Coordinator
Prototype for a process/library-based dora-rs implementation, instead of framework-based. The idea is that each operator is compiled as a separate executable. The dora-coordinator runtime is responsible for reading the dataflow descriptor file and launching the operators accordingly. The operators use a common library called dora-api, which implements the communication layer based on zenoh.
This approach has the following advantages:
- Less overhead
- No data transfer between a runtime and the operator
- The compiler can inline and optimize the full process
- More flexibility
- Operators can be sync or async
- They can decide how many threads and which execution model they use
- The OS ensures fair share of resources (e.g. CPU time) -> no need to cooperate with other operators
- Operators get all inputs immediately -> no need for input rules
- Keeping local state is easily possible
- Separate address spaces
- The operators are isolated from each other.
There are drawbacks too, for example:
- Less control
- Processes run independently -> need to cooperate with the runtime, e.g. on stop signals
- Operator migration is more difficult
- Operators are always isolated
- No way of using in-memory channels
- Local sockets and shared memory should be still possible