Hello S2I World

This is just a small node.js Hello World app that I use to quickly demonstrate S2I builds in Openshift.

The process

1. In the Developer Catalog select "From Git"

2. In the resulting dialog fill in this git repo url, the builder image (Node.js), an application name for labeling, a name for resources, resource type DeploymentConfig, and create a route

3. [OPTIONAL] Add a pipeline if the option is available

4. Create the application

Note

The 'Application' and 'Name' fields may appear to be the same thing, but they are not. The 'Application' field creates labeling to group app resources. Specifically the app.kubernetes.io/part-of label in the DeploymentConfig. If you deploy a new app and give it the same 'Application' it will be part-of that application group.

The pipeline

You should see a 3 step pipeline if you added one. You will see the following steps

1. fetch-repository

2. build

3. deploy

The Service

In the Administrator perspective under 'Networking' or using the OC CLI you will see a new service

$ oc get svc
NAME                TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
hello-s2i-world   ClusterIP   172.30.123.214   <none>        8080/TCP   18m

Incidentally service names in OCP can be resolved by internal DNS.

<app-name>-<namespace>

Remembering that pods have limited applications, we have to use what is available to test the DNS resolution…​

From Inside the pod

sh-4.4$ echo -e "const dns = require('dns')\n\ndns.lookup('hello-s2i-world.hello-s2i-world', function(err, result) {\n\tconsole.log(result)\n})"|node
172.30.123.214

Note	The service name lookup resolved inside the pod to 172.30.123.214 which is what we see above from our OC client command

Internal DNS will always resolve service names this way.

The Route

In either the topology view in Developer mode or in the Networking section in Administrator view you can verify the application by clicking the route and opening it in a web browser.

The route will always be the same. It is always built with the following components:

http://<app-name>-<namespace>.apps.<cluster-name>.<base-domain>/

Example Route: http://hello-s2i-world-my-namespace.apps.mycluster.mydomain.net/