Rate Limiter Generator

Creates Rate Limiter pattern infrastructure for request throttling and API protection.

When to Use

Scenario	Example
API protection	Prevent abuse
Resource throttling	Database connection limits
Fair usage	Per-user request limits
Burst protection	Spike handling

Component Characteristics

RateLimiterInterface

• Common interface for all algorithms
• Check and consume methods
• Remaining capacity queries

Algorithms

• Token Bucket: Smooth rate limiting with burst capacity
• Sliding Window: Time-based with sliding window log
• Fixed Window: Simple time-based counter

RateLimitResult

• Contains allowed/denied status
• Provides retry-after information
• Generates HTTP headers

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Generation Process

Step 1: Generate Core Components

Path: src/Infrastructure/Resilience/RateLimiter/

1. RateLimiterInterface.php — Common interface
2. RateLimitResult.php — Result value object with headers
3. RateLimitExceededException.php — Exception with retry info
4. StorageInterface.php — Storage abstraction

Step 2: Choose and Generate Algorithm

Choose based on use case:

1. TokenBucketRateLimiter.php — For APIs with burst allowance
2. SlidingWindowRateLimiter.php — For strict per-time limits
3. FixedWindowRateLimiter.php — For simple rate limiting

Step 3: Generate Storage

1. RedisStorage.php — Production storage with TTL

Step 4: Generate Tests

1. {Algorithm}RateLimiterTest.php — Algorithm tests
2. RateLimitResultTest.php — Result value object tests

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File Placement

Component	Path
All Classes	src/Infrastructure/Resilience/RateLimiter/
Unit Tests	tests/Unit/Infrastructure/Resilience/RateLimiter/

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Naming Conventions

Component	Pattern	Example
Interface	RateLimiterInterface	RateLimiterInterface
Token Bucket	TokenBucketRateLimiter	TokenBucketRateLimiter
Sliding Window	SlidingWindowRateLimiter	SlidingWindowRateLimiter
Fixed Window	FixedWindowRateLimiter	FixedWindowRateLimiter
Result	RateLimitResult	RateLimitResult
Exception	RateLimitExceededException	RateLimitExceededException
Test	{ClassName}Test	TokenBucketRateLimiterTest

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Quick Template Reference

RateLimiterInterface

interface RateLimiterInterface
{
    public function attempt(string $key, int $tokens = 1): RateLimitResult;
    public function getRemainingTokens(string $key): int;
    public function getRetryAfter(string $key): ?int;
    public function reset(string $key): void;
}

RateLimitResult

final readonly class RateLimitResult
{
    public static function allowed(int $remaining, int $limit, \DateTimeImmutable $resetsAt): self;
    public static function denied(int $limit, int $retryAfter, \DateTimeImmutable $resetsAt): self;
    public function isAllowed(): bool;
    public function isDenied(): bool;
    public function toHeaders(): array; // X-RateLimit-* headers
}

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Usage Example

// Create limiter
$limiter = new TokenBucketRateLimiter(
    capacity: 100,
    refillRate: 10.0, // 10 tokens per second
    clock: $clock,
    storage: new RedisStorage($redis)
);

// Check limit
$result = $limiter->attempt('user:123');

if ($result->isDenied()) {
    throw new RateLimitExceededException(
        key: 'user:123',
        limit: $result->limit,
        retryAfterSeconds: $result->retryAfterSeconds
    );
}

// Add headers to response
foreach ($result->toHeaders() as $name => $value) {
    $response = $response->withHeader($name, (string) $value);
}

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Algorithm Comparison

Algorithm	Burst Handling	Memory	Precision	Use Case
Token Bucket	Good (configurable)	Low	Medium	APIs with burst allowance
Sliding Window	Limited	High	High	Strict per-time limits
Fixed Window	Poor (boundary issues)	Low	Low	Simple rate limiting

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Anti-patterns to Avoid

Anti-pattern	Problem	Solution
No Redis/Shared Storage	Per-instance limits	Use shared storage
Missing Headers	Client can't adapt	Return X-RateLimit-* headers
Single Algorithm	Doesn't fit all cases	Choose per use case
No Retry-After	Client spams	Always return retry timing
Synchronous Blocking	Thread blocking	Use non-blocking check

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References

For complete PHP templates and examples, see:

• references/templates.md — All algorithm implementations
• references/examples.md — Middleware example and tests