how to build DSN env from several ConfigMap resources? - kubernetes

Question

In order to a service work, it needs an environment variable called DSN which prints to something like postgres://user:password#postgres.svc.cluster.local:5432/database. This value I built with a ConfigMap resource:
apiVersion: v1
kind: ConfigMap
metadata:
name: idp-config
namespace: diary
data:
DSN: postgres://user:password#postgres.svc.cluster.local:5432/database
This ConfigMap mounts as environment variable in my service Pod. Since the values are different from user and password and these PostgreSQL credentials are in another k8s resource (a Secret and a ConfigMap), how can I properly build this DSN environment in a k8s resource yaml so my service can connect to the database?

Answer 1

Digging into Kubernetes Docs I was able to find. According to Define Environment Variables for a Container :
Environment variables that you define in a Pod’s configuration can be used elsewhere in the configuration, for example in commands and arguments that you set for the Pod’s containers. In the example configuration below, the GREETING, HONORIFIC, and NAME environment variables are set to Warm greetings to, The Most Honorable, and Kubernetes, respectively. Those environment variables are then used in the CLI arguments passed to the env-print-demo container.
apiVersion: v1
kind: Pod
metadata:
name: print-greeting
spec:
containers:
- name: env-print-demo
image: bash
env:
- name: GREETING
value: "Warm greetings to"
- name: HONORIFIC
value: "The Most Honorable"
- name: NAME
value: "Kubernetes"
command: ["echo"]
args: ["$(GREETING) $(HONORIFIC) $(NAME)"]