In this chapter, we discussed important Hadoop daemons and the ports on which they listen. Each daemon listens on a specific port and communicates with the respective daemons using a specific protocol. We looked at the ports for NameNode, DataNodes, and JobTracker and how they talk to each other.
Then we set up monitoring for each of the Hadoop nodes to enable host level checks such as disk quota, CPU usage, memory usage, and so on. In the upcoming chapters, we will talk about configuring checks for Hadoop services. In the next chapter, we will deal with Hadoop logging.
