DurableFunctions.FSharp

KO | EN

gitlite — search

#hacktoberfest #ai #typescript #llm #rust #macos #nodejs #cli #kubernetes #security #openai #mcp #ios #open-source

DurableFunctions.FSharp

(★ 62)

F#-friendly API layer for Azure Durable Functions

DurableFunctions.FSharp 최신버젼 다운로드

최종 버전 다운로드 (.zip)

// repository documentation

Was this content helpful?

★ 0 (0 ratings)

DurableFunctions.FSharp Library
-------------------------------

F#-friendly API layer around 
[Azure Functions Durable Extensions](https://github.com/Azure/azure-functions-durable-extension).

*Note: this is an early draft with the primary goal to gather feedback,
opinions, real-world scenarios and refine the API. Breaking changes
may be introduced at any time.*

Getting Started
---------------

Here is how you get started :

#### 1. Create a new .NET Core console application

With .NET Core 2.1 installed, run the following command to create a new console application:

```
dotnet new console -lang F#
```

#### 2. Modify `fsproj`

Edit the top section in `fsproj` to be:

``` xml
<PropertyGroup>
  <TargetFramework>netcoreapp2.1</TargetFramework>
  <AzureFunctionsVersion>v2</AzureFunctionsVersion>
</PropertyGroup>
```

See [the example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/samples.fsproj#L3-L6).

#### 3. Install NuGet package

Install the `Microsoft.NET.Sdk.Functions` and `DurableFunctions.FSharp` NuGet packages:

```
dotnet add package Microsoft.NET.Sdk.Functions
dotnet add package DurableFunctions.FSharp
```

#### 4. Define an activity and an orchestrator

The following Hello World application can be used as a starting point:

``` fsharp
namespace MyDurableApp

open Microsoft.Azure.WebJobs
open DurableFunctions.FSharp

module TypedSequence =

let sayHello = 
    Activity.define "SayHello" (sprintf "Hello %s!")

let workflow = orchestrator {
    let! hello1 = Activity.call sayHello "Tokyo"
    let! hello2 = Activity.call sayHello "Seattle"
    let! hello3 = Activity.call sayHello "London"

// returns ["Hello Tokyo!", "Hello Seattle!", "Hello London!"]
    return [hello1; hello2; hello3]
  }

[<FunctionName("SayHello")>]
  let SayHello([<ActivityTrigger>] name) = Activity.run sayHello

[<FunctionName("TypedSequence")>]
  let Run ([<OrchestrationTrigger>] context: DurableOrchestrationContext) =
    Orchestrator.run (workflow, context)
```

#### 5. Run

[Install Azure Functions Core Tools](https://docs.microsoft.com/en-us/azure/azure-functions/functions-run-local)
to run the app locally and deploy to the cloud, or use the tooling in Visual Studio or Visual Studio Code.

If you have any issue, you can also clone/fork
[the samples](https://github.com/mikhailshilkov/DurableFunctions.FSharp/tree/master/samples).

Basic Orchestrator
------------------

Durable Orchestrators are not allowed to use `async` computation expression due to the
requirement of being single-threaded. Orchestrators can be defined with `task` computation 
expression, as shown in the standard
[samples](https://github.com/Azure/azure-functions-durable-extension/blob/master/samples/fsharp/HelloSequence.fs#L12-#L19).

However, to enable a more F#-idiomatic style of orchestrator definitions, this library
defines a new computation expression called `orchestrator`.

Given a simple activity function:

``` fsharp
[<FunctionName("SayHello")>]
let SayHello([<ActivityTrigger>] name) = 
    sprintf "Hello %s!" name
```

An orchestrator can be defined as follows:

``` fsharp
let workflow = orchestrator {
    let! hello1 = Activity.callByName<string> "SayHello" "Tokyo"
    let! hello2 = Activity.callByName<string> "SayHello" "Seattle"
    let! hello3 = Activity.callByName<string> "SayHello" "London"

// returns ["Hello Tokyo!", "Hello Seattle!", "Hello London!"]
    return [hello1; hello2; hello3]
}
```

The result of the computation is a function of type `DurableOrchestrationContext -> Task<'a>`
which can be invoked from the orchestrator Azure Function:

``` fsharp
[<FunctionName("HelloSequence")>]
let Run ([<OrchestrationTrigger>] context: DurableOrchestrationContext) = 
    Orchestrator.run (workflow, context)
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/Hello.fs).

Typed Activity
--------------

In the example above, the orchestrator calls activities by name. It also specifies the
return type explicitly.

To gain more type safety, an explicit typed `Activity<'a, 'b>` may be defined:

``` fsharp
let sayHello = 
    Activity.define "SayTyped" (sprintf "Hello typed %s!")
```

`Activity.define` accepts the function name as the first parameter and the function `'a -> 'b`
as the second parameter. Azure Function still has to be defined separately:

``` fsharp
[<FunctionName("SayTyped")>]
let SayHello([<ActivityTrigger>] name) = Activity.run sayHello name
```

The orchestrator can now infer types from the activity type:

``` fsharp
let workflow = orchestrator {
    let! hello1 = Activity.call sayHello "Tokyo"
    let! hello2 = Activity.call sayHello "Seattle"
    let! hello3 = Activity.call sayHello "London"

// returns ["Hello typed Tokyo!", "Hello typed Seattle!", "Hello typed London!"]
    return [hello1; hello2; hello3]
}
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/Typed.fs).

