Parallelism of a topology
Parallelism means the distribution of jobs on multiple nodes/instances where each instance can work independently and can contribute to the processing of data. Let's first look at the processes/components that are responsible for the parallelism of a Storm cluster.
Worker process
A Storm topology is executed across multiple supervisor nodes in the Storm cluster. Each of the nodes in the cluster can run one or more JVMs called worker processes, which are responsible for processing a part of the topology.
A worker process is specific to one of the specific topologies and can execute multiple components of that topology. If multiple topologies are being run at the same time, none of them will share any of the workers, thus providing some degree of isolation between topologies.
Executor
Within each worker process, there can be multiple threads executing parts of the topology. Each of these threads is called an executor. An executor can execute only one of the components...
