README

Overview

Nexus\Idempotency is a Layer 1 package for command-level idempotency: deduplicate mutating operations using a tenant-scoped composite key (tenantId, operationRef, clientKey) plus a request fingerprint, and replay a stored opaque result for safe retries.

It does not implement HTTP, databases, outbox, event streams, or audit trails—see REQUIREMENTS.md for boundaries.

Architecture

• Layer 1: pure PHP 8.3+, framework-agnostic
• Explicit lifecycle: begin() → domain work → complete() or fail()
• Persistence via IdempotencyStoreInterface (composite of IdempotencyQueryInterface + IdempotencyPersistInterface; e.g. InMemoryIdempotencyStore for tests — uses JSON-encoded tuple keys json_encode([tenantId, operationRef, clientKey]) so segments cannot collide across delimiter characters)
• Time via IdempotencyClockInterface (SystemClock returns UTC DateTimeImmutable, or test doubles)

Key interfaces

• Nexus\Idempotency\Contracts\IdempotencyServiceInterface
• Nexus\Idempotency\Contracts\IdempotencyStoreInterface (extends query + persist ports)
• Nexus\Idempotency\Contracts\IdempotencyClockInterface

Installation

From monorepo root:

composer dump-autoload
vendor/bin/phpunit -c packages/Idempotency/phpunit.xml

Usage (conceptual)

$service = new IdempotencyService($store, $store, $clock, IdempotencyPolicy::default());

$decision = $service->begin($tenantId, $operationRef, $clientKey, $fingerprint);

if ($decision->outcome === BeginOutcome::Replay) {
    return $decision->replayResult; // replay cached outcome
}

if ($decision->outcome === BeginOutcome::InProgress) {
    // Another in-flight execution for the same key + fingerprint; surface 409 + Retry-After in Layer 3.
    return;
}

// BeginOutcome::FirstExecution — run domain command, then complete using the attempt bound to this reservation:
$service->complete(
    $tenantId,
    $operationRef,
    $clientKey,
    $fingerprint,
    $decision->record->attemptToken,
    new ResultEnvelope($json),
);

complete() / fail() require the AttemptToken from the FirstExecution record for that attempt so completions cannot attach to a superseded reservation after TTL expiry/replace.

License

MIT