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Azure存储blob的乐观并发总是抛出HTTP 412

azure .net

0

Kristoffer Jälén · 技术社区 · 7 年前

如果匹配AccessCondition

如果另一个进程更新了blob,则blob服务应返回http412(Precondition Failed)状态消息。但是,服务是

对于本例,我使用Storage Explorer手动查找了ETag值。

var storage = CloudStorageAccount.Parse(connectionString);

var blobClient = storage.CreateCloudBlobClient();

var container = blobClient.GetContainerReference("foo");

var blob = container.GetBlockBlobReference("foo/1");

await blob.UploadTextAsync(
          "test", 
           Encoding.UTF8,
           AccessCondition.GenerateIfMatchCondition("\"0x1A52537587A1234\""),
           new BlobRequestOptions(),
           null);

2 回复 | 直到 7 年前

1

Kristoffer Jälén 7 年前

问题是我不小心用错了 blobName :

var blob = container.GetBlockBlobReference("foo/1");

应该是:

var blob = container.GetBlockBlobReference("1");

foo/1

2

0

Joey Cai 7 年前

当你上传带有特定 ETAG 价值,这将是第一次工作。但是,当您第二次上载blob时 ETAG公司 它将抛出412错误。因为一旦你操作了blob ETAG公司 将更新。

blob和容器的乐观并发

ETag 以及一个条件头,以确保只有在满足某个条件时才会发生更新。在本例中,该条件是 If-Match 头,它需要存储服务来确保 ETag公司 更新请求中指定的与存储服务中存储的相同。

// Retrieve Etag from the response of an earlier UploadText blob operation.
string orignalETag = blockBlob.Properties.ETag;
// This code simulates an update by a third party.
string helloText = "Blob updated by a third party.";
// No etag, provided so orignal blob is overwritten (thus generating a new etag)
blockBlob.UploadText(helloText);
Console.WriteLine("Blob updated. Updated ETag = {0}", blockBlob.Properties.ETag);
// Now try to update the blob using the orignal ETag provided when the blob was created
try
{
     Console.WriteLine("Trying to update blob using orignal etag to generate if-match access condition");
     blockBlob.UploadText(helloText,accessCondition:
     AccessCondition.GenerateIfMatchCondition(orignalETag));
}
catch (StorageException ex)
{
     if (ex.RequestInformation.HttpStatusCode == (int)HttpStatusCode.PreconditionFailed)
     {
          Console.WriteLine("Precondition failure as expected. Blob's orignal etag no longer matches");
     }
}

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