Health

Lets say there is a service that needs to be checked periodically if is running. Simplest solution would be to ping main site and if it responds with 200 everything is fine.

But, in reality service can not connect to database and response is served from outdated cache. Other case would be when everything works but mailing service is unreachable.

And this is where Health comes on stage. Health is an implementation of Health JSON Schema which standardises responses structure for monitoring endpoints.

How to use

Create instance of Health where all services requiring monitoring will be registered

use Health\Health;
use Health\Service\CallableService;

$health = new Health(
	'some-app',  // application name
	'healthy-server.com',  // host name
	'1.2.3',  // currently deployed version
	new \DateTime('2016-12-05T12:45:11+00:00')  // deployment date
);

$health->addService(
    'database',  // service group
    new CallableService(
        'postgres', // service name
        function () use ($pdo) { $pdo->exec('SELECT 1'); }, // validating function
        true // true if service is essential
    )
);

When all services were registered, Health can create status snapshots. Such snapshot can be used to expose service health as simple true/false endpoint:

$state = $health->state();
$state->isHealthy();  // returns true if all services are working
$state->summary(); // returns array with detailed information about all registered services

Example

In Symfony, for example

• /ping endpoint that returns 200 when essential services are working properly and 500 otherwise,
• /health endpoint that shows summary for all services, response status code is reflectin its health

class HealthController extends Controller
{
    /**
     * @Route("/ping", name="health_ping")
     */
    public function pingAction(): Response
    {
        return (new Response())->setStatusCode($this->get('health')->status()->isHealthy(true) ? 200 : 500);
    }

    /**
     * @Route("/health", name="health_summary")
     */
    public function healthAction(string $sku): Response
    {
        $status = $this->get('health')->status();

        $response = new JsonResponse();
        $response->setData($status->summary());
        $response->setStatusCode($status->isHealthy() ? 200 : 500);

        return $response;
    }
}