はじめに

Azure Functio v2のDIサポートが少しづつ進んでいて、
コンストラクタインジェクションが出来るようになっています。

azure-functions-host issue #3736 Dependency Injection support for Functions
しばやん雑記 Azure Functions v2 でインスタンスメソッドも Function として利用可能に

UnitTestが書きやすくなるので、重宝しています。
まだドキュメントが整備されておらず、取っ付き難さがあるので、
よく使いそうなものをサンプルとしてまとめてみました。

おかしいところがあったら突っ込みをぜひお願いします。
ソース全体はこちら GitHub

HttpClient(Factory + Polly)

NuGet

Microsoft.Azure.Functions.Extensions 1.0.0
Microsoft.NET.Sdk.Functions >= 1.0.27
Microsoft.Extensions.Http.Polly 2.2.0

Startup

HttpClientStartup.cs

[assembly: FunctionsStartup(typeof(AzFuncDISample.HttpClientStartup))]
namespace AzFuncDISample
{
    public class HttpClientStartup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            //HttpClient
            builder.Services.AddHttpClient("httpstat", (provider,httpClient) =>
            {
                var configuration = provider.GetRequiredService<IConfiguration>();
                var hostName = configuration.GetValue<string>("Test:HostName");
                httpClient.BaseAddress = new Uri($"https://{hostName}/");
                httpClient.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
            })
            .ConfigurePrimaryHttpMessageHandler(() => GetHttpMessageHandler());

            //HttpClient with Polly
            builder.Services.AddHttpClient("httpstatWithPolly", (provider, httpClient) =>
            {
                var configuration = provider.GetRequiredService<IConfiguration>();
                var hostName = configuration.GetValue<string>("Test:HostName");
                httpClient.BaseAddress = new Uri($"https://{hostName}/");
                httpClient.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
            })
            .SetHandlerLifetime(System.Threading.Timeout.InfiniteTimeSpan)
            .AddPolicyHandler(HttpPolicyExtensions
                .HandleTransientHttpError()
                .OrResult(msg => msg.StatusCode == HttpStatusCode.NotFound || (int)msg.StatusCode == 429)
                .Or<TimeoutRejectedException>()
                .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))
                ))
            .AddPolicyHandler(Policy.TimeoutAsync<HttpResponseMessage>(TimeSpan.FromSeconds(10)))
            .ConfigurePrimaryHttpMessageHandler(() => GetHttpMessageHandler());
        }
    }
}

Function

HttpClientFunction.cs

public class HttpClientFunction
{
    private readonly IHttpClientFactory httpClientFactory;
    private readonly HttpClient httpClient1;
    private readonly HttpClient httpClient2;
    public HttpClientFunction(IHttpClientFactory httpClientFactory)
    {
        this.httpClientFactory = httpClientFactory;
        httpClient1 = this.httpClientFactory.CreateClient("httpstat");
        httpClient2 = this.httpClientFactory.CreateClient("httpstatWithPolly");
    }
    [FunctionName(nameof(HttpClientFunction))]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function)] HttpRequest request,
        ILogger log)
    {
        string responseText1 = await httpClient1.GetStringAsync("/200");
        string responseText2 = null;
        try
        {
            responseText2 = await httpClient2.GetStringAsync("/429");
        }
        catch (Exception ex)
        {
            responseText2 = ex.ToString();
        }
        return new OkObjectResult(new
        {
            responseText1,
            responseText2,
        });
    }
}

IConfiguration

Startup

不要

Function

IConfigurationFunction.cs

public class IConfigurationFunction
{
    private readonly IConfiguration configuration;
    public IConfigurationFunction(IConfiguration configuration)
    {
        this.configuration = configuration;
    }
    [FunctionName(nameof(IConfigurationFunction))]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function)] HttpRequest request,
        ILogger log)
    {
        var configValue = configuration.GetValue<string>("key");
        return new OkObjectResult(new
        {
            configValue,
        });
    }
}

Cosmos DB(DocumentDB Client)

NuGet

Microsoft.Azure.Functions.Extensions 1.0.0
Microsoft.NET.Sdk.Functions >= 1.0.27
Microsoft.Azure.DocumentDB.Core 2.3.0

