Storm Note arrangement (4): core concept and Verification of Storm-- parallelism and streaming grouping

[TOC]

Parallelism of Storm Core Concepts

Work

1 worker process executes a subset of 1 topology (Note: there will not be 1 worker for multiple topology services). A worker process starts one or more executor threads to execute a topology (spout or bolt). Therefore, a running topology is made up of one or more worker processes on multiple (possibly one) physical machines in the cluster.

Executor

Executor is a separate thread that the worker process starts.

Each executor will only run 1 or more (spout or bolt) task of 1 topology (Note: task can be 1 or more, storm defaults to 1 (spout or bolt) only 1 task,executor thread will call all task instances sequentially in each loop).

Task

Task is the execution unit that ultimately runs the code in spout or bolt (Note: 1 task is an instance of spout or bolt, and the executor thread calls the nextTuple or execute method of that task during execution). After topology starts, the number of task of 1 (spout or bolt) is fixed, but the number of executor threads used by this (spout or bolt) can be dynamically adjusted (for example, 1 executor thread can execute one or more task instances of that (spout or bolt)). This means that there is a condition for 1 (spout or bolt): # threads "+ userId +"+ userId +"