if I want to implement the bulkhead pattern in kotlin, with an old-fashioned blocking http client (OkHttp/feign), what is an idiomatic way to do it in kotlin? A channel with a coroutinecontext backed by a fixed threadpool and ThreadPoolExecutor.AbortPolicy() ?

I'm not familiar with bulkhead but if you want to limit the threads used to handle the work then a FixedThreadPool would be the way to go imo

I want extra work to be rejected when the thread pool is empty (after queueing for a thread to run on with a configurable timeout)

You...want work to be thrown away when your thread pool has no work to do?

Other way around. Sounds like they want work to be thrown away when they don't have any open threads to do it.

I agree that's likely the intention, but I can't assume, so that's why I asked

I would use a number of coroutines equal to the number of threads you want, with a shared Channel of tasks that has a maximum capacity. Then offer tasks to the channel and loop it on the workers.

I think in coroutines you would rely on normal backpressure and use a timeout to detect too much work