> 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/dynamodbdistributedlock.md).

# DynamoDB Distributed Lock

The DynamoDB locking provider implements Brighter's distributed lock on top of Amazon DynamoDB, so a single Outbox Sweeper and Archiver run when you scale out.

> **Reference** · Applies to **Brighter V10**

The DynamoDB locking provider implements Brighter's [distributed lock](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md) on top of Amazon DynamoDB, 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 natural fit when you already use the [DynamoDB Outbox](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport/dynamooutbox.md).

## DynamoDB Distributed Lock Package

Add the locking package for AWS SDK v4:

* **Paramore.Brighter.Locking.DynamoDB.V4**

Prefer the **V4** package for new projects. The earlier `Paramore.Brighter.Locking.DynamoDB` package targets AWS SDK v3, which is out of support on AWS, and exists only to aid migration.

The provider stores its locks in a DynamoDB table that you must create in advance (see [Provisioning](#dynamodb-distributed-lock-provisioning)).

## DynamoDB Distributed Lock Configuration

Configure the provider with `DynamoDbLockingProvider`, passing your `IAmazonDynamoDB` client and a `DynamoDbLockingProviderOptions`:

```csharp
using Paramore.Brighter.Locking.DynamoDB.V4;

new DynamoDbLockingProvider(
    dynamoDb,
    new DynamoDbLockingProviderOptions(
        lockTableName: "brighter-locks",
        leaseholderGroupId: "sweeper-group"));
```

`DynamoDbLockingProviderOptions` takes two required values in its constructor and exposes two optional settings:

| Option                | Type       | Default    | Description                                                                                                     |
| --------------------- | ---------- | ---------- | --------------------------------------------------------------------------------------------------------------- |
| `LockTableName`       | `string`   | `none`     | Names the DynamoDB table that holds the locks.                                                                  |
| `LeaseholderGroupId`  | `string`   | `none`     | Identifies the group of instances that share the lock; every instance that must coordinate uses the same value. |
| `LeaseValidity`       | `TimeSpan` | `60000 ms` | How long the lease is held before it expires automatically.                                                     |
| `ManuallyReleaseLock` | `bool`     | `false`    | Whether the provider releases the lock on completion rather than letting it expire.                             |

Both constructor parameters are required, and both properties are `init`-only: set them in the constructor call or in an object initialiser, not afterwards. Set `LeaseValidity` comfortably longer than a Sweeper or Archiver cycle.

## DynamoDB Distributed Lock Example

```csharp
using System;
using Amazon.DynamoDBv2;
using Microsoft.Extensions.DependencyInjection;
using Paramore.Brighter.DynamoDb.V4;
using Paramore.Brighter.Extensions.DependencyInjection;
using Paramore.Brighter.Locking.DynamoDB.V4;
using Paramore.Brighter.Outbox.DynamoDB.V4;
using Paramore.Brighter.Outbox.Hosting;

var dynamoDb = new AmazonDynamoDBClient();

services
    .AddSingleton<IAmazonDynamoDB>(dynamoDb)
    .AddBrighter()
    .AddProducers(opt =>
    {
        opt.Outbox = new DynamoDbOutbox(dynamoDb, new DynamoDbConfiguration { /* ... */ });
        opt.ConnectionProvider = typeof(DynamoDbUnitOfWork);
        opt.TransactionProvider = typeof(DynamoDbUnitOfWork);

        opt.DistributedLock = new DynamoDbLockingProvider(
            dynamoDb,
            new DynamoDbLockingProviderOptions("brighter-locks", "sweeper-group")
            {
                LeaseValidity = TimeSpan.FromMinutes(2)
            });
    })
    .UseOutboxSweeper(opt => { opt.BatchSize = 10; });
```

## DynamoDB Distributed Lock Provisioning

The lock table must exist before the provider runs. Create a table whose partition key matches the provider's lock items, with the name you pass as `LockTableName`. If you already provision a DynamoDB Outbox table, provision the lock table the same way (for example with the AWS SDK, CDK, or Terraform). Consider enabling DynamoDB's [time-to-live](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html) feature so expired lock items are cleaned up automatically.

## DynamoDB Distributed Lock Notes

* Use the same `LeaseholderGroupId` for every instance that must share the lock; a different value creates an independent lock.
* 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).

## Further Reading

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


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