How to ignore ETag checking

Question

My application reads blob content from Azure blob storage. The Blob content file is being changed by another program at the same time while it is being read. I get error in the Read() line. Which I believe is because of mismatch eTag values as file is both read and written at the same time.

How can I make my application ignore checking for ETag value (Which is disabling concurrency check). Tried as below. But same error.

    BlobRequestConditions blobRequestConditions = new BlobRequestConditions
    {
           IfMatch = new ETag("*")
           //IfMatch = ETag.All
    };

   using (var stream = await blob.OpenReadAsync(offset, sgmtSize, blobRequestConditions)) 
   {
      
        stream.Read(); // ERROR in this line
   }

Read() error below:

Azure.RequestFailedException: The condition specified using HTTP conditional header(s) is not met.
RequestId:0000000
Time:2022-05-16T10:37:49.1672314Z
Status: 412 (The condition specified using HTTP conditional header(s) is not met.)
ErrorCode: ConditionNotMet

AFAIK if the `IfMatch` is not set, no ETag check is done, so setting it to some magic value like `*` should not be needed. — Oliver, Jan 18 '23 at 06:53
I am actually not setting any "conditional headers" in the request (As you could see the error details, I believe something is happening under the covers that I'm not aware of). Please correct me if my understanding is wrong. — Sarahrb, Jan 18 '23 at 06:56
I retried adding more accurate code as above (for Azure.Storage.Blobs). Still get the same error at times. Would appreciate if you have any inputs. — Sarahrb, Jan 19 '23 at 09:38

score 1 · Answer 1 · answered Jan 23 '23 at 15:19

BlobProperties properties1 = await blob.GetPropertiesAsync();
string originalETag = properties.ETag;
bool retry = true;
while (retry)
{    

      try{ 
    
            BlobRequestConditions blobRequestConditions = new BlobRequestConditions
            {
                  IfMatch = new ETag(originalETag)
            };
        
            using (var stream = await blob.OpenReadAsync(offset, segmentSize, blobRequestConditions)) 
            retry = false;

        }
        catch(RequestFailedException ex){
               if (ex.ErrorCode == "ConditionNotMet")
                {
                     retry = true;
                }
                       
                else
                {
                    System.Diagnostics.Debug.WriteLine("Failed to Read");
                    throw;
                 }   
         }
 }

score 0 · Answer 2 · answered Jan 20 '23 at 18:55

0

If you dont pass the blobRequestConditions to the method, it will disable the concurrency check

using (var stream = await blob.OpenReadAsync(offset, segmentSize))

answered Jan 20 '23 at 18:55

Jonxag

766
7
20

Hi, my initial code was without the definition of blobRequestConditions or passing it as a parameter but I got this error. Since I was getting this error, I am rite now trying blobRequestConditions to see if I can resolve this. – Sarahrb Jan 21 '23 at 10:32
If I am not wrong concurrency check is somehow set under the covers. Which is why this error occurs. – Sarahrb Jan 21 '23 at 10:34
Is possible to lock it for reading or is not possible on this scenario? – Jonxag Jan 23 '23 at 12:15
1

I got it working, please see the answer below. Thank you for trying to help. – Sarahrb Jan 23 '23 at 15:20

How to ignore ETag checking

2 Answers2