The parallelism of Storm

物理架构：一个nimbus， 数个supervisor

每个supervisor默认拥有4个slots，一个worker进程将占用一个slot，拥有独立的jvm

一个topology的config可以配置the number of workers

A worker process executes a subset of a topology, and runs in its own JVM.

An executor is a thread that is spawned by a worker process and runs within the worker’s JVM

A task performs the actual data processing and is run within its parent executor’s thread of execution.

executor数<=task数，topology一旦运行task数不变，executor数可以rebalance

ref：Understanding the Parallelism of a Storm Topology