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Discovering Services

Discovering Services

In this lesson, we will go through the discovery process of Services.

Discovering Services

Services can be discovered through two principal modes:

  • Environment variables
  • DNS

Every Pod gets environment variables for each of the active Services. They are provided in the same format as what Docker links expect, as well with the simpler Kubernetes-specific syntax.

Let’s take a look at the environment variables available in one of the Pods we’re running.

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POD_NAME=$(kubectl get pod \
    --no-headers \
    -o=custom-columns=NAME:.metadata.name \
    -l type=api,service=go-demo-2 \
    | tail -1)
kubectl exec $POD_NAME env

The output, limited to the environment variables related to the go-demo-2-db service, is as follows.

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GO_DEMO_2_DB_PORT=tcp://10.0.0.250:27017
GO_DEMO_2_DB_PORT_27017_TCP_ADDR=10.0.0.250
GO_DEMO_2_DB_PORT_27017_TCP_PROTO=tcp
GO_DEMO_2_DB_PORT_27017_TCP_PORT=27017
GO_DEMO_2_DB_PORT_27017_TCP=tcp://10.0.0.250:27017
GO_DEMO_2_DB_SERVICE_HOST=10.0.0.250
GO_DEMO_2_DB_SERVICE_PORT=27017

The first five variables are using the Docker format. If you already worked with Docker networking, you should be familiar with them. At least, if you’re familiar with the way Swarm ...

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