Copy data to or from Azure Blob storage by using Azure Data Factory

• 08/17/2018
• 13 minutes to read
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This article outlines how to use Copy Activity in Azure Data Factory to copy data to and from Azure Blob storage. It builds on the Copy Activity overview article that presents a general overview of Copy Activity.

Supported capabilities

You can copy data from any supported source data store to Blob storage. You also can copy data from Blob storage to any supported sink data store. For a list of data stores that are supported as sources or sinks by the copy activity, see the Supported data stores table.

Specifically, this Blob storage connector supports:

• Copying blobs to and from general-purpose Azure storage accounts and hot/cool blob storage.
• Copying blobs by using account key, service shared access signature, service principal or managed identities for Azure resources authentications.
• Copying blobs from block, append, or page blobs and copying data to only block blobs. Azure Premium Storage isn't supported as a sink because it's backed by page blobs.
• Copying blobs as is or parsing or generating blobs with supported file formats and compression codecs.

Get started

You can use one of the following tools or SDKs to use Copy Activity with a pipeline. Select a link for step-by-step instructions:

• Copy Data tool
• Azure portal
• .NET SDK
• Python SDK
• Azure PowerShell
• REST API
• Azure Resource Manager template

The following sections provide details about properties that are used to define Data Factory entities specific to Blob storage.

Linked service properties

Azure Blob connector support the following authentication types, refer to the corresponding section on details:

• Account key authentication
• Shared access signature authentication
• Service principal authentication
• Managed identities for Azure resources authentication

Account key authentication

To use storage account key authentication, the following properties are supported:

Example:

{
    "name": "AzureBlobStorageLinkedService",
    "properties": {
        "type": "AzureBlobStorage",
        "typeProperties": {
            "connectionString": {
                "type": "SecureString",
                "value": "DefaultEndpointsProtocol=https;AccountName=<accountname>;AccountKey=<accountkey>"
            }
        },
        "connectVia": {
            "referenceName": "<name of Integration Runtime>",
            "type": "IntegrationRuntimeReference"
        }
    }
}

Shared access signature authentication

A shared access signature provides delegated access to resources in your storage account. You can use a shared access signature to grant a client limited permissions to objects in your storage account for a specified time. You don't have to share your account access keys. The shared access signature is a URI that encompasses in its query parameters all the information necessary for authenticated access to a storage resource. To access storage resources with the shared access signature, the client only needs to pass in the shared access signature to the appropriate constructor or method. For more information about shared access signatures, see Shared access signatures: Understand the shared access signature model.

To use shared access signature authentication, the following properties are supported:

Example:

{
    "name": "AzureBlobStorageLinkedService",
    "properties": {
        "type": "AzureBlobStorage",
        "typeProperties": {
            "sasUri": {
                "type": "SecureString",
                "value": "<SAS URI of the Azure Storage resource>"
            }
        },
        "connectVia": {
            "referenceName": "<name of Integration Runtime>",
            "type": "IntegrationRuntimeReference"
        }
    }
}

When you create a shared access signature URI, consider the following points:

• Set appropriate read/write permissions on objects based on how the linked service (read, write, read/write) is used in your data factory.
• Set Expiry time appropriately. Make sure that the access to Storage objects doesn't expire within the active period of the pipeline.
• The URI should be created at the right container/blob or table level based on the need. A shared access signature URI to a blob allows Data Factory to access that particular blob. A shared access signature URI to an Blob storage container allows Data Factory to iterate through blobs in that container. To provide access to more or fewer objects later, or to update the shared access signature URI, remember to update the linked service with the new URI.

Service principal authentication

For Azure Storage service principal authentication in general, refer to Authenticate access to Azure Storage using Azure Active Directory.

To use service principal authentication, follow these steps:

1. Register an application entity in Azure Active Directory (Azure AD) by following Register your application with an Azure AD tenant. Make note of the following values, which you use to define the linked service:

   • Application ID
   • Application key
   • Tenant ID

2. Grant the service principal proper permission in Azure Blob storage. Refer to Manage access rights to Azure Storage data with RBAC with more details on the roles.

   • As source, in Access control (IAM), grant at least Storage Blob Data Reader role.
   • As sink, in Access control (IAM), grant at least Storage Blob Data Contributor role.

