I have very basic questions on the Camunda Parallel Gateway outgoing fork execution behaviors.
How Camunda Parallel Gateway realizes parallel multi-exactions? How does it control the execution (threads) resource if one parallel gateway has many out going execution paths?
What is the Parallel Gateway “Exclusive” execution fashion? Simply means a sequential execution for multi-outgoing paths by a single thread? How to guaranty the execution continuity in error cases?
Workflow orchestration that happens in one transaction is always single-threaded. Now if tasks are handled externally (e.g. user tasks or external service tasks), then these can be performed in parallel. In addition, you can use asynchronous continuations and the exclusive flag to parallelize workflow orchestration in a single process instance. See details here: Transactions in Processes | docs.camunda.org.
However, workflow orchestration is not trivial to parallelize as it requires synchronization at some points in the workflow model and the workflow engine will enforce serialization at these points anyway (via optimistic locking and retries). So if you need parallelization, think about what you want to parallelize: The workflow orchestration or the task execution part? If it is the latter, consider running your tasks outside of the orchestrating transaction (e.g. external tasks).
I have trouble understanding these questions, but I have the feeling that the docs linked above should provide some perspective on these topics. I also recommend to read the entire “Transactions in Processes” section.