Can anyone help me out with this?

In short, I'm doing a HTTP POST with a handler along the lines of:
```
fun ((resp : Cohttp_async.Response.t)
    , (body : Cohttp_async.Body.t)) : unit Or_error.t ->
     let r : string Async.Pipe.Reader.t = Cohttp_async.Body.to_pipe body in
     let _ =
      Async.Pipe.iter
        r
        ~continue_on_error:true
        ~f:(fun s -> Async.return (printf "%s" s)) in
      (Ok () : unit Or_error.t)

```

Each time I invoke the program I get, more or less output (very
occasionally none) but never all of it. The response header says it's
"fixed  2700816" and indeed, if I replace the code above with
```
fun ((resp : Cohttp_async.Response.t)
    , (body : Cohttp_async.Body.t)) : unit Or_error.t ->
  let r : string Async.Pipe.Reader.t = Cohttp_async.Body.to_pipe body in
  let n : int Deferred.t =
    Async.Pipe.fold
      r
      ~init:0
      ~f:(fun acc s ->
            printf "acc : %d\n" acc; Async.return (acc + String.length s)
          ) in
  let _ : unit Deferred.t = n  >>| fun n -> printf "Chars read : %d" n in
  (Ok () : unit Or_error.t)

 ```
then (for example), on the first run I might see
```
acc : 0
acc : 1118
acc : 7503
acc : 8780

```

and then on the second run I might see
```
acc : 0
acc : 1118
acc : 4949

```
but never have I seen "Chars read : 2700816".

I've tried a bunch of different things:

  - `Pipe.read_all`:
     ```
       let _ =
         Async.Pipe.read_all r >>|
         fun q -> Queue.iter q ~f:(fun s -> printf "%s" s) in
       ...

     ```
     No output.

  - `Pipe.drain_and_count`:
    ```
      let _ =
        Async.Pipe.drain_and_count r >>|
        fun n -> printf "Count %d\n" n in
      ...

    ```
    No output.

  - `Pipe.to_list`:
     ```
     let _ =
       Async.Pipe.to_list r >>|
       fun l -> printf "%s" (String.concat ~sep:"" l) in
     ...

     ```
     No output.

Also tried the obvious:

  - `Cohttp_async.Body.to_string`:
    ```
      let s = Cohttp_async.Body.to_string body in
      let _ = s >>| fun  s -> printf "%s" s in
      ...

    ```
    No output.

I'm new to this and obviously missing something fundamental :) Is there a
kind soul out there who can give me a hint on how to proceed please?

Thanks!

-- 
Shayne Fletcher