Saga Pattern Generator

Saga Pattern Generator

Creates Saga pattern infrastructure for distributed transaction coordination.

When to Use

• Distributed transactions across multiple services
• Long-running business processes
• Operations requiring compensation on failure
• Multi-step workflows with rollback capability

Component Characteristics

SagaState Enum

• Domain layer enum
• Defines saga lifecycle states: Pending, Running, Compensating, Completed, Failed, CompensationFailed
• Includes state transition validation
• Terminal states detection

SagaStep Interface

• Domain layer interface
• Execute and compensate methods
• Idempotency declaration
• Timeout configuration

SagaContext

• Carries saga execution data
• Serializable for persistence
• Supports data accumulation across steps

SagaOrchestrator

• Application layer coordinator
• Manages step execution
• Handles compensation flow (reverse order)
• Persists state after each step

SagaPersistence

• Stores saga state for recovery
• Supports finding incomplete sagas
• Dead letter handling

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Generation Process

Step 1: Analyze Request

Determine:

• Context name (Order, Payment, Shipping)
• Required saga steps
• Compensation logic for each step

Step 2: Generate Core Components

Create in this order:

1. Domain Layer (src/​Domain/​Shared/​Saga/)

   • SagaState.php — State enum with transitions
   • StepResult.php — Step result value object
   • SagaStepInterface.php — Step contract
   • SagaContext.php — Execution context
   • SagaResult.php — Saga result
   • Exception classes

2. Application Layer (src/​Application/​Shared/​Saga/)

   • SagaPersistenceInterface.php — Persistence port
   • SagaRecord.php — Persisted record
   • AbstractSagaStep.php — Base step class
   • SagaOrchestrator.php — Orchestrator

3. Infrastructure Layer

   • DoctrineSagaPersistence.php — Doctrine implementation
   • Database migration

4. Tests

   • SagaStateTest.php
   • SagaOrchestratorTest.php

Step 3: Generate Context-Specific Steps

For each saga step (e.g., Order saga):

src/​Application/​{Context}/​Saga/​Step/
├── ReserveInventoryStep.php
├── ChargePaymentStep.php
└── CreateShipmentStep.php

src/​Application/​{Context}/​Saga/
└── {Context}SagaFactory.php

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File Placement

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Key Principles

Compensation Rules

1. Compensate in reverse order of execution
2. Compensations must be idempotent
3. Handle "already compensated" gracefully
4. Log all compensation attempts

Idempotency

1. Use idempotency keys for each step
2. Check for existing results before executing
3. Return existing result if found

State Transitions

Pending → Running → Completed
              ↓
         Compensating → Failed
              ↓
         CompensationFailed

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Naming Conventions

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Quick Template Reference

SagaStepInterface

interface SagaStepInterface
{
    public function name(): string;
    public function execute(SagaContext $context): StepResult;
    public function compensate(SagaContext $context): StepResult;
    public function isIdempotent(): bool;
    public function timeout(): int;
}

StepResult

final readonly class StepResult
{
    public static function success(array $data = []): self;
    public static function failure(string $error): self;
    public function isSuccess(): bool;
    public function isFailure(): bool;
}

Concrete Step Pattern

final readonly class {Action}Step extends AbstractSagaStep
{
    public function name(): string
    {
        return '{action_name}';
    }

    public function execute(SagaContext $context): StepResult
    {
        $idempotencyKey = $this->idempotencyKey($context);

        // Check for existing result (idempotency)
        // Execute action
        // Return StepResult::success([...data...]) or failure
    }

    public function compensate(SagaContext $context): StepResult
    {
        // Get data from context
        // Undo action
        // Handle "already undone" gracefully
        return StepResult::success();
    }
}

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Usage Example

// Create saga
$saga = $orderSagaFactory->create($command);

// Execute
$result = $saga->execute();

if ($result->isCompleted()) {
    // Success
} elseif ($result->isFailed()) {
    // Failed but compensated
    $error = $result->error;
} elseif ($result->isCompensationFailed()) {
    // Needs manual intervention
    $originalError = $result->error;
    $compensationError = $result->compensationError;
}

---

DI Configuration

# Symfony services.yaml
Domain\Shared\Saga\SagaStepInterface:
    tags: ['saga.step']

Application\Shared\Saga\SagaPersistenceInterface:
    alias: Infrastructure\Persistence\Doctrine\Repository\DoctrineSagaPersistence

Application\Order\Saga\OrderSagaFactory:
    arguments:
        $reserveStep: '@Application\Order\Saga\Step\ReserveInventoryStep'
        $chargeStep: '@Application\Order\Saga\Step\ChargePaymentStep'
        $shipStep: '@Application\Order\Saga\Step\CreateShipmentStep'

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Database Schema

CREATE TABLE sagas (
    id VARCHAR(255) PRIMARY KEY,
    type VARCHAR(255) NOT NULL,
    state VARCHAR(50) NOT NULL,
    completed_steps JSONB NOT NULL DEFAULT '[]',
    context JSONB NOT NULL,
    error TEXT,
    created_at TIMESTAMP(6) NOT NULL,
    updated_at TIMESTAMP(6) NOT NULL,
    completed_at TIMESTAMP(6)
);

CREATE INDEX idx_sagas_state ON sagas (state);
CREATE INDEX idx_sagas_type_state ON sagas (type, state);

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References

For complete PHP templates and test examples, see:

• references/​templates.md — All component templates
• references/​examples.md — Order saga example and unit tests