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Custom Storage Drivers

Chronicle resolves persistence through a configurable StorageDriver. You can register a custom backend - an external audit service, an object store, a secondary database - without changing any Chronicle internals.

The contract​

interface StorageDriver
{
    public function store(array $entry): Entry;
}

store() receives the fully-built, validated, canonicalized, and chain-hashed entry attributes and must:

  1. Persist them
  2. Return a hydrated Chronicle\Entry\Entry model that reflects exactly what was stored - no field may be silently altered

Implementation​

use Chronicle\Contracts\StorageDriver;
use Chronicle\Entry\Entry;

class AuditServiceDriver implements StorageDriver
{
    public function __construct(
        private readonly AuditServiceClient $client,
    ) {}

    public function store(array $entry): Entry
    {
        // Persist to external service
        $this->client->send($entry);

        // Return a hydrated Entry model
        $model = new Entry;
        $model->forceFill($entry);
        $model->exists = true;

        return $model;
    }
}

Registering a custom driver​

Register via Chronicle::extendDriver() in a service provider:

use Chronicle\Facades\Chronicle;

class AppServiceProvider extends ServiceProvider
{
    public function boot(): void
    {
        Chronicle::extendDriver('audit-service', function (): AuditServiceDriver {
            return new AuditServiceDriver(
                app(AuditServiceClient::class)
            );
        });
    }
}

Then select it in your environment:

CHRONICLE_DRIVER=audit-service

Registration constraints​

Reserved names - these driver names cannot be registered or overridden:

  • eloquent
  • database
  • queued
  • array
  • null

Attempting to register a reserved name throws InvalidArgumentException.

Single registration - each custom driver name can only be registered once. Registering the same name a second time throws InvalidArgumentException.

Statelessness requirement​

Drivers must be stateless. Each store() call is independent - do not accumulate state between calls. Chronicle may construct or resolve the driver multiple times during a request lifetime, and in a queued setup the driver runs inside a separate job process.

See also​