Format with Fantomas, and add MIT licence

.editorconfig

@@ -0,0 +1,13 @@
+root = true
+
+[*.fs]
+fsharp_space_before_uppercase_invocation=true
+fsharp_space_before_member=true
+fsharp_space_before_parameter=true
+fsharp_space_before_colon=true
+fsharp_space_before_semicolon=true
+fsharp_multiline_block_brackets_on_same_column=true
+fsharp_newline_between_type_definition_and_members=true
+fsharp_keep_if_then_in_same_line=true
+fsharp_align_function_signature_to_indentation=true
+fsharp_alternative_long_member_definitions=true

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Patrick Stevens
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

PulsingServer/ExternalInfoProvider.fs

@@ -11,9 +11,7 @@ type private ExternalInfoProviderMessage<'info> =
 
 /// An entity which periodically pulls information from some external source
 /// and pushes it out to a collection of ServerAgents.
-type ExternalInfoProvider<'info> =
+type ExternalInfoProvider<'info> = private ExternalInfoProvider of MailboxProcessor<ExternalInfoProviderMessage<'info>>
-    private
-    | ExternalInfoProvider of MailboxProcessor<ExternalInfoProviderMessage<'info>>
 
 [<RequireQualifiedAccess>]
 module ExternalInfoProvider =
@@ -29,14 +27,18 @@ module ExternalInfoProvider =
         (receivers : ServerAgent<'info> array)
         : Async<ExternalInfoProvider<'info>>
         =
-        let rec loop (info : 'info option) (receivers : ServerAgent<'info> array) (mailbox : MailboxProcessor<ExternalInfoProviderMessage<'info>>) =
+        let rec loop
+            (info : 'info option)
+            (receivers : ServerAgent<'info> array)
+            (mailbox : MailboxProcessor<ExternalInfoProviderMessage<'info>>)
+            =
             async {
                 match! mailbox.Receive () with
                 | Get (channel, timeout) ->
                     let! newInfo = get
+
                     match info with
-                    | Some info when newInfo = info ->
+                    | Some info when newInfo = info -> ()
-                        ()
                     | _ ->
                         do!
                             receivers
@@ -46,8 +48,8 @@ module ExternalInfoProvider =
 
                     match channel with
                     | None -> ()
-                    | Some channel ->
+                    | Some channel -> channel.Reply ()
-                        channel.Reply ()
+
                     do! sleep (TimeSpan.FromMilliseconds (float timeout))
                     // There's a small inaccuracy here. We actually will wait until the end
                     // of a timeout cycle before we can process any new consumers. What we
@@ -63,11 +65,11 @@ module ExternalInfoProvider =
             }
 
         async {
-            let mailbox = MailboxProcessor.Start (loop None receivers)
+            let mailbox =
+                MailboxProcessor.Start (loop None receivers)
+
             do! mailbox.PostAndAsyncReply (fun channel -> Get (Some channel, timer))
-            return
+            return mailbox |> ExternalInfoProvider
-                mailbox
-                |> ExternalInfoProvider
         }
 
     /// Replace the collection of ServerAgents this ExternalInfoProvider is hooked up to.

PulsingServer/ServerAgent.fs

@@ -4,7 +4,7 @@ type private ServerAgentMessage<'info> =
     | Read of AsyncReplyChannel<unit> * ('info -> unit)
     | Write of AsyncReplyChannel<unit> * 'info
 
-type ServerAgent<'info> = private | ServerAgent of MailboxProcessor<ServerAgentMessage<'info>>
+type ServerAgent<'info> = private ServerAgent of MailboxProcessor<ServerAgentMessage<'info>>
 
 [<RequireQualifiedAccess>]
 module ServerAgent =
@@ -39,7 +39,10 @@ module ServerAgent =
     /// the async returns once the ServerAgent has finished responding.
     let giveNextResponse<'info> (ServerAgent agent) : Async<'info> =
         let mutable answer = Unchecked.defaultof<'info>
-        let result = agent.PostAndAsyncReply (fun channel -> Read (channel, fun info -> answer <- info))
+
+        let result =
+            agent.PostAndAsyncReply (fun channel -> Read (channel, (fun info -> answer <- info)))
+
         async {
             do! result
             return answer