`Async` in activities
---------------------

While `Async<'a>` return type is not supported out of the box by Azure Functions, it can
be used internally. There is a helper `defineAsync` function to make such definition easier:

``` fsharp
let hardWork = 
    fun item -> async {
      do! Async.Sleep 1000
      return sprintf "Worked hard on %s!" item
    }
    |> Activity.defineAsync "HardWork"
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/FanOutFanIn.fs).

Orchestrator with an input parameter
------------------------------------

Orchestrators can accept an input parameter (1 at most). This can be defined as an argument of the workflow
definition function:

``` fsharp
let workflow input = orchestrator {
  // ...
}
```

An overload of `Orchestrator.run` will get the input from the context and pass it to the workflow.

Fan-out/fan-in
--------------

`Activity.all` helper function can be used to run multiple activities in parallel and
combine the results:

``` fsharp
let workflow = orchestrator {
    let! items =
      ["Tokyo"; "Seattle"; "London"]
      |> List.map (Activity.call hardWork)
      |> Activity.all

return String.concat ", " items
}
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/FanOutFanIn.fs).

Delays
------

You can pause the orchestrator by calling `Orchestrator.delay` function:

``` fsharp
let sendAndPause email = orchestrator {
    do! Activity.call sendNewsletter email
    do! Orchestrator.delay (TimeSpan.FromHours 1.0)
}
```

Note that the durable timer is used to implement this delay, so the orchestrator function will actually stop the current
execution and will resume after the delay expires. See [Timers in Durable Functions](https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-timers).

Retry
-----

There is a built-in mechanism to retry failed activity calls. Invoke `Activity.callWithRetries` function with retry parameters:

``` fsharp
let workflow = orchestrator {
    let policy = ExponentialBackOff { MaxNumberOfAttempts = 5
                                      FirstRetryInterval = TimeSpan.FromSeconds 1.
                                      BackoffCoefficient = 2. }
    return! Activity.callWithRetries policy failUntil3 "Jam"
}
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/Retry.fs).

Waiting For External Events
---------------------------

Orchestrator functions have the ability to wait and listen for external events. This feature of Durable Functions is often useful for handling human interaction or other external triggers.

`Orchestrator.waitForEvent` accepts the time-out duration and returns a `Result<'a, string>`: an `Ok` result if an external event occured, and `Error` otherwise:

``` fsharp
let workflow = orchestrator {
    let maxWaitDuration = TimeSpan.FromHours 1.
    let! result = Orchestrator.waitForEvent maxWaitDuration "Ack"
    return 
        match result with
        | Ok Ack -> true
        | _ -> false
}
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/WaitForEvent.fs).

"Eternal" Orchestrators
-----------------------

Normal orchestrators persist full history of past events, which means there's a practical limit of how many event they can store without slowing down too much.

[Eternal orchestrators](https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-eternal-orchestrations) solve this problem: the orchestrator can restart itself from a clean sheet. Each iteration will start the history from scratch. However, a piece of data can be forwarded from the previous iteration to the next one.

`Orchestrator.runEternal` accepts a workflow which should return a value of a special type `EternalOrchestrationCommand`, which is a discriminated union. `ContinueAsNew of 'a` case can be used to restart the workflow and pass the value, while `Stop` case will end the orchestration (they don't have to be really eternal).

``` fsharp
let workflow = orchestrator {
    let! s = Activity.call printTime DateTime.Now
    do! Orchestrator.delay (TimeSpan.FromSeconds 5.0)
    return ContinueAsNew ()
}

[<FunctionName("Eternal")>]
let Run ([<OrchestrationTrigger>] context: DurableOrchestrationContext) =
    Orchestrator.runEternal (workflow, context)
```

See [the full example](https://github.com/mikhailshilkov/DurableFunctions.FSharp/blob/master/samples/Eternal.fs).

Contributions
-------------

Everybody is welcome to contribute! Please try the library and create an issue with
your ideas, problems, suggestions and target scenarios.

DurableFunctions.FSharp

DurableFunctions.FSharp 최신버젼 다운로드

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

DurableFunctions.FSharp

DurableFunctions.FSharp 최신버젼 다운로드

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

Download README