Hadoop Server

In the context of Hadoop, the term “Hadoop server” typically refers to a machine or node within a Hadoop cluster that is responsible for running various Hadoop services and processes. Hadoop is a distributed computing framework that allows the processing and storage of large datasets across a cluster of machines. Each machine in the cluster can function as a server to provide specific Hadoop services.

Here are some of the key components and roles that Hadoop servers play within a Hadoop cluster:

1. NameNode: The NameNode is a critical server in Hadoop’s HDFS (Hadoop Distributed File System). It manages the metadata and namespace of the file system, keeping track of where data is stored on DataNodes within the cluster.

2. DataNode: DataNodes are responsible for storing the actual data blocks of files in HDFS. They communicate with the NameNode to report the status of data blocks and replicate data for fault tolerance.

3. ResourceManager: In the context of Apache Hadoop’s YARN (Yet Another Resource Negotiator) resource management framework, ResourceManager is responsible for allocating cluster resources and managing the execution of MapReduce jobs and other applications.

4. NodeManager: NodeManagers run on each machine in the cluster and are responsible for monitoring resource usage and managing containers where application tasks (e.g., MapReduce tasks) run.

5. JobTracker (in Hadoop 1.x): In older versions of Hadoop (1.x), the JobTracker was responsible for managing and scheduling MapReduce jobs in the cluster.

6. HistoryServer: The HistoryServer, also known as the JobHistoryServer, is responsible for serving job history logs, allowing users to view historical information about completed jobs.

7. Hive Metastore: In the context of Hive, a data warehousing and SQL-like querying tool for Hadoop, the Hive Metastore server manages metadata about Hive tables and partitions.

8. HBase Master: In HBase, the HBase Master server manages and coordinates the distributed NoSQL database. It handles tasks such as region assignment and server failover.

9. ZooKeeper Servers: While not specific to Hadoop itself, ZooKeeper servers are often used for coordination and management within a Hadoop cluster, helping to maintain distributed state information.

10. Edge Node (Gateway Node): Edge nodes are not typically part of the core cluster but serve as interfaces for users and applications to interact with the Hadoop cluster. They may host client utilities, web interfaces, and application-specific services.