SampleApplication/Program.fs

@@ -13,11 +13,9 @@ open Microsoft.Extensions.Logging
 
 module Program =
     let createHostBuilder args =
-        Host.CreateDefaultBuilder(args)
+        Host
-            .ConfigureWebHostDefaults(fun webBuilder ->
+            .CreateDefaultBuilder(args)
-                webBuilder.UseStartup<Startup>()
+            .ConfigureWebHostDefaults(fun webBuilder -> webBuilder.UseStartup<Startup> () |> ignore)
-                |> ignore
-            )
 
     [<EntryPoint>]
     let main args =

SampleApplication/Startup.fs

@@ -46,22 +46,35 @@ type Startup() =
 
     let client = new WebClient ()
 
-    let servers = Array.init 2 (fun _ -> ServerAgent.make (Some { Hour = 0uy ; Minute = 0uy ; Second = 0uy }))
+    let servers =
+        Array.init
+            2
+            (fun _ ->
+                ServerAgent.make (
+                    Some
+                        {
+                            Hour = 0uy
+                            Minute = 0uy
+                            Second = 0uy
+                        }
+                ))
 
     /// Convert an input byte to the integer digit it is.
     /// For example, ord('0') will match to Char(0).
     let (|Char|_|) (b : byte) : byte option =
-        if byte '0' <= b && b <= byte '9' then
+        if byte '0' <= b && b <= byte '9' then Some (b - byte '0') else None
-            Some (b - byte '0')
-        else None
 
     /// Extremely rough-and-ready function to get a time out of a stream which contains
     /// text.
     /// We expect the time to be expressed as hh:mm:ss
     /// and we do not bother our pretty little heads with Unicode issues.
-    let parseDateInner (buffer : byte array) (s : Stream) (state : State) : Async<ParseOutput> = async {
+    let parseDateInner (buffer : byte array) (s : Stream) (state : State) : Async<ParseOutput> =
+        async {
             let! written = s.ReadAsync (buffer, 0, 1) |> Async.AwaitTask
-        if written = 0 then return StreamEnded else
+
+            if written = 0 then
+                return StreamEnded
+            else
 
                 match state with
                 | Waiting ->
@@ -94,18 +107,27 @@ type Startup() =
                     | _ -> return State Waiting
                 | ParsedSecondFirstDigit (hour, min, sec) ->
                     match buffer.[0] with
-            | Char b -> return Complete { Hour = hour ; Minute = min ; Second = 10uy * sec + b }
+                    | Char b ->
+                        return
+                            Complete
+                                {
+                                    Hour = hour
+                                    Minute = min
+                                    Second = 10uy * sec + b
+                                }
                     | _ -> return State Waiting
         }
 
-    let parseDate (stream : Stream) : Async<Date option> = async {
+    let parseDate (stream : Stream) : Async<Date option> =
+        async {
             let buffer = [| 0uy |]
-        let rec go (state : State) = async {
+
+            let rec go (state : State) =
+                async {
                     match! parseDateInner buffer stream state with
                     | StreamEnded -> return None
                     | Complete d -> return Some d
-            | State state ->
+                    | State state -> return! go state
-                return! go state
                 }
 
             return! go State.Waiting
@@ -115,12 +137,15 @@ type Startup() =
         async {
             // Note: there is absolutely no error handling here at all.
             // Obviously that would be desirable.
-            let result = client.OpenRead (Uri "insert your URL here")
+            let result =
+                client.OpenRead (Uri "https://www.timeanddate.com/worldclock/uk")
+
             return! parseDate result
         }
 
     // Note that we haven't kicked this off yet - it's still an Async
-    let pulses = ExternalInfoProvider.make Async.Sleep update 500<ms> servers
+    let pulses =
+        ExternalInfoProvider.make Async.Sleep update 500<ms> servers
 
     // This method gets called by the runtime. Use this method to add services to the container.
     // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
@@ -132,20 +157,29 @@ type Startup() =
         if env.IsDevelopment () then
             app.UseDeveloperExceptionPage () |> ignore
 
