Writing to Azure Block Blobs - azure

Question

I am using PutBlock and PutBlockList to upload data to a block blob, the code i am using for this is below:-
CloudBlobContainer container = blobStorage.GetContainerReference("devicebackups");
var permissions = container.GetPermissions();
permissions.PublicAccess = BlobContainerPublicAccessType.Container;
container.SetPermissions(permissions);
CloudBlockBlob blob = container.GetBlockBlobReference(serialNo.ToLower() + " " + dicMonths[DateTime.Now.Month]);
try
{
var serializer = new XmlSerializer(typeof(List<EnergyData>));
var stringBuilder = new StringBuilder();
using (XmlWriter writer = XmlWriter.Create(stringBuilder))
{
try
{
serializer.Serialize(writer, deviceData);
byte[] byteArray = Encoding.UTF8.GetBytes(stringBuilder.ToString());
List<string> blockIds = new List<string>();
try
{
blockIds.AddRange(blob.DownloadBlockList(BlockListingFilter.Committed).Select(b => b.Name));
}
catch (StorageClientException e)
{
if (e.ErrorCode != StorageErrorCode.BlobNotFound)
{
throw;
}
blob.Container.CreateIfNotExist();
}
var newId = Convert.ToBase64String(Encoding.UTF8.GetBytes(blockIds.Count().ToString()));
blob.PutBlock(newId, new MemoryStream(byteArray), null);
blockIds.Add(newId);
blob.PutBlockList(blockIds);
}
catch (Exception ex)
{
UT.ExceptionReporting(ex, "Error in Updating Backup Blob - writing byte array to blob");
}
}
}
catch (Exception ex)
{
UT.ExceptionReporting(ex, "Error in Updating Backup Blob - creating XmlWriter");
}
}
catch (Exception ex)
{
UT.ExceptionReporting(ex, "Error in Updating Backup Blob - getting container and blob references, serial no -" + serialNo);
}
This works for 10 blocks, then on the 11th block it crashes with the following error:-
StorageClientException - The specified block list is invalid.
InnerException = {"The remote server returned an error: (400) Bad Request."}
I have searched the internet for reports of the same error, but had no luck.
Any help would be much appreciated.

Answer 1

For a given blob, the length of the value specified for the blockid
parameter must be the same size for each block.
http://msdn.microsoft.com/en-us/library/windowsazure/dd135726.aspx
The first 10 blocks are numbered 0 through 9. The 11th block is number 10, which is longer by one character. So you should change your numbering scheme to always use the same length. One solution would be to convert the count to a zero-padded string that's long enough to hold the number of blocks you expect to have.
But if you don't need the benefits of using blocks, you're probably better off just writing the whole blob in one go instead of using blocks.

Answer 2

Set your BlockID has below code
var blockIdBase64 = Convert.ToBase64String(Encoding.UTF8.GetBytes(blockId.ToString(CultureInfo.InvariantCulture).PadLeft(32, '0')));

Answer 3

My problem was that after 10 put block I received the bad request (Error 400).
Replaced Encoding.UTF8.GetBytes with
System.BitConverter.GetBytes string
blockIdBase64=Convert.ToBase64String(System.BitConverter.GetBytes(x++));
The blockIDs must be same size. BitConverter.GetBytes does the
work.
I still received the bad request (Error 400). I solved it by
deleting the temp blob with 'Azure storage explorer'. It is like
resetting the temporary block from my previous bad tries.