c#-使用输入绑定将blob名称匹配到函数变量

根据Azure Blob storage bindings for Azure Functions documentation,在配置Blob触发器时,您可以利用Blob名称上的模式匹配将路径的一部分映射到函数中的变量,例如.

[FunctionName("BlobTriggered")]        
public static void BlobTriggered(
    [BlobTrigger("myContainer/{name}.{extension}")] Stream myBlob,
    string name,
    string extension,
    TraceWriter log)
{
    // Given the blob path "myContainer/myBlob.png":
    // name == "myBlob"
    // extension == "png"
}

我已经对此进行了测试,并且它在我的用例中表现出色,但是由于BlobTrigger触发的延迟较大(通常超过5分钟),因此这不是一个可行的选择.因此,我希望根据Azure Functions scale and hosting documentation的建议,将其设置为事件网格触发器：

When you’re using a blob trigger on a Consumption plan, there can be up to a 10-minute delay in processing new blobs. This delay occurs when a function app has gone idle. After the function app is running, blobs are processed immediately. To avoid this cold-start delay, use an App Service plan with Always On enabled, or use the Event Grid trigger.

有没有办法从输入绑定而不是触发器中获得相同的模式匹配行为？

在我的特定情况下,我为Event Blob设置了EventGrid订阅,该订阅运行一个Orchestrator函数,该Orchestrator函数调用一个Activity函数来读取和解析The Blob：

[FunctionName("NewBlobCreated")]
public static async Task NewBlobCreated(
    [EventGridTrigger]EventGridEvent eventGridEvent,
    [OrchestrationClient]DurableOrchestrationClient starter,
    ILogger log)
{
    // Start our orchestrator function to read the file
    string instanceId = await starter.StartNewAsync(
        "OrchestrateBlobReader",
        eventGridEvent);
}

// Orchestrator function
[FunctionName("OrchestrateBlobReader")]
public static async Task OrchestrateBlobReader(
    [OrchestrationTrigger] DurableOrchestrationContext context,
    ILogger log)
{
    var eventGridEvent = context.GetInput<EventGridEvent>();
    var parsedBlob = await context.CallActivityAsync<string>("ReadBlob", eventGridEvent.Data);        
    ...
}

[FunctionName("ReadBlob")]
public static async Task<string> ReadBlob(
    [ActivityTrigger] JObject eventData,
    [Blob("{data.url}", FileAccess.Read)]CloudBlockBlob blob,
    ILogger log)
{
    using (var blobStream = await blob.OpenReadAsync())
    {
        // Blob is able to be read from blobStream here
        ...
    }
}

理想情况下,我希望我的ReadBlob函数的行为类似于上述第一个示例示例中的BlobTriggered函数,以执行以下操作：

[FunctionName("ReadBlob")]
public static async Task<string> ReadBlob(
    [ActivityTrigger] JObject eventData,
    [Blob("{data.url}", FileAccess.Read)]CloudBlockBlob blob,
    string extension,
    ILogger log)
{
    if (extension.Equals("txt", StringComparison.OrdinalIgnoreCase))
    { ... }
    else if (extension.Equals("png", StringComparison.OrdinalIgnoreCase)
    { ... }
    else
    { ... }
}

问题是我无法像我为BlobTrigger所做的那样看到将扩展参数绑定到Blob输入绑定的任何方法-特别是将路径绑定到EventGridEvent提供的url
以eventData JObject的形式.

在这种情况下是否可以实现相同的模式匹配功能？还是我必须自己解析路径字符串以提取相关信息？

解决方法:

在查看了源代码触发器绑定的源代码之后,我的“快速处理”解决方案是利用底层BindingTemplateSource class,触发器用于映射路径和路径.模式到字典.

更新的ReadBlob函数如下：

// So we can access the BindingTemplateSource class
using Microsoft.Azure.WebJobs.Host.Bindings.Path;

[FunctionName("ReadBlob")]
public static async Task<string> ReadBlob(
    [ActivityTrigger] JObject eventData,
    [Blob("{data.url}", FileAccess.Read)]CloudBlockBlob blob,
    ILogger log)
{
    // Define the pattern to match
    var blobPattern = "myContainer/{name}.{extension}";
    // Create a BindingTemplateSource from the pattern string
    var patternTemplate = BindingTemplateSource.FromString(blobPattern);
    // Use this BindingTemplateSource to create the binding data
    // This returns a IReadOnlyDictionary<string, object> with the parameters mapped
    var parameters = patternTemplate.CreateBindingData($"{blob.Container.Name}/{blob.Name}");
    // Assuming blob path was "myContainer/myBlob.png":
    // Parameters are objects so we need to ToString() them
    var name = parameters["name"].ToString(); // name == "myBlob"
    var extension = parameters["extension"].ToString(); // extension == "png"

    if (extension.Equals("txt", StringComparison.OrdinalIgnoreCase))
    { ... }
    else if (extension.Equals("png", StringComparison.OrdinalIgnoreCase))
    { 
        // This executes now!
    }
    else
    { ... }
}

然后,可以将此功能包装在custom binding中,在其中将参数映射到函数上的输出绑定,就像BlobTrigger为最优雅的解决方案所做的那样,但是将其侵入这样的函数中可以满足我短期的需求

标签：azure-storage-blobs,azure-functions,c
来源： https://codeday.me/bug/20191108/2008368.html