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Ambassador

For trying out this example you need to have access to a Kubernetes cluster, e.g. by choosing one of the options from INSTALL.

In this example we are creating a simple ambassador, which abstracts away a logging backend. The main random-generator service will log each incoming request by sending the generated data to an URL which is specified via the environment variable LOG_URL. Here we use this LOG_URL to call out to an Ambassador listening on localhost at port 9009. The Ambassador is free to forward the log data to an arbitrary log service.

For sake of simplicity we are just using as simple Ambassador which just logs the data to standard output. This ambassador uses a sime Node.js HTTP server and used from within the container image k8spatterns/random-generator-log-ambassador. This image can be found in the image directory (Dockerfile and Node.js code). It’s also directly available from Docker Hub.

Let’s create a bare Pod with k8spatterns/random-generator as the main container and k8spatterns/random-generator-log-ambassador as the ambassador:

kubectl create -f https://k8spatterns.io/Ambassador/pod.yml

A nodePort service helps for external access to the random generator:

kubectl create -f https://k8spatterns.io/Ambassador/service.yml

Now let’s access the service where we again assume that your cluster node’s have an external IP address which can be directly contacted from your desktop

port=$(kubectl get svc random-generator -o jsonpath={.spec.ports[0].nodePort})
# Use Minikube's IP or any external accessible node IP from your cluster
ip=$(minikube ip)
curl -s http://$ip:$port

We can now verify whether our Ambassador has been contacted with the appropriate data.

kubectl logs -f random-generator -c ambassador

You can also run this command in the background and re-run the curl program to see how the sidecar container is called in turn for each request.

This will result in an output like:

==========================================
Starting up random-generator Ambassador
Listening at http://localhost:9009
==========================================
Message received for processing:
>>> ID: d822e648-0f41-4c4f-ae3a-1ced14d2b4a2 -- Duration: 35318 -- Random: 355610385
Message received for processing:
>>> ID: d822e648-0f41-4c4f-ae3a-1ced14d2b4a2 -- Duration: 10080 -- Random: 294941020
Message received for processing:
>>> ID: d822e648-0f41-4c4f-ae3a-1ced14d2b4a2 -- Duration: 21987 -- Random: 1345536975