Multiparty Session Types (MPST) are a typing discipline that guarantees the absence of deadlocks and communication errors in concurrent and distributed systems. However, existing MPST frameworks do not support protocols with dynamic unbounded participants, and cannot express many common programming patterns that require the introduction of new participants into a protocol. This can pose a barrier for the adoption of MPST-based techniques to programming languages that favour the creation of new participants (processes, lightweight threads, etc) that communicate via message passing, such as Go or Erlang.

This paper proposes dynamically updatable unbounded multiparty session protocols, a new session types theory (DMst) that supports protocols with an unbounded number of fresh participants, whose communication structures are dynamically updatable during a protocol execution. We prove that DMst guarantees deadlock-freedom and liveness. We implement a toolchain, GoScr (Go-Scribble), which generates Go implementations from DMst, ensuring by construction, that the different participants will only perform I/O actions that comply with a given protocol specification. We evaluate our toolchain by (1) implementing representative parallel and concurrent algorithms from existing benchmarks, textbooks and literature; (2) showing that GoScr does not introduce significant overheads compared to a naive implementation, for computationally expensive benchmarks; and (3) building three realistic protocols (dynamic task delegation, recursive Domain Name System, and a parallel Min-Max strategy) in GoScr that could not be represented with previous theories of session types.