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Create and manage blob leases with Python

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This article shows how to create and manage blob leases using the Azure Storage client library for Python. You can use the client library to acquire, renew, release, and break blob leases.

To learn about leasing a blob using asynchronous APIs, see Lease blobs asynchronously.

Prerequisites

  • This article assumes you already have a project set up to work with the Azure Blob Storage client library for Python. To learn about setting up your project, including package installation, adding import statements, and creating an authorized client object, see Get started with Azure Blob Storage and Python.
  • The authorization mechanism must have permissions to work with a blob lease. To learn more, see the authorization guidance for the following REST API operation:

About blob leases

A lease creates and manages a lock on a blob for write and delete operations. The lock duration can be 15 to 60 seconds, or can be infinite. A lease on a blob provides exclusive write and delete access to the blob. To write to a blob with an active lease, a client must include the active lease ID with the write request.

To learn more about lease states and when you can perform a given action on a lease, see Lease states and actions.

All container operations are permitted on a container that includes blobs with an active lease, including Delete Container. Therefore, a container may be deleted even if blobs within it have active leases. Use the Lease Container operation to control rights to delete a container.

Lease operations are handled by the BlobLeaseClient class, which provides a client containing all lease operations for blobs and containers. To learn more about container leases using the client library, see Create and manage container leases with Python.

Acquire a lease

When you acquire a blob lease, you obtain a lease ID that your code can use to operate on the blob. If the blob already has an active lease, you can only request a new lease by using the active lease ID. However, you can specify a new lease duration.

To acquire a lease, create an instance of the BlobLeaseClient class, and then use the following method:

You can also acquire a lease on a blob by creating an instance of BlobClient, and using the following method:

The following example acquires a 30-second lease for a blob:

def acquire_blob_lease(self, blob_service_client: BlobServiceClient, container_name):
    # Instantiate a BlobClient
    blob_client = blob_service_client.get_blob_client(container=container_name, blob="sample-blob.txt")

    # Acquire a 30-second lease on the blob
    lease_client = blob_client.acquire_lease(30)

    return lease_client

Renew a lease

You can renew a blob lease if the lease ID specified on the request matches the lease ID associated with the blob. The lease can be renewed even if it has expired, as long as the blob hasn't been modified or leased again since the expiration of that lease. When you renew a lease, the duration of the lease resets.

To renew a lease, use the following method:

The following example renews a lease for a blob:

def renew_blob_lease(self, lease_client: BlobLeaseClient):
    # Renew a lease on a blob
    lease_client.renew()

Release a lease

You can release a blob lease if the lease ID specified on the request matches the lease ID associated with the blob. Releasing a lease allows another client to acquire a lease for the blob immediately after the release is complete.

You can release a lease by using the following method:

The following example releases the lease on a blob:

def release_blob_lease(self, lease_client: BlobLeaseClient):
    # Release a lease on a blob
    lease_client.release()

Break a lease

You can break a blob lease if the blob has an active lease. Any authorized request can break the lease; the request isn't required to specify a matching lease ID. A lease can't be renewed after it's broken, and breaking a lease prevents a new lease from being acquired for a period of time until the original lease expires or is released.

You can break a lease by using the following method:

The following example breaks the lease on a blob:

def break_blob_lease(self, lease_client: BlobLeaseClient):
    # Break a lease on a blob
    lease_client.break_lease()

Lease blobs asynchronously

The Azure Blob Storage client library for Python supports leasing blobs asynchronously. To learn more about project setup requirements, see Asynchronous programming.

Follow these steps to lease a blob using asynchronous APIs:

  1. Add the following import statements:

    import asyncio

from azure.identity.aio import DefaultAzureCredential
from azure.storage.blob.aio import BlobServiceClient, BlobLeaseClient

  2. Add code to run the program using asyncio.run. This function runs the passed coroutine, main() in our example, and manages the asyncio event loop. Coroutines are declared with the async/await syntax. In this example, the main() coroutine first creates the top level BlobServiceClient using async with, then calls the method that acquires the blob lease. Note that only the top level client needs to use async with, as other clients created from it share the same connection pool.

    async def main():
    sample = BlobSamples()

    # TODO: Replace <storage-account-name> with your actual storage account name
    account_url = "https://<storage-account-name>.blob.core.windows.net"
    credential = DefaultAzureCredential()

    async with BlobServiceClient(account_url, credential=credential) as blob_service_client:
        lease_client = await sample.acquire_blob_lease(blob_service_client, "sample-container")

if __name__ == '__main__':
    asyncio.run(main())

  3. Add code to acquire a blob lease. The code is the same as the synchronous example, except that the method is declared with the async keyword and the await keyword is used when calling the acquire_lease method.

    async def acquire_blob_lease(self, blob_service_client: BlobServiceClient, container_name):
    # Instantiate a BlobClient
    blob_client = blob_service_client.get_blob_client(container=container_name, blob="sample-blob.txt")

    # Acquire a 30-second lease on the blob
    lease_client = await blob_client.acquire_lease(30)

    return lease_client

With this basic setup in place, you can implement other examples in this article as coroutines using async/await syntax.

Lease states and actions

The following diagram shows the five states of a lease, and the commands or events that cause lease state changes.

A diagram showing blob lease states and state change triggers.

The following table lists the five lease states, gives a brief description of each, and lists the lease actions allowed in a given state. These lease actions cause state transitions, as shown in the diagram.

Lease state Description Lease actions allowed
Available The lease is unlocked and can be acquired. acquire
Leased The lease is locked. acquire (same lease ID only), renew, change, release, and break
Expired The lease duration has expired. acquire, renew, release, and break
Breaking The lease has been broken, but the lease will continue to be locked until the break period has expired. release and break
Broken The lease has been broken, and the break period has expired. acquire, release, and break

When a lease expires, the lease ID is maintained by the Blob service until the blob is modified or leased again. A client may attempt to renew or release the lease using the expired lease ID. If this operation is successful, the client knows that the blob hasn't been changed since the lease ID was last valid. If the request fails, the client knows that the blob was modified, or the blob was leased again since the lease was last active. The client must then acquire a new lease on the blob.

If a lease expires rather than being explicitly released, a client may need to wait up to one minute before a new lease can be acquired for the blob. However, the client can renew the lease with their lease ID immediately if the blob hasn't been modified.

A lease can't be granted for a blob snapshot, since snapshots are read-only. Requesting a lease against a snapshot results in status code 400 (Bad Request).

Resources

To learn more about managing blob leases using the Azure Blob Storage client library for Python, see the following resources.

REST API operations

The Azure SDK for Python contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar Python paradigms. The client library methods for managing blob leases use the following REST API operation:

Code samples

Client library resources

See also