expvars prototype for suave.io

expvars.fsx

// Step 0. Boilerplate to get the paket.exe tool
 
open System
open System.IO

Environment.CurrentDirectory <- __SOURCE_DIRECTORY__
 
if (File.Exists "paket.exe") then
    File.Delete "paket.exe"
let url = "https://github.com/fsprojects/Paket/releases/download/3.18.2/paket.exe"
use wc = new Net.WebClient()
let tmp = Path.GetTempFileName()
wc.DownloadFile(url, tmp)
File.Move(tmp,Path.GetFileName url);;
 
// Step 1. Resolve and install the packages
 
#r "paket.exe"
 
Paket.Dependencies.Install """
source https://nuget.org/api/v2
nuget Suave
""";;
 
// Step 2. Use the packages
 
#r "packages/Suave/lib/net40/Suave.dll"
#r "System.Runtime.Serialization"
open Suave // always open suave
open Suave.Filters
open Suave.Operators
open Suave.Successful
open Suave.Json
open System.Runtime.Serialization
open System.Net


type RateCounter() = 
    let mutable lastTick = System.Environment.TickCount
    let mutable lastFrameRate = 0
    let mutable frameRate = 0
    let lockObj = new obj()
    let synchronized f v = lock lockObj (fun () -> f v)
    let inc v = 
            if System.Environment.TickCount - lastTick >= 1000 
            then
                lastFrameRate <- frameRate
                frameRate <- v
                lastTick <- System.Environment.TickCount
            else
                frameRate <- frameRate + v
            lastFrameRate
    

    member x.Inc v = synchronized inc v |> ignore
    member x.Get () = synchronized inc 0

    

let helloCounter = RateCounter() 

let hello (x : HttpContext) =
      helloCounter.Inc 1 
      OK "Hello World!" x

let _, server = startWebServerAsync defaultConfig hello

let client = new WebClient ()
let rec gen_load sleepMs = async{
    let! _ = client.AsyncDownloadString(new Uri("http://127.0.0.1:8083/"))
    do! Async.Sleep(sleepMs)
    return! gen_load(sleepMs) 
}
    

//startWebServer defaultConfig hello



let expvarsConfig = {defaultConfig with bindings = [ HttpBinding.mkSimple  Protocol.HTTP "0.0.0.0" 8000]}

let _, expvarsServer = startWebServerAsync expvarsConfig (path "/debug/vars" >=> fun ctx -> (OK (sprintf "{\"hellorps\":%d}" <| helloCounter.Get() ) ctx))

Async.Parallel [server; expvarsServer; gen_load(0)] |> Async.RunSynchronously |> ignore