> 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/brighterinboxsupport/spannerinbox.md).

# Spanner Inbox

The Spanner Inbox records the messages a consumer has already handled in a Google Cloud Spanner table, so a redelivery is recognised rather than reprocessed.

> **Reference** · Applies to **Brighter V10** · Prerequisites: [Inbox Support](/paramore-brighter-documentation/outbox-and-inbox/brighterinboxsupport.md)

The Spanner Inbox records the messages a consumer has already handled in a Google Cloud Spanner table, so a redelivery is recognised rather than reprocessed. It is configured entirely through the shared relational configuration.

## Spanner Inbox Configuration

```powershell
dotnet add package Paramore.Brighter.Inbox.Spanner
dotnet add package Paramore.Brighter.Spanner
```

**The class is `SpannerInboxAsync`, and there is no synchronous twin.** It implements Brighter's inbox interfaces through `RelationalDatabaseInbox`, so it is used exactly like any other Inbox; only the name is different.

```csharp
using Microsoft.Extensions.DependencyInjection;
using Paramore.Brighter;
using Paramore.Brighter.Inbox;
using Paramore.Brighter.Inbox.Spanner;
using Paramore.Brighter.ServiceActivator.Extensions.DependencyInjection;

public static class SpannerInboxRegistration
{
    public static void ConfigureServices(IServiceCollection services)
    {
        var configuration = new RelationalDatabaseConfiguration(
            connectionString: "Data Source=projects/my-project/instances/my-instance/databases/brighter",
            inboxTableName: "Inbox");

        services.AddSingleton<IAmARelationalDatabaseConfiguration>(configuration);

        services.AddConsumers(options =>
        {
            options.InboxConfiguration = new InboxConfiguration(
                new SpannerInboxAsync(configuration),
                scope: InboxScope.Commands,
                onceOnly: true,
                actionOnExists: OnceOnlyAction.Warn);
            // ... your subscriptions and channel factory
        });
    }
}
```

Constructed with the configuration alone, `SpannerInboxAsync` builds its own `SpannerConnectionProvider`; a second constructor takes an `IAmARelationalDbConnectionProvider` when you want to share one.

## Spanner Inbox Options

**The Spanner Inbox has no options type of its own.** It takes an `IAmARelationalDatabaseConfiguration`, the type every relational Outbox, Inbox, provisioner and queue-table transport takes, and its options are documented once at [Relational Database Configuration Reference](/paramore-brighter-documentation/brighter-configuration/brighterbasicconfiguration/relationaldatabaseconfigurationreference.md#relational-database-configuration-options). That is why this page has no table: there is no Spanner Inbox surface to tabulate.

The option that matters here is **`inboxTableName`**, which defaults to `Inbox`. Note the asymmetry the reference page records — the constructor parameter is `inboxTableName` and the property you read back is `InBoxTableName`, with a capital `B`.

`schemaName` is not used: Spanner does not organise tables into schemas the way the other relational backends do, and its provisioning extensions take no `schemaName` argument.

## Provisioning the Spanner Inbox

You have the same two options every relational Inbox has.

**Option A — let Brighter provision it.** `AddSpannerInbox` registers a provisioner that creates the table at startup; see [Configuring Box Provisioning](/paramore-brighter-documentation/outbox-and-inbox/boxprovisioning/boxprovisioningconfiguration.md#spanner). Spanner uses the **degenerate runner** — it creates the table on a fresh database and cannot evolve an existing one, so an Inbox table created by an earlier Brighter release needs its new columns added by hand. See [Per-backend differences to be aware of](/paramore-brighter-documentation/outbox-and-inbox/boxprovisioning.md#per-backend-differences-to-be-aware-of), and [Replay On Seen Reference](/paramore-brighter-documentation/outbox-and-inbox/replayonseen/replayonseenreference.md) for the causation column that [replay on seen](/paramore-brighter-documentation/outbox-and-inbox/replayonseen.md) needs on both boxes.

**Option B — manage the DDL yourself.** `SpannerInboxBuilder.GetDDL()` returns the DDL Brighter ships:

```csharp
using Paramore.Brighter.Inbox.Spanner;

public static class SpannerInboxDdl
{
    public static string Ddl() => SpannerInboxBuilder.GetDDL("Inbox");
}
```

The table is keyed on `(CommandId, ContextKey)`, so the same command handled by two different handlers is two rows rather than a collision:

```sql
CREATE TABLE IF NOT EXISTS `Inbox`(
    `CommandId` STRING(256) NOT NULL,
    `CommandType` STRING(256),
    `CommandBody` JSON,
    `Timestamp` TIMESTAMP,
    `ContextKey` STRING(256)
) PRIMARY KEY (`CommandId`, `ContextKey`)
```

Duplicate inserts surface as a `SpannerException` carrying an `AlreadyExists` status, which the Inbox translates into the `OnceOnlyAction` you configured.

## Further Reading

* [Inbox Support](/paramore-brighter-documentation/outbox-and-inbox/brighterinboxsupport.md) — what an Inbox is for and when you need one
* [Relational Database Configuration Reference](/paramore-brighter-documentation/brighter-configuration/brighterbasicconfiguration/relationaldatabaseconfigurationreference.md) — every option this Inbox takes
* [Spanner Outbox](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport/spanneroutbox.md) — the same configuration type, one family over
* [Database Provisioning](/paramore-brighter-documentation/outbox-and-inbox/boxprovisioning.md) — the migration machinery, and why Spanner's runner is degenerate
* [Dispatcher Configuration Reference](/paramore-brighter-documentation/brighter-configuration/brighterbasicconfiguration/dispatcherconfigurationreference.md#inbox) — where `InboxConfiguration` fits


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