Structured Logger Generator

Creates structured logging infrastructure for observability and request tracing.

When to Use

Scenario	Example
Distributed tracing	Correlate logs across microservices
Request debugging	Track full request lifecycle
Audit logging	Structured records with context
Error investigation	Rich context in error logs

Component Characteristics

CorrelationId

• Value Object wrapping UUIDv4
• Immutable, self-validating
• Propagated via X-Request-ID header

CorrelationIdProcessor

• Monolog processor adding correlation_id to every record
• Reads from CorrelationIdHolder thread-local storage
• Zero-config: auto-enriches all log entries

RequestContextProcessor

• Monolog processor adding request metadata
• Captures method, URI, IP, user-agent
• Enables filtering logs by request attributes

CorrelationIdMiddleware

• PSR-15 middleware extracting or generating X-Request-ID
• Stores in CorrelationIdHolder for downstream use
• Adds correlation ID to response headers

CorrelationIdHolder

• Static thread-local storage for correlation ID
• Set once per request, available globally
• Reset after request completes

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Generation Process

Step 1: Generate Core Components

Path: src/Infrastructure/Logging/

1. CorrelationId.php — Value Object with UUID validation
2. CorrelationIdHolder.php — Thread-local correlation ID storage

Step 2: Generate Monolog Processors

Path: src/Infrastructure/Logging/Processor/

1. CorrelationIdProcessor.php — Adds correlation_id to log records
2. RequestContextProcessor.php — Adds request context to log records

Step 3: Generate Middleware

Path: src/Infrastructure/Logging/

1. CorrelationIdMiddleware.php — PSR-15 middleware for correlation ID

Step 4: Generate Tests

1. CorrelationIdTest.php — Value Object tests
2. CorrelationIdProcessorTest.php — Processor enrichment tests
3. CorrelationIdMiddlewareTest.php — Middleware behavior tests

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File Placement

Component	Path
Core Classes	src/Infrastructure/Logging/
Processors	src/Infrastructure/Logging/Processor/
Unit Tests	tests/Unit/Infrastructure/Logging/

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Naming Conventions

Component	Pattern	Example
Value Object	CorrelationId	CorrelationId
Holder	CorrelationIdHolder	CorrelationIdHolder
Processor	{Context}Processor	CorrelationIdProcessor
Middleware	CorrelationIdMiddleware	CorrelationIdMiddleware
Test	{ClassName}Test	CorrelationIdTest

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Quick Template Reference

CorrelationId

final readonly class CorrelationId
{
    public function __construct(public string $value)
    {
        // Validates UUID v4 format
    }

    public static function generate(): self;
    public function toString(): string;
}

CorrelationIdProcessor

final readonly class CorrelationIdProcessor
{
    public function __invoke(LogRecord $record): LogRecord;
}

CorrelationIdMiddleware

final readonly class CorrelationIdMiddleware implements MiddlewareInterface
{
    public function process(
        ServerRequestInterface $request,
        RequestHandlerInterface $handler
    ): ResponseInterface;
}

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Usage Example

// Middleware extracts or generates correlation ID
$middleware = new CorrelationIdMiddleware(headerName: 'X-Request-ID');

// Monolog processor auto-enriches every log entry
$logger->pushProcessor(new CorrelationIdProcessor());
$logger->pushProcessor(new RequestContextProcessor($request));

// Log entry output:
// {"message":"Order created","correlation_id":"550e8400-...","method":"POST","uri":"/orders"}

---

Log Flow

Request ──→ CorrelationIdMiddleware
                │
         Extract/Generate X-Request-ID
                │
         Store in CorrelationIdHolder
                │
         CorrelationIdProcessor ──→ Adds correlation_id to every log
         RequestContextProcessor ──→ Adds method, URI, IP to every log
                │
         Response ──→ Add X-Request-ID header

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Anti-patterns to Avoid

Anti-pattern	Problem	Solution
Manual correlation IDs	Inconsistent, easy to forget	Auto-enrich via processor
Unstructured logs	Cannot query or filter	Use structured JSON format
No request context	Cannot trace request flow	Add request processor
Global mutable logger	Thread safety issues	Use holder with request scope
Missing response header	Client cannot correlate	Return X-Request-ID in response
No holder cleanup	Memory leak between requests	Reset holder after request

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References

For complete PHP templates and examples, see:

• references/templates.md — CorrelationId, Processors, Middleware, Holder templates
• references/examples.md — Service integration examples and tests