How can I set JNDI configuration in a Docker overrides.yaml file?

Question

If I have a java configuration bean, saying:

package com.mycompany.app.configuration;

// whatever imports

public class MyConfiguration {

  private String someConfigurationValue = "defaultValue"; 

  // getters and setters etc
}

If I set that using jetty for local testing I can do so using a config.xml file in the following form:

  <myConfiguration class="com.mycompany.app.configuration.MyConfiguration" context="SomeContextAttribute">
    <someConfigurationValue>http://localhost:8080</someConfigurationValue>
  </myConfiguration>

However in the deployed environment in which I need to test, I will need to use docker to set these configuration values, we use jboss.

Is there a way to directly set these JNDI values? I've been looking for examples for quite a while but cannot find any. This would be in the context of a yaml file which is used to configure a k8 cluster. Apologies for the psuedocode, I would post the real code but it's all proprietary so I can't.

What I have so far for the overrides.yaml snippet is of the form:

env:
    'MyConfig.SomeContextAttribute':
      class_name: 'com.mycompany.app.configuration.MyConfiguration'
      someConfigurationValue: 'http://localhost:8080'

However this is a complete guess.

Answer 1

You can achieve it by using ConfigMap.

A ConfigMap is an API object used to store non-confidential data in key-value pairs. Pods can consume ConfigMaps as environment variables, command-line arguments, or as configuration files in a volume.

First what you need to create ConfigMap from your file using command as below:

kubectl create configmap <map-name> <data-source>

Where <map-name> is the name you want to assign to the ConfigMap and <data-source> is the directory, file, or literal value to draw the data from. You can read more about it here.

Here is an example:

1. Download the sample file:

wget https://kubernetes.io/examples/configmap/game.properties

You can check what is inside this file using cat command:

cat game.properties 

You will see that there are some variables in this file:

enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30r

2. Create the ConfigMap from this file:

kubectl create configmap game-config --from-file=game.properties

You should see output that ConfigMap has been created:

configmap/game-config created

You can display details of the ConfigMap using command below:

kubectl describe configmaps game-config

You will see output as below:

Name:         game-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
game.properties:
----
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30

You can also see how yaml of this ConfigMap will look using:

kubectl get configmaps game-config -o yaml

The output will be similar:

apiVersion: v1
data:
  game.properties: |-
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
kind: ConfigMap
metadata:
  creationTimestamp: "2022-01-28T12:33:33Z"
  name: game-config
  namespace: default
  resourceVersion: "2692045"
  uid: 5eed4d9d-0d38-42af-bde2-5c7079a48518

Next goal is connecting ConfigMap to Pod. It could be added in yaml file of Podconfiguration.
As you can see under containersthere is envFrom section. As name is a name of ConfigMapwhich I created in previous step. You can read about envFrom here

apiVersion: v1
kind: Pod
metadata:
  name: test-pod
spec:
  containers:
    - name: test-container
      image: nginx
      envFrom:
      - configMapRef:
          name: game-config

Create a Pod from yaml file using:

kubectl apply -f <name-of-your-file>.yaml

Final step is checking environment variables in this Pod using below command:

kubectl exec -it test-pod -- env

As you can see below, there are environment variables from simple file which I downloaded in the first step:

game.properties=enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30

Answer 2

The way to do this is as follows:

If you are attempting to set a value that looks like this in terms of fully qualified name:

com.mycompany.app.configuration.MyConfiguration#someConfigurationValue 

Then that will look like the following in a yaml file:

com_mycompany_app_configuration_MyConfiguration_someConfigurationValue: 'blahValue'

It really is that simple. It does need to be set as an environment variable in the yaml, but I'm not sure whether it needs to be under env: or if that's specific to us.

I don't think there's a way of setting something in YAML that in XML would be an attribute, however. I've tried figuring that part out, but I haven't been able to.