A Throttled_rate_limiter combines a Token_bucket and a Throttle. Unlike a
Token_bucket jobs cannot consume variable numbers of tokens, but the number
of outstanding jobs is also limited to max_concurrent_jobs. Like a Throttlefinish_job must be called once, and only once when a job is completed.
val create_exn : now:Core_kernel.Time_ns.t ‑> burst_size:Core_kernel__.Import.int ‑> sustained_rate_per_sec:Core_kernel__.Import.float ‑> max_concurrent_jobs:Core_kernel__.Import.int ‑> tval try_start_job : t ‑> now:Core_kernel.Time_ns.t ‑> [ `Start | `Max_concurrent_jobs_running | `Unable_until_at_least of Core_kernel.Time_ns.t ]val finish_job : t ‑> now:Core_kernel.Time_ns.t ‑> Core_kernel__.Import.unit