NodeJS Azure Function to copy blob across storage account

Question

I have a private storage account with a container. When i upload a blob to the container, I trigger a 'BlobCreated' event with Event Grid, which is then picked up by a function.

The aim of the function is to copy the source blob to another 'backup' storage account.

I am using the new @azure/storage-blob & @azure/identity NodeJS packages.

const {BlobServiceClient} = require('@azure/storage-blob');
const {ManagedIdentityCredential} = require('@azure/identity');

I create my source and destination blob & container clients, then create the destination container. This all works well:

 const sourceBlobServiceClient = new BlobServiceClient(
    `https://${sourceAccountName}.blob.core.windows.net`,
    new ManagedIdentityCredential()
  );

  const destBlobServiceClient = new BlobServiceClient(
    `https://${destinationAccountName}.blob.core.windows.net`,
    new ManagedIdentityCredential()
  );

const sourceContainer = sourceBlobServiceClient.getContainerClient(containerName);
const destContainer = destBlobServiceClient.getContainerClient(containerName);
await destContainer.createIfNotExists();

Then I get source & destination blob clients and initiate the copy:

    const sourceBlob = sourceContainer.getBlobClient(blobName);
    const destBlob = destContainer.getBlobClient(sourceBlob.name);
    const response = await destBlob.beginCopyFromURL(sourceBlob.url);

The sourceBlob.url property is correct, and the blob exists in the source directory, but the beginCopyFromURL statement fails with:

Result: FailureException: RestError: The specified resource does not exist.

I have enabled ManagedIdentity on my function app, and given it Owner & Storage Blob Data Owner on both source & destination storage accounts. It seems like beginCopyFromURL isn't authentication with the identity, instead trying to access the source blob as public.

Am i missing something, or maybe there's a better way to copy across storage accounts using Node?

Thanks

Tester_123 Tester_123 · Accepted Answer · 2021-01-26T10:42:18

I raised this issue on Github and turns out this is by design.

The source for a Copy Blob From URL operation can be any committed block blob in any Azure storage account which is either public or authorized with a shared access signature. The size of the source blob can be a maximum length of up to 256 MiB. https://docs.microsoft.com/en-us/rest/api/storageservices/copy-blob-from-url

You should append a SAS to the source URL if the source blob is under another account.

NodeJS Azure Function to copy blob across storage account

1 Answers