f# - 在 F# 中的模块级别创建私有静态字段

问题描述

我正在尝试创建一个可在 Azure Functions 中沿请求重用的已配置对象。下面的示例是在 C# 中。这个想法是为了避免DocumentClient为每个请求创建昂贵的自定义实例。该client字段是静态的，在此示例中重用，取自文档：

using System;
using System.Configuration;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.Azure.Documents;
using Microsoft.Azure.Documents.Client;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Host;

private static DocumentClient client = GetCustomClient();
private static DocumentClient GetCustomClient()
{
    DocumentClient customClient = new DocumentClient(
        new Uri(ConfigurationManager.AppSettings["CosmosDBAccountEndpoint"]), 
        ConfigurationManager.AppSettings["CosmosDBAccountKey"],
        new ConnectionPolicy
        {
            ConnectionMode = ConnectionMode.Direct,
            ConnectionProtocol = Protocol.Tcp,
            // Customize retry options for Throttled requests
            RetryOptions = new RetryOptions()
            {
                MaxRetryAttemptsOnThrottledRequests = 10,
                MaxRetryWaitTimeInSeconds = 30
            }
        });

    // Customize PreferredLocations
    customClient.ConnectionPolicy.PreferredLocations.Add(LocationNames.CentralUS);
    customClient.ConnectionPolicy.PreferredLocations.Add(LocationNames.NorthEurope);

    return customClient;
}

[FunctionName("CosmosDbSample")]
public static async Task<HttpResponseMessage> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "foo/{id}")] HttpRequestMessage req,
    string id,
    TraceWriter log)
{
    Uri documentUri = UriFactory.CreateDocumentUri("ToDoList", "Items", id);
    Document doc = await client.ReadDocumentAsync(documentUri);

    if (doc == null)
    {
        return req.CreateResponse(HttpStatusCode.NotFound);
    }

    return req.CreateResponse(HttpStatusCode.OK, doc);
}

为了尝试用一个更简单的例子来模拟，我尝试了下面的代码。它可以正常工作：

namespace TransactionsAggregate

open Microsoft.AspNetCore.Http
open Microsoft.Azure.WebJobs
open Microsoft.Azure.WebJobs.Host
open Microsoft.Azure.WebJobs.Extensions.Http
open System.Net
open System.Net.Http
open System.Web.Http
open Newtonsoft.Json
open System.Text


module Ping =    


    type Name = {
        First: string
        Last: string
    }

    type Greeting = {
        Greeting: string
    }


    let jsonFormatter = System.Net.Http.Formatting.JsonMediaTypeFormatter()
    jsonFormatter.SerializerSettings.ContractResolver <- new Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver()



    [<FunctionName("Ping1")>]
    let run([<HttpTrigger>] req: HttpRequest, log: TraceWriter) =
        async {

        log.Info("Chamando Ping 1")
        let! jsonContent = req.ReadAsStringAsync() |> Async.AwaitTask

        try
            let name = JsonConvert.DeserializeObject<Name>(jsonContent, jsonFormatter.SerializerSettings)

            let response = new HttpResponseMessage(HttpStatusCode.OK)
            let body = JsonConvert.SerializeObject( { Greeting = sprintf "Hello %s %s!" name.First name.Last })
            let content = new StringContent(body, Encoding.UTF8, "application/json")
            response.Content <- content
            return response

        with _ ->
            return new HttpResponseMessage(HttpStatusCode.BadRequest)
        } |> Async.StartAsTask

在这个 F# 示例中，我们有一个在 V2 版本上运行并在 .NET Core 上编写的 Azure 函数。这是一个预编译函数（不是脚本）。这是一个类库项目。这个例子只是回显了传递的参数。jsonFormatter是在模块级别定义和配置的，并且没有标记为静态的。有没有办法创建一个类似的静态字段，这样我就可以缓存这个 jsonFormatter 或者在将来，一个更昂贵的对象？此外，是否可以保证应用程序上只有一个该值的实例？

文档：https ://docs.microsoft.com/en-us/sandbox/functions-recipes/cosmos-db

提前致谢

标签： f#azure-functions

f# - 在 F# 中的模块级别创建私有静态字段

问题描述

解决方案

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