Getting Started

WARNING

Very Early Work in Progress — This library is under active development and not yet production-ready. APIs will change, many implementations are stubs, and test coverage is incomplete. Use at your own risk, contributions welcome.

Installation

composer require clegginabox/airlock

Some Seal implementations require PHP extensions that are only available in certain environments:

Extension	Required by	Notes
ext-redis	Redis-backed queues and stores	Docker-only locally
ext-memcached	Memcached lock stores	Docker-only locally
ext-zookeeper	ZooKeeper lock stores	Docker-only locally

If installing locally without these extensions:

composer require clegginabox/airlock --ignore-platform-reqs

Quick Example

Protect an endpoint from the hug of death — cap concurrent access, reject the rest:

use Clegginabox\Airlock\Bridge\Symfony\Seal\SymfonySemaphoreSeal;
use Clegginabox\Airlock\OpportunisticAirlock;
use Symfony\Component\Semaphore\SemaphoreFactory;
use Symfony\Component\Semaphore\Store\RedisStore;

$redis = new Redis();
$redis->connect('127.0.0.1');

$seal = new SymfonySemaphoreSeal(
    factory: new SemaphoreFactory(new RedisStore($redis)),
    resource: 'site_capacity',
    limit: 20,
    ttlInSeconds: 30,
    autoRelease: false,
);

$airlock = new OpportunisticAirlock($seal);

$result = $airlock->enter($clientId);

if ($result->isAdmitted()) {
    // They're in. Do the expensive thing.
} else {
    // Full. Show a "please wait" page, return 503, etc.
}

What Just Happened?

1. A Seal was created — a semaphore allowing 20 concurrent users, backed by Redis.
2. An OpportunisticAirlock was wired up — first come, best effort, no queue.
3. enter() tried to acquire a slot. If capacity was free, the user got in. If not, they didn't.

That's the whole pattern. Every Airlock works the same way — you just swap the pieces.

Next Steps

• Core Concepts — understand the Seal + Strategy + Notifier model
• Strategies — pick the right admission strategy for your use case
• Recipes — real-world examples you can drop straight in