A series of obstactle courses as a way to compare how different languages and frameworks handle structured concurrency, including:

• loser cancellation
• resource management
• efficient thread utilization (i.e. reactive, non-blocking)
• explicit timeouts
• errors causing a race loss

A scenario server validates the implementations of 11 scenarios:

1. Race 2 concurrent requests

   GET /1
   

   The winner returns a 200 response with a body containing right

2. Race 2 concurrent requests, where one produces a connection error

   GET /2
   

   The winner returns a 200 response with a body containing right

3. Race 10,000 concurrent requests

   GET /3
   

   The winner returns a 200 response with a body containing right

4. Race 2 concurrent requests but 1 of them should have a 1 second timeout

   GET /4
   

   The winner returns a 200 response with a body containing right

5. Race 2 concurrent requests where a non-200 response is a loser

   GET /5
   

   The winner returns a 200 response with a body containing right

6. Race 3 concurrent requests where a non-200 response is a loser

   GET /6
   

   The winner returns a 200 response with a body containing right

7. Start a request, wait at least 3 seconds then start a second request (hedging)

   GET /7
   

   The winner returns a 200 response with a body containing right

8. Race 2 concurrent requests that "use" a resource which is obtained and released through other requests. The "use" request can return a non-20x request, in which case it is not a winner.

   GET /8?open
   GET /8?use=<id obtained from open request>
   GET /8?close=<id obtained from open request>
   

   The winner returns a 200 response with a body containing right

9. Make 10 concurrent requests where 5 return a 200 response with a letter

   GET /9
   

   When assembled in order of when they responded, form the "right" answer

10. This scenario validates that a computationally heavy task can be run in parallel to another task, and then cancelled.

    Part 1) Make a request and while the connection is open, perform something computationally heavy (e.g. repeated SHA calculation), then cancel the task when the connection closes

    GET /10?{some_id}
    

    Part 2) In parallel to Part 1, every 1 second, make a request with the current process load (0 to 1)

    GET /10?{same_id_as_part_1}={load}
    

    The request in Part 2 will respond with a 20x response if it looks like Part 1 was done correctly (in which case you can stop sending load values), otherwise it will respond with a 30x response if you should continue sending values, or with a 40x response if something has gone wrong.

11. This scenario validates that a race where all racers fail, is handled correctly. Race a request with another race of 2 requests.

    GET /11
    

    The winner returns a 200 response with a body containing right

The scenario server has a public container ghcr.io/jamesward/easyracer and if you contribute your client to this repo, use Testcontainers and include automated integration tests.

For local dev you can spin up the server via Docker:

docker run -it -p8080:8080 ghcr.io/jamesward/easyracer --debug

Source	Scenario Coverage	Author(s)	Notes
Scala 3 ZIO	11/11	James Ward
Scala 3 Ox	10/11	Adam Warski
Scala 3 Kyo	10/11	James Ward
Scala 3 Gears	10/11	Jack Leow
Scala 3 Akka Streams	10/11	Jack Leow
Kotlin Coroutines	10/11	Jack Leow
Kotlin Flow	10/11	Jack Leow
Kotlin Splitties	11/11	James Ward
Kotlin Arrow	11/11	James Ward
Java Loom	10/11	James Ward
Java Jox	11/11	James Ward
Rust Tokio	10/11	James Ward and Rust Developer Retreat Participants
C#	10/11	Jason De Lorme	Scenario 10: CPU Not Pegged
F# Reactive Extensions	10/11	Jack Leow
OCaml Lwt Cohttp	10/11	Puneeth Chaganti
OCaml Eio Cohttp	10/11	Puneeth Chaganti
Python AIOHTTP TaskGroup	9/11	James Ward Bruce Eckel	Needs Scenario 10 Impl
Python RxPy	10/11	Jack Leow
Go	10/11	Jack Leow
Go conc	10/11	Jack Leow
Swift Grand Central Dispatch	10/11	Jack Leow
Swift async/await	10/11	Jack Leow
Swift Combine	10/11	Jack Leow
Elm	10/11	Jack Leow
JavaScript	9/11	James Ward	Needs Scenario 10 Impl
Scala Cats Effects 3	9/11	Paul Snively	Needs Scenario 10 Impl
Python HTTPX Trio	8/11	James Ward	Needs Scenarios 3, 10
Python AIOHTTP	6/11	James Ward	Needs Scenarios 3, 4, 8, 10
Python HTTPX asyncio	2/11	James Ward	Needs Scenarios 3-10