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AsyncSteps intro

FutoIn AsyncSteps is a concept of asynchronous program flow coding in a way which closely mimics traditional synchronous threads.

The concept is clearly different from trivial Promise, async/await, or generic coroutines, but it matches and exceeds those in speed. In fact, it has a much lower theoretical flow switching overhead than required by bare metal coroutines with full register file dump & restore plus other maintenance work.

The FutoIn AsyncSteps concept was born when none of those were standardized. Also, it is implemented in bare metal languages like C++ and supports an ISO C11 binary interface. It’s the essential part which allows safe transfer of complex financial business logic to a scalable asynchronous runtime.

Overall features & goals:

  • Mimic “thread of execution”:
    • allow cancelling from outside,
    • cancel by timeout as a standard feature,
    • “atexit”-like cleanup actions.
  • Mimic “try-catch”:
    • clear scoping of inner blocks,
    • mimic “stack unwinding” on errors and cancels,
    • RAII-like cleanup on async stack unwinding,
    • support recovery actions in catch.
  • Mimic “worker pool”:
    • parallel execution of steps,
    • early cancel on error.
  • Mimic “thread local storage”:
    • per-instance state,
    • also shared within worker pool.
  • Mimic synchronization primitives:
    • Mutex - limit number of concurrent “threads” in critical section,
    • Throttle - limit number of critical section entries in period,
    • Limiter - merge of Mutex and Throttle.
  • Support loops:
    • generic loop with continue and break using optional labels,
    • repeat for specified number of times,
    • foreach over arrays, objects, sequences, and iterators.
  • Cross-technology exceptions and error info:
    • assumed to be passed over network,
    • error code - persistent string code,
    • error info - arbitrary human-readable string.
  • Integration with any external async wait approach:
    • including regular callbacks, Promise, and await,
    • support timeouts & cleanup handlers out-of-the-box.
  • Chain passing of “result->input” sequences:
    • explicit as.success() arguments are passed to the next step.
  • Integration with implementation-specific Futures and Promises:
    • acts as a regular step.
  • Memory Pool management for non-GC technologies:
    • allows fine control of memory limits per event loop instance,
    • removes heap synchronization overhead with around 30% boost in tests.
  • Designed for integration into foreign event loops and input/output reactors.

Specification

FTN12: FutoIn Async API is a single AsyncSteps specification.

Reference Implementations