Architecture Intermediate

Service Discovery — jak se services najdou¶

Service DiscoveryMicroservicesConsul 3 min read

Mechanismy service discovery v mikroservisní architektuře. Client-side vs server-side discovery, Consul a Kubernetes DNS.

Proč Service Discovery?¶

V mikroservisách se services dynamicky spouštějí a zastavují. IP adresy se mění. Service Discovery solves: jak service A najde current adresu services B?

Client-Side Discovery¶

Klient se dotáže registru a sám rozhodne, na kterou instanci pošle požadavek.

const consul = require('consul')();
async function getServiceUrl(serviceName) {
    const services = await consul.health.service({
        service: serviceName, passing: true
    });
    const idx = Math.floor(Math.random() * services.length);
    const svc = services[idx].Service;
    return \`http://\${svc.Address}:\${svc.Port}\`;
}

Server-Side Discovery¶

Kubernetes uses server-side discovery natively:

apiVersion: v1
kind: Service
metadata:
  name: order-service
spec:
  selector:
    app: order-service
  ports:
    - port: 80
      targetPort: 8080
# Volání: http://order-service.default.svc.cluster.local

Tools¶

• Consul — health checking, KV store, multi-datacenter
• etcd — foundation Kubernetes
• Eureka — Netflix OSS, Java/Spring

Summary¶

V Kubernetes je service discovery vyřešená out-of-the-box. Mimo K8s zvažte Consul nebo Eureka.

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