Planned lessonMID-036-L02

DNS-based discovery

On This Lesson 4 topics

This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.

In this lesson

use DNS names for service-to-service calls.

In Docker Compose, every service name is a DNS name on the Compose network: http://inventory:8080.
With several replicas, the name resolves to the replicas' addresses (Docker's internal DNS rotates among them).
Clients and JVMs may cache DNS results; check the JVM's DNS cache TTL and connection pooling (verify settings before recording).
Pooled keep-alive connections stay on one replica until closed, which skews balancing.
No library needed: configuration is just a hostname.

Draft outline details

yaml

services:
  inventory:
    image: shop/inventory
    deploy: { replicas: 3 }
  orders:
    environment:
      INVENTORY_URL: http://inventory:8080

What does orders need to know to reach inventory?

Show answer

Only the name inventory and the port.

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