Startup

DocumentClientStartup.cs

[assembly: FunctionsStartup(typeof(AzFuncDISample.DocumentClientStartup))]
namespace AzFuncDISample
{
    public class DocumentClientStartup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.AddSingleton<IDocumentClient>(provider => {
                var configuration = provider.GetRequiredService<IConfiguration>();

                var accountEndpoint = new Uri(configuration.GetValue<string>("Cosmos:AccountEndpoint"));
                var accountKey = configuration.GetValue<string>("Cosmos:AccountKey");
                var connectionPolicy = new ConnectionPolicy
                {
                    ConnectionMode = ConnectionMode.Direct,
                    ConnectionProtocol = Protocol.Tcp,
                };
                connectionPolicy.RetryOptions.MaxRetryAttemptsOnThrottledRequests = 5;
                connectionPolicy.RetryOptions.MaxRetryWaitTimeInSeconds = 60;
                return new DocumentClient(accountEndpoint, accountKey, connectionPolicy);
            });
        }
    }
}

Function

DocumentClientFunction.cs

public class DocumentClientFunction
{
    private readonly IDocumentClient documentClient;
    public DocumentClientFunction(IDocumentClient documentClient)
    {
        this.documentClient = documentClient;
    }
    [FunctionName(nameof(DocumentClientFunction))]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function)] HttpRequest request,
        ILogger log)
    {
        //適当
        var databaseAccount = await documentClient.GetDatabaseAccountAsync();
        return new OkObjectResult(new
        {
            databaseId = databaseAccount.Id,
        });
    }
}

EFCore(SQLServer)(DBContext)

NuGet

Microsoft.Azure.Functions.Extensions 1.0.0
Microsoft.NET.Sdk.Functions >= 1.0.27
Microsoft.EntityFrameworkCore.SqlServer 2.2.4

Startup

DbContextStartup.cs

[assembly: FunctionsStartup(typeof(AzFuncDISample.DbContextStartup))]
namespace AzFuncDISample
{
    public class DbContextStartup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.AddDbContext<SampleContext>((provider,options) =>
            {
                var configuration = provider.GetRequiredService<IConfiguration>();
                options.UseSqlServer(configuration.GetConnectionString("SampleConnection"));
            });
        }
    }
    //適当
    public class SampleContext : DbContext
    {
        public SampleContext(DbContextOptions<SampleContext> options)
            : base(options)
        { }
        public DbSet<Sample> Samples { get; set; }
    }
    public class Sample
    {
        public int Id { get; set; }
        public string Value { get; set; }
    }
}

Function

DocumentClientFunction.cs

public class DbContextFunction
{
    private readonly SampleContext dbContext;
    public DbContextFunction(SampleContext dbContext)
    {
        this.dbContext = dbContext;
    }
    [FunctionName(nameof(DbContextFunction))]
    public async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function)] HttpRequest request,
        ILogger log)
    {
        //適当
        dbContext.Database.OpenConnection();
        using (var connection = dbContext.Database.GetDbConnection())
        using (var command = connection.CreateCommand())
        {
            command.CommandText = "SELECT COUNT(*) FROM sys.tables";
            var count = (int)await command.ExecuteScalarAsync();
            return new OkObjectResult(count);
        }
    }
}

気になってるところ

~~IWebJobsStartup内でIConfigurationの取り出し方、本当に↓でよいか…?(とりあえず動くけど、はしご外されそうで怖い）~~

var configuration = builder.Services
 .Where(s => s.ServiceType == typeof(IConfiguration)).First()
 .ImplementationInstance as IConfiguration;

2019/07/11 追記

ServiceCollection追加時にFactoryメソッド内で、
IServiceProvider.GetRequierdService()を使用するのが正解だった

builder.Services.AddDbContext<SampleContext>((provider,options) =>
{
  var configuration = provider.GetRequiredService<IConfiguration>();
  options.UseSqlServer(configuration.GetConnectionString("SampleConnection"));
});

終わりに

DI使ったFunction量産してたんですが、3月中旬のランタイムv2.0.12353のバグ↓にやられました。
azure-functions-host issue [#4203 Depdency Injection and Logging start failing on 2.0.12353]　コメント
やっぱり、バージョン固定がいいんですかねぇ…？

2019/5/9 追記

Buildと同時に正式サポートとなったようです

公式ドキュメントはこちら
Use dependency injection in .NET Azure Functions | Microsoft Docs

正式な作法としては、
NuGetPackage Microsoft.Azure.Functions.Extensions 1.0.0の参照を追加して、
IWebJobsStartupではなく、FunctionsStartupを使用するようになったようです。

上記サンプルと GitHub も併せて修正しています。

内部的にはIWebJobsStartupの薄いラッパーでした。
GitHub Azure/azure-functions-dotnet-extensions

Microsoft.Extensions.Configuration.IConfigurationがFunctionHost側で登録されるのは、
ドキュメント化されたので正式なサポートのようです。