-        app.UseRouting()
+        app
+            .UseRouting()
             .UseEndpoints(fun endpoints ->
-                endpoints.MapGet("/", fun context ->
+                endpoints.MapGet (
+                    "/",
+                    fun context ->
                         async {
                             let! answer = ServerAgent.giveNextResponse servers.[0]
+
                             match answer with
-                        | None -> do! context.Response.WriteAsync("Oh noes") |> Async.AwaitTask
+                            | None ->
+                                do!
+                                    context.Response.WriteAsync ("Oh noes")
+                                    |> Async.AwaitTask
                             | Some date ->
-                            do! context.Response.WriteAsync(sprintf "%i:%i:%i" date.Hour date.Minute date.Second) |> Async.AwaitTask
+                                do!
+                                    context.Response.WriteAsync (sprintf "%i:%i:%i" date.Hour date.Minute date.Second)
+                                    |> Async.AwaitTask
+
                             return ()
                         }
                         |> Async.StartAsTask
                         :> Task
                 )
-                |> ignore
+                |> ignore)
-            )
         |> ignore

Test/PropertyBasedTests.fs

@@ -1,36 +0,0 @@
-namespace PulsingServer.Test
-
-open PulsingServer
-open NUnit.Framework
-open FsUnitTyped
-
-type AgentIndex = AgentIndex of int
-type ReadIndex = ReadIndex of int
-
-type Action<'info> =
-    | ChangeData of 'info
-    | BeginRead of AgentIndex
-    | AwaitRead of ReadIndex
-
-[<TestFixture>]
-module TestProperties =
-
-    let executeAction
-        (ext : ExternalInfoProvider<'info>)
-        (agents : ServerAgent<'info> array)
-        ((readNumber : int), (awaitingRead : Map<ReadIndex, Async<'info>>))
-        (action : Action<'info>)
-        =
-        match action with
-        | BeginRead (AgentIndex i) ->
-            let mutable answer = None
-            let result = ServerAgent.giveNextResponse (fun resp -> answer <- Some resp) agents.[i]
-            let output =
-                async {
-                    do! result
-                    return Option.get answer
-                }
-            ext, agents, (readNumber + 1, Map.add (ReadIndex readNumber) output awaitingRead)
-        | AwaitRead index ->
-            awaitingRead.[index]
-            |> Async.RunSynchronously

Test/TestServer.fs

@@ -17,14 +17,19 @@ module TestPulsingServer =
         let mutable info = "original info"
         let count = ref 0
 
-        let getInfo = async {
+        let getInfo =
-            System.Threading.Interlocked.Increment count |> ignore
+            async {
+                System.Threading.Interlocked.Increment count
+                |> ignore
+
                 let info = lock info (fun () -> sprintf "%s" info)
                 return info
             }
+
         let dontSleep (_ : TimeSpan) = async { return () }
 
-        let infoProvider = ExternalInfoProvider.make dontSleep getInfo 10<ms> [| responder1 ; responder2 |]
+        let infoProvider =
+            ExternalInfoProvider.make dontSleep getInfo 10<ms> [| responder1 ; responder2 |]
 
         // We're not getting new info, because we didn't await the construction of ExternalInfoProvider
         count.Value |> shouldEqual 0
@@ -32,30 +37,28 @@ module TestPulsingServer =
         // The two responders are ready, but have not received anything yet.
         do
             let response = ServerAgent.giveNextResponse responder1
+
             response
             |> Async.RunSynchronously
             |> shouldEqual "hi"
 
         // Now start off the ExternalInfoProvider!
-        let _ =
+        let _ = infoProvider |> Async.RunSynchronously
-            infoProvider
-            |> Async.RunSynchronously
 
         // Now we have definitely started pinging...
         count.Value |> shouldBeGreaterThan 0
 
-        // ... and at some point soon, the first responder will act on the info it receives.
+        // The two responders are ready, but have not received anything yet.
         do
             let response = ServerAgent.giveNextResponse responder1
+
             response
             |> Async.RunSynchronously
             |> shouldEqual "original info"
 
         // Update the info. responder1 is not going to fail on the `received` check, because that
         // was one-shot.
-        lock info (fun () ->
+        lock info (fun () -> info <- "new info!")
-            info <- "new info!"
-        )
 
         // Get responder2 ready to act in a couple of different ways.
         let response2 = ServerAgent.giveNextResponse responder2
@@ -69,6 +72,7 @@ module TestPulsingServer =
             // By design, we can't distinguish between these two cases.
             (info = "new info!" || info = "original info")
             |> shouldEqual true
+
         response2'
         |> Async.RunSynchronously
         |> fun info ->
@@ -78,16 +82,23 @@ module TestPulsingServer =
 