These properties are supported for an Azure Blob storage linked service:

Example:

{
    "name": "AzureBlobStorageLinkedService",
    "properties": {
        "type": "AzureBlobStorage",
        "typeProperties": {            
            "serviceEndpoint": "https://<accountName>.blob.core.windows.net/",
            "servicePrincipalId": "<service principal id>",
            "servicePrincipalKey": {
                "type": "SecureString",
                "value": "<service principal key>"
            },
            "tenant": "<tenant info, e.g. microsoft.onmicrosoft.com>" 
        },
        "connectVia": {
            "referenceName": "<name of Integration Runtime>",
            "type": "IntegrationRuntimeReference"
        }
    }
}

Managed identities for Azure resources authentication

A data factory can be associated with a managed identity for Azure resources, which represents this specific data factory. You can directly use this service identity for Blob storage authentication similar to using your own service principal. It allows this designated factory to access and copy data from/to your Blob storage.

For Azure Storage MSI authentication in general, refer to Authenticate access to Azure Storage using Azure Active Directory.

To use managed identities for Azure resources authentication, follow these steps:

1. Retrieve data factory service identity by copying the value of "SERVICE IDENTITY APPLICATION ID" generated along with your factory.

2. Grant the service principal proper permission in Azure Blob storage. Refer to Manage access rights to Azure Storage data with RBAC with more details on the roles.

   • As source, in Access control (IAM), grant at least Storage Blob Data Reader role.
   • As sink, in Access control (IAM), grant at least Storage Blob Data Contributor role.

These properties are supported for an Azure Blob storage linked service:

Example:

{
    "name": "AzureBlobStorageLinkedService",
    "properties": {
        "type": "AzureBlobStorage",
        "typeProperties": {            
            "serviceEndpoint": "https://<accountName>.blob.core.windows.net/"
        },
        "connectVia": {
            "referenceName": "<name of Integration Runtime>",
            "type": "IntegrationRuntimeReference"
        }
    }
}

Dataset properties

For a full list of sections and properties available for defining datasets, see the Datasets article. This section provides a list of properties supported by the Blob storage dataset.

To copy data to and from Blob storage, set the type property of the dataset to AzureBlob. The following properties are supported.

Example:

{
    "name": "AzureBlobDataset",
    "properties": {
        "type": "AzureBlob",
        "linkedServiceName": {
            "referenceName": "<Azure Blob storage linked service name>",
            "type": "LinkedServiceReference"
        },
        "typeProperties": {
            "folderPath": "mycontainer/myfolder",
            "fileName": "myfile.csv.gz",
            "format": {
                "type": "TextFormat",
                "columnDelimiter": ",",
                "rowDelimiter": "\n"
            },
            "compression": {
                "type": "GZip",
                "level": "Optimal"
            }
        }
    }
}

Copy activity properties

For a full list of sections and properties available for defining activities, see the Pipelines article. This section provides a list of properties supported by the Blob storage source and sink.

Blob storage as a source type

To copy data from Blob storage, set the source type in the copy activity to BlobSource. The following properties are supported in the copy activity source section.

Example:

"activities":[
    {
        "name": "CopyFromBlob",
        "type": "Copy",
        "inputs": [
            {
                "referenceName": "<Azure Blob input dataset name>",
                "type": "DatasetReference"
            }
        ],
        "outputs": [
            {
                "referenceName": "<output dataset name>",
                "type": "DatasetReference"
            }
        ],
        "typeProperties": {
            "source": {
                "type": "BlobSource",
                "recursive": true
            },
            "sink": {
                "type": "<sink type>"
            }
        }
    }
]

Blob storage as a sink type

To copy data to Blob storage, set the sink type in the copy activity to BlobSink. The following properties are supported in the sink section.

Example:

"activities":[
    {
        "name": "CopyToBlob",
        "type": "Copy",
        "inputs": [
            {
                "referenceName": "<input dataset name>",
                "type": "DatasetReference"
            }
        ],
        "outputs": [
            {
                "referenceName": "<Azure Blob output dataset name>",
                "type": "DatasetReference"
            }
        ],
        "typeProperties": {
            "source": {
                "type": "<source type>"
            },
            "sink": {
                "type": "BlobSink",
                "copyBehavior": "PreserveHierarchy"
            }
        }
    }
]

Some recursive and copyBehavior examples

This section describes the resulting behavior of the Copy operation for different combinations of recursive and copyBehavior values.

Next steps

For a list of data stores supported as sources and sinks by the copy activity in Data Factory, see Supported data stores.