Difference between job, task and subtask in flink

Question

I'm new to flink and try to understand:

1. job
2. task
3. subtask

I searched in the docs but still did not get it. What's the main diffence between them?

Answer 1

Tasks and sub-tasks are explained here -- https://ci.apache.org/projects/flink/flink-docs-release-1.7/concepts/runtime.html#tasks-and-operator-chains:

A task is an abstraction representing a chain of operators that could be executed in a single thread. Something like a keyBy (which causes a network shuffle to partition the stream by some key) or a change in the parallelism of the pipeline will break the chaining and force operators into separate tasks. In the diagram above, the application has three tasks.

A subtask is one parallel slice of a task. This is the schedulable, runable unit of execution. In the diagram above, the application is to be run with a parallelism of two for the source/map and keyBy/Window/apply tasks, and a parallelism of one for the sink -- resulting in a total of 5 subtasks.

A job is a running instance of an application. Clients submit jobs to the jobmanager, which slices them into subtasks and schedules those subtasks for execution by the taskmanagers.