Apache Mesos is an open source system for resource sharing across a cluster. It allows multiple frameworks to share a cluster by managing and scheduling resources. It is a cluster manager, which provides isolation using Linux containers, allowing multiple systems such as Hadoop, Spark, Kafka, Storm, and more to share a cluster safely. This is a master-slave based system using Zookeeper for configuration management. This way you can scalae up your Spark jobs to thousands of nodes. For a single master node Mesos cluster, the Spark master URL will be in the following form:

mesos://<hostname>:5050

The consequence of a Spark job submission by specifically using Mesos can be shown visually in the following figure:

In the preceding figure, where <hostname> is the hostname of the Mesos master server, and the port is defined as 5050, which is the default Mesos master port (this is configurable). If there are multiple Mesos master servers in a large-scale high availability Mesos cluster, then the Spark master URL would look like the following:

mesos://zk://<hostname>:2181

So, the election of the Mesos master server will be controlled by Zookeeper. The <hostname> will be the name of a host in the Zookeeper quorum. Also, the port number 2181 is the default master port for Zookeeper.