Database Reference
In-Depth Information
Understanding the Apache Hadoop
daemons
Most of the Apache Hadoop clusters in production run Apache Hadoop 1.x
(MRv1—MapReduce Version 1). However, the new version of Apache Hadoop, 2.x
(MRv2—MapReduce Version 2), also referred to as
Yet Another Resource Negotiator
(
YARN
) is being adopted by many organizations actively. In this section, we shall go
through the daemons for both these versions.
Apache Hadoop 1.x (MRv1) consists of the following daemons:
• Namenode
• Secondary namenode
• Jobtracker
• Datanode
• Tasktracker
All the preceding daemons are Java services and run within their own JVM.
Apache Hadoop stores and processes data in a distributed fashion. To achieve this goal, Ha-
doop implements a master and slave model. The namenode and jobtracker daemons are
master daemons, whereas the datanode and tasktracker daemons are slave daemons.