         // Eventually, responder2 does pick up the new info.
         let rec go () =
-            let response = ServerAgent.giveNextResponse responder2 |> Async.RunSynchronously
+            let response =
-            if response <> "new info!" then go ()
+                ServerAgent.giveNextResponse responder2
+                |> Async.RunSynchronously
+
+            if response <> "new info!" then
+                go ()
+
         go ()
 
     [<TestCase(10000, 1)>]
     [<TestCase(10000, 3)>]
     let ``Stress test`` (n : int, queues : int) =
-        let responders = Array.init queues (fun _ -> ServerAgent.make "uninitialised")
+        let responders =
+            Array.init queues (fun _ -> ServerAgent.make "uninitialised")
 
         let mutable data = ""
+
         let getInfo =
             async {
                 // Simulate a slow network call
@@ -95,6 +106,7 @@ module TestPulsingServer =
                 let result = lock data (fun () -> sprintf "%s" data)
                 return result
             }
+
         let _infoProvider =
             ExternalInfoProvider.make Async.Sleep getInfo 10<ms> responders
             |> Async.RunSynchronously
@@ -107,13 +119,17 @@ module TestPulsingServer =
         // n requests come in - note that we don't start them off yet,
         // because we want to time them separately
         let requests =
-            Array.init n (fun i ->
+            Array.init
+                n
+                (fun i ->
                     async {
                         let! answer = ServerAgent.giveNextResponse responders.[i % queues]
-                    if answer <> "" then failwith "unexpected response!"
+
+                        if answer <> "" then
+                            failwith "unexpected response!"
+
                         return ()
-                }
+                    })
-            )
             |> Async.Parallel
             |> Async.Ignore
 
@@ -122,8 +138,7 @@ module TestPulsingServer =
 
         time.Restart ()
 
-        requests
+        requests |> Async.RunSynchronously
-        |> Async.RunSynchronously
 
         time.Stop ()
         printfn "Time to execute: %i ms" time.ElapsedMilliseconds
@@ -131,8 +146,11 @@ module TestPulsingServer =
         // Now prepare n more requests, but halfway through, we'll be changing the data.
         // Again, don't kick them off right now; wait for the timer.
         time.Restart ()
+
         let requests =
-            Array.init n (fun i ->
+            Array.init
+                n
+                (fun i ->
                     if i = n / 2 then
                         async {
                             lock data (fun () -> data <- "new data")
@@ -143,30 +161,32 @@ module TestPulsingServer =
                             do! Async.Sleep (TimeSpan.FromMilliseconds (float i))
                             let! response = ServerAgent.giveNextResponse (responders.[i % queues])
                             return Some response
-                    }
+                        })
-            )
             |> Async.Parallel
+
         time.Stop ()
 
         printfn "Time to construct requests: %i ms" time.ElapsedMilliseconds
 
         time.Restart ()
 
-        let results =
+        let results = requests |> Async.RunSynchronously
-            requests
-            |> Async.RunSynchronously
 
         time.Stop ()
         printfn "Time to execute: %i ms" time.ElapsedMilliseconds
 
         let grouped =
-            results
+            results |> Array.countBy id |> Map.ofArray
-            |> Array.countBy id
-            |> Map.ofArray
 
         grouped.[None] |> shouldEqual 1
-        let pre = Map.tryFind (Some "") grouped |> Option.defaultValue 0
+
-        let post = Map.tryFind (Some "new data") grouped |> Option.defaultValue 0
+        let pre =
+            Map.tryFind (Some "") grouped
+            |> Option.defaultValue 0
+
+        let post =
+            Map.tryFind (Some "new data") grouped
+            |> Option.defaultValue 0
 
         pre + post |> shouldEqual (n - 1)
         printfn "Got old data: %i. Got new data: %i." pre post

test.fsx

@@ -1,17 +1,15 @@
 open System.Net
 open System.Diagnostics
 
-use timer = new Stopwatch()
+let timer = new Stopwatch()
 timer.Restart()
 
-[
+[ for i in 1 .. 1000 do
-    for i in 1..1000 do
     yield
         async {
             let w = new WebClient()
             return w.DownloadString("http://localhost:5000/")
-            }
+        } ]
-]
 |> Async.Parallel
 |> Async.RunSynchronously