Flink Sink parallelism = 1?

Question

I'm trying to understand how parallelism in Flink works. This doc https://ci.apache.org/projects/flink/flink-docs-release-1.9/concepts/programming-model.html seems to suggest that the sink has parallelism equal to 1. In my case, I'm writing to HBase in my sink - does this mean that there is only one task (thread?) which will be writing to HBase? Does it not get the global parallelism set for the application?

Answer 1

The sink gets the global parallelism. To reduce it on one operator, like in that example, requires explicitly changing the parallelism on that operator.

Answer 2

Does this mean there is only one task(thread) writing to HBase when parallelism equals to one?

Yes. Generally, the parallelism is the number of an operator's tasks that are running at the same time. By default it equals to the global parallelism you set.