> For the complete documentation index, see [llms.txt](https://brightercommand.gitbook.io/paramore-brighter-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://brightercommand.gitbook.io/paramore-brighter-documentation/outbox-and-inbox/distributedlock/azureblobdistributedlock.md).

# Azure Blob Distributed Lock

The Azure Blob locking provider implements Brighter's [distributed lock](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md) using **blob leases** in Azure Blob Storage, so a single [Outbox Sweeper](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport.md#implicit-clear) and Archiver run when you scale out. It is a good choice when your workloads already run on Azure.

## Package

* **Paramore.Brighter.Locking.Azure**

The provider takes a lease on a blob inside a container that you must create in advance — see [Provisioning](#provisioning).

## Configuration

Configure the provider with `AzureBlobLockingProvider`, passing an `AzureBlobLockingProviderOptions`. The options constructor takes the container URI and a `TokenCredential`:

```csharp
new AzureBlobLockingProvider(
    new AzureBlobLockingProviderOptions(
        blobContainerUri: new Uri("https://myaccount.blob.core.windows.net/brighter-locks"),
        tokenCredential: new DefaultAzureCredential()));
```

| Setting               | Type                   | Default                          | Description                                                                                                   |
| --------------------- | ---------------------- | -------------------------------- | ------------------------------------------------------------------------------------------------------------- |
| `BlobContainerUri`    | `Uri`                  | *(required)*                     | The URI of the blob container that holds the lock blobs.                                                      |
| `TokenCredential`     | `TokenCredential`      | *(required)*                     | The Azure credential used to authenticate, for example `DefaultAzureCredential`.                              |
| `LeaseValidity`       | `TimeSpan`             | 1 minute                         | How long the blob lease is held before it expires automatically. Set it longer than a Sweeper/Archiver cycle. |
| `StorageLocationFunc` | `Func<string, string>` | `resource => $"lock-{resource}"` | Maps a resource name to the blob name used for its lock.                                                      |

## Example

```csharp
services
    .AddBrighter()
    .AddProducers(opt =>
    {
        opt.Outbox = /* your external Outbox */;
        // ... connection/transaction providers for your Outbox ...

        opt.DistributedLock = new AzureBlobLockingProvider(
            new AzureBlobLockingProviderOptions(
                new Uri("https://myaccount.blob.core.windows.net/brighter-locks"),
                new DefaultAzureCredential())
            {
                LeaseValidity = TimeSpan.FromMinutes(2)
            });
    })
    .UseOutboxSweeper(opt => { opt.BatchSize = 10; });
```

## Provisioning

Create the blob container referenced by `BlobContainerUri` before the provider runs. The provider creates the per-resource lock blobs (named by `StorageLocationFunc`) inside that container as needed; it does not create the container itself. Grant the `TokenCredential` permission to read, write, and lease blobs in the container.

## Notes

* Keep `LeaseValidity` longer than a typical Sweeper or Archiver batch so the lease does not expire mid-run. See [Lease Expiry vs Manual Release](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md#lease-expiry-vs-manual-release).
* If the holding instance crashes, the blob lease expires after `LeaseValidity` and another instance can take over on a later cycle.

## Further Reading

* [Distributed Lock](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md) — concepts and the full provider list
* [Outbox Support](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport.md) — the Sweeper and Archiver


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