Sample of polling reader of EventStore.ClientAPI in F#

EventStore.fs

// https://github.com/fsprojects/FSharp.Control.AsyncSeq
// RetryPolicy from https://github.com/jet/kafunk/blob/master/src/kafunk/Utility/Faults.fs#L89

/// Returns an Async computation which evaluates the input computation until the specified condition is met
/// with delays between attempts dictated by the specified retry policy.
let pollUntil (rp:RetryPolicy) (condition:'a -> bool) (a:Async<'a>) : Async<'a option> =
  (AsyncSeq.replicateInfiniteAsync a, RetryPolicy.delayStream rp)
  ||> AsyncSeq.interleaveChoice 
  |> AsyncSeq.tryPick (function Choice1Of2 a when condition a -> Some a | _ -> None)
  
// EventStore client

type Conn = string
type Position = int64
type Event = string

let readBatch (c:Conn) (p:Position) : Async<Event[] * Position> = failwith "TODO"

let stream (c:Conn) (p:Position) (rp:RetryPolicy) : AsyncSeq<Event[]> =
  p |> AsyncSeq.unfoldAsync (readBatch c >> pollUntil rp (fun (es,_) -> es.Length > 0))