoop is a tool used to transfer data between the Relational Database Management System (RDBMS) and Hadoop HDFS. By using Sqoop, you can transfer data from RDBMS like MySQL or Oracle into HDFS as well as exporting data from HDFS file to RDBMS.

问题 18. What are the functionalities of JobTracker?

These are the main tasks of JobTracker:

• To accept jobs from the client.
• To communicate with the NameNode to determine the location of the data.
• To locate TaskTracker Nodes with available slots.
• To submit the work to the chosen TaskTracker node and monitors the progress of each task.

问题 19. Define TaskTracker. What is TaskTracker in Hadoop?

TaskTracker is a node in the cluster that accepts tasks like MapReduce and Shuffle operations from a JobTracker.

问题 20. What is Map/Reduce job in Hadoop?

Map/Reduce job is a programming paradigm which is used to allow massive scalability across the thousands of server.

MapReduce refers to two different and distinct tasks that Hadoop performs. In the first step maps jobs which takes the set of data and converts it into another set of data and in the second step, Reduce job. It takes the output from the map as input and compresses those data tuples into the smaller set of tuples.