README

A PHP client for (Spring Cloud) Netflix Eureka service registration and discovery.

Installation

You can install this package easily using Composer:

composer require "piwvh/php-eureka"

Documentation

Create Eureka Client

The very first thing you need to do is to create an instance of EurekaClient using your configuration:

$client = new EurekaClient([
    'eurekaDefaultUrl' => 'http://localhost:8761/eureka',
    'hostName' => 'service.hamid.work',
    'appName' => 'service',
    'ip' => '127.0.0.1',
    'port' => ['8080', true],
    'homePageUrl' => 'http://localhost:8080',
    'statusPageUrl' => 'http://localhost:8080/info',
    'healthCheckUrl' => 'http://localhost:8080/health'
]);

List of all available configuration includes:

• eurekaDefaultUrl (default: http://localhost:8761);
• hostName
• appName
• ip
• status (default: UP)
• overriddenStatus (default: UNKNOWN)
• port
• securePort (default: ['443', false])
• countryId (default: 1)
• dataCenterInfo (default: ['com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo', 'MyOwn'])
• homePageUrl
• statusPageUrl
• healthCheckUrl
• vipAddress
• secureVipAddress
• heartbeatInterval (default: 30)
• discoveryStrategy (default: RandomStrategy)
• instanceProvider

You can also change configuration after creating EurekaClient instance, using setter methods:

$client->getConfig()->setAppName("my-service");

Operations

After creating EurekaClient instance, there will be multiple operations you can do:

• Registration: register your service instance with Eureka

$client->register();

• De-registration: de-register your service instance from Eureka

$client->deRegister();

• Heartbeat: send heartbeat to Eureka, to determine the client is up (one-time heartbeat)

$client->heartbeat();

You can register your instance and send periodic heartbeat using start() method:

$client->start();

With this method, first your service gets registered with Eureka using the configuration you have provided. After that, a heartbeat will be sent to the Eureka periodically based on heartbeatInterval configuration value. This interval time can be changed just like any other configuration item:

$client->getConfig()->setHeartbeatInterval(60); // 60 seconds

It's obvious that this method should be used in CLI.

• Service Discovery: fetch an instance of a service from Eureka:

$instance = $client->fetchInstance("the-service");
$homePageUrl = $instance->homePageUrl;

Discovery Strategy

When fetching instances of a service from Eureka, you probably get a list of available instances. You can choose one of them based on your desired strategy of load balancing. For example, a Round-robin or a Random strategy might be your choice.

Currently this library only supports RandomStrategy, but you can create your custom strategy by implementing getInstance() method of DiscoveryStrategy interface:

class RoundRobinStrategy implements DiscoveryStrategy {

    public function getInstance($instances) {
        // return an instance
    }
    
}

Then all you have to do, is to introduce your custom strategy to EurekaClient instance:

$client->getConfig()->setDiscoveryStrategy(new RoundRobinStrategy());

Local Registry and Caching

Failure is inevitable, specially in cloud-native or distributed applications. So, sometimes Eureka may not be available because of failure. In this cases, we should have a local registry of services to avoid cascading failures.

By default, if Eureka is down, the fetchInstance() method fails, so the application throws an exception and can not continue to work. To solve this problem, you should create a local registry in your application.

There is an interface called InstanceProvider which you can make use of. You should implement getInstances() method of this interface and return instances of a service based on your ideal logic.

class MyProvider implements InstanceProvider {

    public function getInstances($appName) { 
        // return cached instances of the service from the database 
    }
}

In this example, we have cached the instances of the service in the database and are loading them when Eureka is down.

After creating your custom provider, just make it work by adding it to the configuration:

$client->getConfig()->setInstanceProvider(new MyProvider());

Your custom provider only gets called when Eureka is down or is not answering properly.

That's it. By adding this functionality, your application keeps working even when Eureka is down.

For caching all available instances of a specific service, you can call fetchInstances() method which fetches all of the instances of the service from Eureka:

$instances = $client->fetchInstances("the-service");