在异步方法中绑定到输出 blob 时，将 Blob 绑定到 IAsyncCollector 时出错

Question

我正在尝试按照此 post 以异步方法绑定到 blob 输出：

我有多个输出绑定，所以只返回不是一个选项

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, IAsyncCollector<string> collection, TraceWriter log)
{
    if (req.Method == HttpMethod.Post) 
    {
        string jsonContent = await req.Content.ReadAsStringAsync();

        // Save to blob 
        await collection.AddAsync(jsonContent);

        return req.CreateResponse(HttpStatusCode.OK);
    }
    else 
    {
        return req.CreateResponse(HttpStatusCode.BadRequest);

    }
}

我对 blob 的绑定是：

{
  "bindings": [
    {
      "authLevel": "function",
      "name": "req",
      "type": "httpTrigger",
      "direction": "in"
    },
    {
      "name": "$return",
      "type": "http",
      "direction": "out"
    },
    {
      "type": "blob",
      "name": "collection",
      "path": "testdata/{rand-guid}.txt",
      "connection": "test_STORAGE",
      "direction": "out"
    }
  ],
  "disabled": false
}

但每当我这样做时，我都会得到以下信息：

Error: Function ($WebHook) Error: Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.WebHook'. Microsoft.Azure.WebJobs.Host: Can't bind Blob to type 'Microsoft.Azure.WebJobs.IAsyncCollector`1[System.String]'

Answer 1

Blob 输出绑定不支持收集器，请参阅此 issue。

对于可变数量的输出 blob（在您的情况下为 0 或 1，但可以是任意值），您将不得不使用命令式绑定。从 function.json 中删除 collection 绑定，然后执行此操作：

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, Binder binder)
{
    if (req.Method == HttpMethod.Post) 
    {
        string jsonContent = await req.Content.ReadAsStringAsync();

        var attributes = new Attribute[]
        {    
            new BlobAttribute("testdata/{rand-guid}.txt"),
            new StorageAccountAttribute("test_STORAGE")
        };

        using (var writer = await binder.BindAsync<TextWriter>(attributes))
        {
            writer.Write(jsonContent);
        }

        return req.CreateResponse(HttpStatusCode.OK);
    }
    else 
    {
        return req.CreateResponse(HttpStatusCode.BadRequest);    
    }
}

Answer 2

您可以使用 Blob-Binding。

我更喜欢这种方式，因为我可以指定 ContentType。

 [FunctionName(nameof(Store))]
    public static async Task<IActionResult> Store(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
        [Blob(
            "firstcontainer",
            FileAccess.Read,
            Connection = "blobConnection")] CloudBlobContainer blobContainer,
        ILogger log)
    {
        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();

        string filename = "nextlevel/body.json";

        CloudBlockBlob blob = blobContainer.GetBlockBlobReference($"{filename}");
        blob.Properties.ContentType = "application/json";
        await blob.UploadTextAsync(requestBody);

        return (ActionResult)new OkResult();
    }

在异步方法中绑定到输出 blob 时，将 Blob 绑定到 IAsyncCollector 时出错

Error binding Blob to IAsyncCollector when binding to output blob in Async method

c#

asynchronous

azure

azure-blob-storage

azure-functions