When setting up a standalone Spark cluster, what should the "master" variable point to?

The "master" variable in a standalone Spark cluster should point to "spark://host:port" because this specific format is designed to allow Spark to communicate with the standalone cluster manager. In a standalone mode, the Spark master is responsible for resource management, allocating resources to the Spark applications running on the cluster.

By using the "spark://" prefix followed by the host and port, it directly indicates that Spark is managing the cluster itself without needing to rely on another cluster management system like Hadoop or Mesos. This ensures that Spark can efficiently manage the scheduling and execution of applications running in that cluster environment.

The other options refer to different resource managers or architectures. For example, "hadoop://host:port" is used for connecting to a Hadoop cluster's NameNode, while "mesos://host:port" connects to a Mesos cluster, which manages resources differently. The "cluster://" format is not standard for Spark, indicating it’s not applicable in this context. Thus, the correct designation for setting up a standalone Spark cluster is "spark://host:port," ensuring proper configuration and communication.